title: Does "The Brain Machine" work?

text:
# Question
Title: Does "The Brain Machine" work?
I came across this article on Make Magazine on "The Brain Machine" which will supposedly put one into a trancelike meditative state via a combination of sound and light pulses.

Is there any scientific evidence supporting the effectiveness of such a device?

I have not heard about any similar devices.

# Answer
You have to break down the question in two parts.

**(1) Is it possible to entrain brain oscillations by presenting oscillating lights or tones?**

Yes, it is possible to evoke "response phenomena" in the brain by presenting participants with oscillatory stimuli. The technical term for this phenomenon is "steady state evoked potential" and it was demonstrated for the visual (e.g., Herrmann, 2001) and as well as for the auditory domain (e.g., Zaehle et al., 2010).

(Please note that these references are only examples from one group. A more comprehensive overview can be found at PubMed.)

Thus, the devices you linked to might work in principle, that is, they might be able to entrain different brain oscillations.

**(2) Is it possible to put someone into a trancelike meditative state by entraining certain brain oscillations?**

It has been shown that the different frequency bands in which brain oscillations can be found are connected to perceptual and cognitive phenomena. (For a short introduction see Wikipedia on brain oscillations). Furthermore these frequency bands are not isolated, but the interweaving of these bands (i.e., cross-frequency coupling) is not fully understood yet (see for example Jensen & Colgin, 2007).

It has been shown, however, that the manipulation of brain oscillations can alter perception (see for example publications on phase resetting.)

In general, the topic of brain oscillations and its experimental manipulation is quite hot at the moment and receives a lot of attention, especially since new non-invasive methods for oscillatory brain stimulation are available (namely repetitive transcranial magnetic stimulation and transcranial alternating current stimulation). For a review, see Thut et al. (2011).

To come back to your initial question: no, I am not aware of any study connecting the entrainment of brain oscillations to trancelike meditative states. This, however, does of course not mean that there are no studies. Furthermore, that does not mean that you cannot reach meditative states while using this device. (Personally, I would think that you can reach meditative states with almost any stimulation - if you are good at mediation.)

> **References**
>
> Herrmann CS. (2001). Human EEG responses to 1-100 Hz flicker: Resonance phenomena in visual cortex and their potential correlation to cognitive phenomena. Experimental Brain Research, 137: 346-353.
> https://doi.org/10.1007/s002210100682
>
> Jensen O, Colgin LL. (2007) Cross-frequency coupling between neuronal oscillations. Trends in Cognitive Science 11(7):267-9.
> https://www.sciencedirect.com/science/article/abs/pii/S1364661307001271
>
> Thut G, Schyns GP & Gross J (2011) Entrainment of Perceptually Relevant Brain Oscillations by Non-Invasive Rhythmic Stimulation of the Human Brain. Frontiers in Psychology 2011; 2: 170.
> https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3142861/
>
> Zähle T, Lenz D, Ohl FW, Herrmann CS. (2010). Resonance phenomena in the human auditory cortex: Individual resonance frequencies of the cerebral cortex determine electrophysiological responses. Experimental Brain Research, 203, 629-635.
> https://doi.org/10.1007/s00221-010-2265-8
> 13 votes

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Tags: consciousness, meditation, devices
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# Question
Title: How does neural spiking begin in the fetus?
I'm interested in modeling human brain spiking activity. How does the very first spiking activity begin in the fetus?

I imagine all spiking activity is initiated by the senses and internal oscillators. Am I right? Or are there other initiators of spiking activity?

# Answer
> 11 votes
Many parts of the fetus brain begin showing neural activity before the senses that feed them are sufficiently developed to provide actual sensory information. In other words, it is unlikely that spiking activity in the brain is initiated by the senses. Some of the cells that become sensory organs, however, often fire in very specific patterns similar to the patterns they will use when they start actually sensing.

An example from Penn & Shatz (1999): in the human fetus, the connections from the eye to the visual cortex form before the retina is developed enough to respond to light. However, at this time the retinal ganglion cells spontaneously generate highly correlated bursts of action potentials. These bursts are similar to the sort of data they will generate once they actual start sensing, and these preliminary bursts allow the human fetus to start developing its visual cortex before it even has functional retina. This is not unique to humans, and similar activity was first observed in rats (Galli & Maffei, 1988).

The take away message, is that the cell in the brain start firing spontaneously before they has any sensory input. Some of this early firing is 'random' in the sense you asked before. However, neurons that develop into future sensory organs, tend to have their spontaneous firing resemble what their typical sensory production will look like in the future (once they start sensing). This allows the downstream circuitry to start adapting to the firing pattens before any real sensory infromation becomes available.

### References

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Tags: neuroscience, developmental-psychology, neural-network, theoretical-neuroscience
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# Question
Title: How can you limit excessive risk-taking at the institutional level?
Some firms have a compensation structure that encourages risk-taking while insulating employees from the bad consequences of their decisions. This creates the potential for moral hazard.

I started thinking about this because of what happened at AIG. For those unfamiliar with the situation, a small division (AIG Financial Products) in a huge insurance company was able to bankrupt the entire company. Incentives were very lop-sided for division management relative to the risks they were taking. Even though management was making millions, they were taking risks an order of magnitude larger than that. If they lost billions, they would only lose their future income (assuming they would be fired).

My question is, how do you align management/employee incentives at the institutional level in order to prevent this types of moral hazard?

Two things to note:

1. The situation at AIG is just an example. I'm not asking for solutions specific to AIG (e.g. limiting leverage) or financial firms in general. Many firms face this type of moral hazard with the CEO (i.e. a "golden parachute").
2. Aside from not being "at the institutional level", I doubt regulation is the answer. While there's a place for regulation, regulators seem to — at least initially — react to crises instead of prevent them (though there's no counter-factual for crises regulators may have prevented).

# Answer
Optimal contracting under moral hazard is an incredibly rich field. Any answer to your question would rely more on the assumptions being made about risk preferences, effort sets, etc. than any "universal solution" to moral hazard.

That being said, there are a couple of interesting pieces of the literature to note:

1. Optimal contracts often have a fixed component (the opposite of your "alignment" premise), with the variable component offered only insofar as it is required to induce more effort from the agent.
2. Optimal contracts use any information relevant to determining the effort expended by the agent, not just the result.

So I would think an answer would be to reduce (not increase) the amount of compensation variable upon the result and to condition compensation relative to other benchmarks that would indicate whether someone is just benefiting from tailwind.
> 4 votes

# Answer
I assume you meant to ask "**can** you align management/employee incentives to prevent these types of events from the institutional level?" Well in the simplest possible model which you seem to be familiar with, of course you can. But things are not so simple as they may seem at first, because incentivising exactly the right behaviour is hard.

For example, suppose that an employee has two tasks, A and B. A is observable but B is not. If you provide incentives to do job A well, the optimal response for the employee is to do as little of B as he can get away with. The moral is that unless all the contributions of an employee can be monitored, incentives can induce lopsided priorities for employees. If the aspect they are ignoring is crucial to the functioning of the organisation, the incentives will end up being counterproductive.
> 2 votes

# Answer
Investing is all about returns. Increasing returns in the short term is easy to do through taking on risk. Many institutions reward short term profits without considering any risks taken. This encourages irresponsible risk taking since the risk takers have nothing to loose.

One solution is to provide risk adjusted compensation instead of purely (short term) profit based compensation.

Another safeguard (that was put in place after the Great Depression in the USA) is to limit the size of financial institutions. Smaller institutions cannot take as large risks as larger ones. Unfortunately that legislated safeguard was removed back in 1997.
> 1 votes

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Tags: io-psychology, motivation, economics
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# Question
Title: Game-theory strategies to overcome holdout problem?
The hold-out problem often occurs in debt-restructuring or in urban development.

The hold-out problem is defined where an agent, for example a land developer, must negotiate with many lot owners and each lot owner must provide their consent in order for a project to proceed. However, since the agents know that their consent is required they can extract a portion of the producer surplus in excess of their opportunity costs. The net effect is that such large-scale projects are underproduced.

There are legal remedies to address this underproduction. Eminent domain is a legal tool to overcome hold-out problems, however, it does not consider pareto-efficiency. It's not at all clear whether developers that exercise eminent domain are increasing social welfare or simply have better influence over a political process to transfer resources from one group to another.

Ideally, we would like a voluntary bargaining solution that all (or most) parties agree to that produces a socially efficient amount. A bargaining solution should always be arrived at when the social utility of the production exceeds the opportunity costs of each individual and the producer cost.

What bargaining "game" could be designed (and enforced or enabled by a legal process) so that such a procedure could be applied to hold-out problems?

# Answer
The hold-out problem is much studied and has even been associated with IP disputes (especially relevant in an age where a complex device like a mobile phone can involve license agreements between hundreds of companies).

Some of the consequences being identified as a result of the hold-out problem include urban sprawl (easier to develop green-fields sites), urban decay (hold-outs prevent urban renewal), and even disruption of the innovation and investment cycle (hold-outs over-value their IP contribution and innovators then refuse to invest).

In Imminently Eminent: A Game Theoretic Analysis of Takings Since Kelo v. City of New London, Alex Hornaday proposes the following game:

* Game participants include a Developer and an Owner;
* Developer values Owner's property at $x$;
* Owner values property in a range $p\_1$ to $p\_2$ such that $p\_1 \< x \< p\_2$;
* Basic play:
    1. Developer offers price $x\_1$;
    2. Owner either accepts or rejects $x\_1$;
    3. if Owner rejects $x\_1$, Developer may quit bargaining or offer price $x\_2$;
    4. if Developer offers price $x\_2$, Owner either accepts or rejects $p\_2$;
    5. if Owner rejects $x\_2$ and the Developer has the power of eminent domain, Developer may then choose either to do nothing or to condemn;

Hornaday also includes a penalty which the Owner would incur during round 2. He acknowledges that much of this is Pareto-inefficient as either (or both) parties are forced into a loss following an unsatisfactory conclusion.

The oversimplification here is that hold-outs tend to occur when multiple parties need to negotiate. In that case the last part to negotiate a deal is able to exert a monopoly pricing power over the other parties.

Eminent domain certainly offers the eventuality of a result (from the Developer's perspective) but can be distortionary (since either party may have insufficient negotiating power to secure an ideal result).

My answer, at this point, becomes speculative and I offer this untested as a potential model for achieving a "better" response amongst multiple parties. It is based on the concept of optimal reservation prices in auctions.

Supplementing Hornaday's game as follows:

1. Developer makes a sealed reserve offer, $r\_1$, for all properties from all Owners;
2. All Owners make a sealed pooled reserve request, $r\_2$, for all properties;
3. Negotiator establishes whether $r\_1$ and $r\_2$ are aligned;
4. If not, then an assessment (legal and social) must take place (at Developer's expense) if the Developer wishes to continue to assess whether eminent domain is even possible (not a decision, however, so pertaining to a negotiation only);
5. If negotiation is possible, or if eminent domain is a viable solution to negotiation, then price negotiation can continue with all parties knowing where they stand.

We can now continue with the original game. I believe that there need to be sufficient inducements and penalties for the Owners (inducements for early settlement, penalties for holding out) to balance the Developer's costs in the process.

Obviously, if the reserve prices make a settlement unlikely and eminent domain would not be possible, then the Developer must walk away and pocket the costs of the process to that point.
> 7 votes

# Answer
If you're looking for a simple game, for example to teach the holdout problem to students just beginning game theory, you could do worse than start with a general prisoner's dilemma (PD) game. The 30-second explanation is that it only makes (rational) sense for one player to act if the other person is acting as well.

The holdout problem is a motivation for voluntary contribution mechanism experiments (VCMs) or "public goods" games, which is an example of a PD game in public context.

These games only speak to the private optimum of holding out (the unilateral optimum) as compared to the social optimum of cooperating (the multilateral optimum), and doesn't speak to extracting surplus. Cooperation can be ensured with contracts and other extra-game mechanisms, usually relying on the possibility of negotaition and requiring enforcement of contracts. Starting with a simple PD, including side-payments explicitly in the game structure should be sufficient for capturing the flavor of surplus extraction.

**Update:** Miceli has recently published a noncooperative game model for the holdout problem in *Public Choice* as "Free riders, holdouts, and public use: a tale of two externalities".
> 4 votes

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Tags: io-psychology, decision-making, economics, game-theory
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# Question
Title: What are the key algorithms for learning optimal behavior of economic agents?
I'm playing around with social learning of near-optimal behavioral rules on a set of agents. The idea is roughly that given an income process (or technology process, depending on the question) an optimal nonlinear, intertemporal policy rule exists. Assume this rule can be approximated closely by a linear function. Agents would like to learn this policy rule, and a first pass is to have them learn the rule simply by experimentation. "In autarky," i.e. without any information exchange with other agents, an agent would try a rule for some time, use some metric to determine how well it does against other rules he/she has tried, and perhaps reassess, perhaps try an entirely different rule via experimentation. This agent only observes his/her own history.

A second pass is to allow the agent access to all other agents' histories. Presumably this would speed up learning. A third pass might be to put these agents on an information network of some sort.

I've been perusing literature on social learning, but am not entirely sure the frameworks I am looking at are exactly what I want. Many of them appear to be Bayesian learning about a hidden state of nature, for which everyone has a private signal. I'm actively reviewing literature right now, but as I do, does anyone have any thoughts/suggestions?

# Answer
Take a look at POMDP's \- partially observable markov decision processes.

If you have a value function (income) that is known for agents in various states, and you are trying to identify the optimal policy then Bellman's equation which is at the heart of POMDP's will help you identify this policy.

These tools are part of a class of re-inforcement learning algorithms (in fact, they are used quite often for robotics). So they map very neatly to the framework you have identified (agents, a reward function, and a state/action space)

Another angle of attack would be using genetic algorithms in your optimization procedure.
> 4 votes

# Answer
Here are two computational approaches which might work:

I. **Artificial neural network**

A neural network consists of an interconnected group of artificial neurons, and it processes information using a connectionist approach to computation. In most cases an ANN is an adaptive system that changes its structure based on external or internal information that flows through the network during the learning phase. Modern neural networks are non-linear statistical data modelling tools. They are usually used to model complex relationships between inputs and outputs or to find patterns in data. Perhaps the greatest advantage of ANNs is their ability to be used as an arbitrary function approximation mechanism which 'learns' from observed data. However, using them is not so straightforward and a relatively good understanding of the underlying theory is essential.

* **Choice of model:** This will depend on the data representation and the application. Overly complex models tend to lead to problems with learning.
* **Learning algorithm:** There are numerous trade-offs between learning algorithms. Almost any algorithm will work well with the correct hyper-parameters for training on a particular fixed dataset. However selecting and tuning an algorithm for training on unseen data requires a significant amount of experimentation.
* **Robustness:** If the model, cost function and learning algorithm are selected appropriately the resulting ANN can be extremely robust.

II. **Support vector machine**

A set of related supervised learning methods that analyse data and recognize patterns, used for classification and regression analysis. The standard SVM takes a set of input data, and predicts, for each given input, which of two possible classes the input is a member of, which makes the SVM a non-probabilistic binary linear classifier. Since an SVM is a classifier, then given a set of training examples, each marked as belonging to one of two categories, an SVM training algorithm builds a model that predicts whether a new example falls into one category or the other. Intuitively, an SVM model is a representation of the examples as points in space, mapped so that the examples of the separate categories are divided by a clear gap that is as wide as possible. New examples are then mapped into that same space and predicted to belong to a category based on which side of the gap they fall on.

Neural Networks have been used to create highly competitive computer-players for the open-source FreeCiv. There, Neural Networks are used with Monte Carlo Methods which I've also used in simulating economic interactions in games.

Not sure if this is entirely what you're looking for but might be a start?
> 5 votes

# Answer
Many key algorithms are summarized on the **ACE Research Area: Learning and the Embodied Mind** website.

*ACE* = Agent-based Computational Economics
> 1 votes

# Answer
This paper by Glazer and Rubinstein, while not strictly relevant to your research, uses a particular algorithmic model of agent behaviour and analyses its effect on the implementability of different mechanisms. The algorithm itself might be of interest to you - I think variants of it could be both realistic and easy to use in applied models.
> 1 votes

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Tags: learning, reference-request, social-psychology, game-theory, agent-based-modeling
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# Question
Title: Do safety features cause drivers to engage in more risky behavior than they otherwise would?
It seems to be generally assumed that making cars safer for the occupants will reduce death, injury, and damage from traffic accidents.

What are some examples of significant empirical research on this topic? Specifically, do safety features cause drivers to engage in more risky behavior than they otherwise would? If so, what is the net effect of additional safety mechanisms?

# Answer
Any review in this area should start with Peltzman's 1975 JPE article. Peltzman was writing a few years after the 1968 Motor Vehicle Safety Act (U.S.) went into effect. The act required, among other things, padded dash boards and seat belts. He says (p. 717):

> The one result of this study that can be put forward most confidently is that auto safety regulation has not affected the highway death rate. Neither the time-series nor cross-section data permit any other conclusion. However, these data are not as decisive about what underlies this result. On one interpretation, safety regulation has decreased the risk of death from an accident by more than an unregulated market would have, but drivers have offset this by taking greater accident risk.

In general, the idea is that seat belts and other safety devices may save lives *if the accident rate is held constant*, but that in reality, wearing a seat belt may induce more risk taking and thus more accidents overall (moral hazard, or Peltzman's "compensating behavior"). Then, it is not obvious whether more accidents which are, on average, less fatal will result in more deaths overall.

Of course, Peltzman didn't settle the matter. More recently, Cohen and Eniav (2003) found the opposite--that safety devices unambiguously save lives and that there is no evidence of additional risk-taking by seat belt wearers. Levitt and Porter (2001) came to a similar conclusion (this later paper is worth reading because it brings to light the issue of sample selection problems (à la Heckman), and a way of correcting for it). It seems, at least for seat belts, that the matter has been settled by these later papers. But, these lines of research highlight that, in general, we cannot say for certain what the net effect of safety regulations will be *a priori*.

Interestingly, the Cohen paper focuses on *primary enforcement*, that is, providing incentives to use safety devices (or, rather, disincentives for not using them) beyond the live-saving benefits. This would tend to cause people who wouldn't ordinarily use safety devices to use them. **If** it is true that drivers are compensating for their unsafe behavior by using safety devices, then more safe drivers would be induced to use the devices and the moral hazard may be somewhat offset. This tends to indicate that non-optional safety improvements may have a larger impact on deaths per mile than optional safety improvements.

Oh, and here is the spiked steering wheel comic you are looking for.
> 13 votes

# Answer
Someone asks a related question of a Nobel Prize Winner in Economics in a public forum (who was speaking off the record).

His opinion was yes, because the fundamental issue was that human beings had a certain tolerance level for "accidents," so that if you make cars safer, people would drive more recklessly with the safer vehicles, until the accident rate reached the old, tolerated levels.

At least this was the example he used to illustrate his point. The original question was did financial reforms over the past century/decade/year make the financial system safer.
> 0 votes

# Answer
I think it varies by safety equipment, and that you'll get different results for anti-lock brakes (like the famous Munich taxi cab study) or air-bags.
> 0 votes

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Tags: io-psychology
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# Question
Title: What is a good book for studying incentives?
I am looking for a book, which gives a broad overview of all the main theories regarding incentives. Using this book, I would like to further my understanding of things like:

* Why slot machines keeps people motivated to play
* Why extrinsic motivation is weaker than intrinsic motivation

Economical theories should at least contribute to the understanding of incentives.

# Answer
> 6 votes
I guess what you are looking for is readings on applied behavioral economics. Here is a popular favourite: Freakonomics

# Answer
> 5 votes
If you want to delve deeper into the topic, If Homo Economicus Could Choose His Own Utility Function, Would He Want One with a Conscience? is a seminal paper. Then, you can take a look at some of Bob Frank's other publications. Among them, I would recommend Passions Within Reason and Winner Take All Society.

# Answer
> 5 votes
The aspects of incentives which you are interested in are studied by psychologists as well. I recommend Carol Dweck's work. One of her popular books is Mindset.

# Answer
> 1 votes
You could check out any of Dan Ariely's books. Those are generally good at providing a similar to Freakonomics-level handling of a variety of economic topics, especially behavioral ones.

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Tags: reference-request, io-psychology, motivation, economics
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# Question
Title: Why is training better when following an easy-to-difficult schedule?
As suggested in the answer to this question, experimental results show that training is most effective when it follows an easy-to-difficult schedule.

**What theories and specifically computational models account for that?**

In the simple computational models commonly used to demonstrate learning classifications for example, there is no such effect, as far as I know:

* Binary Perceptron \- Typical examples (closest to the cluster means, or far apart along the optimal separating vector) are the most informative, leading to a prediction that **easy trials would result in faster learning**.
    + Some learning algorithms only update the network when an error is made, leading to a prediction that **more difficult trials would result in faster learning**.
* Support Vector Machinces (SVM) - only the few most difficult examples affect the final result, again leading to a prediction that **more difficult trials would result in faster learning**.
* Naive Bayes classifier \- Typical examples help estimating the parameters with less errors, leading to a prediction that **easy trials would result in faster learning**.

# Answer
SVM training is typically done in a batch processing, and thus the order of data presentation doesn't matter. You should consider **online learning algorithms**, for example, the perceptron learning rule. These algorithms are in general stochastic gradient descent optimization procedures, and easy examples early on with larger learning step would be much more efficient (faster convergence towards the correct answer) than learning with difficult examples first.
> 10 votes

# Answer
Another way of thinking about this is that by progressing easy-to-hard, different intermediate knowledge structures are called into existence in the course of processing. These knowledge structures, built from an agent's encounter with easy problems, can prove useful in its encounter with subsequent and more difficult problems.

This idea has been around for a long time in a variety of cognitive traditions. It's intimately related to developmental theories of, for instance, Piaget, and Mandler (2006); and to the schema literature, which is vast, but of which Minsky (1986) and Schank & Abelson (1977) are exemplars.

This is all very vague, though. The best (or at least, the most precise) way to think about knowledge progression is through hierarchical reinforcement learning. The idea there is that most non-trivial tasks are inherently hierarchical; and so learning how to do a task requires one to learn how to do its constituent sub-tasks. The more tasks you learn how to do, the greater the 'toolbox' you will be able to bring to subsequent tasks.

With regard to the original question, easier examples of some task induce the acquisition of the controllers (knowledge structures) that will aid the performance of later, more complicated, tasks, and the acquisition of later and more complicated knowledge structures. Oudeyer et al. (2007) and Barto (2009) describe this process in detail, the former using a situated robotic agent. (If we replace 'controllers' with 'rules' then the process becomes comparable to the rule search and chunking process used in ACT-R and Soar, as mentioned in Jeromy Anglim's answer)

# References

> Barto, A. (2009). Skill characterization based on betweenness. In Advances in Neural Information Processing Systems 22.
>
> Mandler, J. M. (2006). The Foundations of Mind: Origins of Conceptual Thought. Oxford University Press, USA.
>
> Minsky, M. (1986). Society of mind. New York, NY: Simon & Shuster.
>
> Oudeyer, P.-Y., Kaplan, F., & Hafner, V. V. (2007). Intrinsic motivation systems for autonomous mental development. Ieee Transactions on Evolutionary Computation, 11(2), 265–286.
>
> Schank, R., & ABELSON, R. (1977). Scripts, plans, goals and understanding: An inquiry into human knowledge structures.
> 7 votes

# Answer
*Interesting question. I've written up a discussion of the model-based training literature and how it relates structuring task difficulty with practice. That said, I feel it's only a start and my apologies that it is more pitched at cognitive tasks than perceptual tasks.*

### A summary of model-based training systems

Fu et al (2006) have a paper on *real-time model-based training systems*, in which they review some of the work on model-based training systems:

> There has been a long history of applying cognitive theory of learning and skill acquisition to model-based training systems (e.g., Anderson et al., 1995; Graesser et al., 2004; Hill and Johnson, 1993; Sleeman and Brown, 1982). The key idea of a model-based training system is that instructions should be given based on a cognitive model of the competence that the trainee is being asked to learn. In other words, the cognitive model should incorporate the underlying skills that allow the model to per- form the task the trainee is expected to perform. Based on the model, the system can monitor actions of the trainee and infer the intentions of the trainee by mapping actions of the trainee to components of the model. In other words, a model of com- petence provides an explanation of actions as trainees interact with the system. Immediate feedback or real-time instructions can then be given to the trainee to facilitate learning.

### John R. Anderson and colleagues on cognitive tutors using the computation model ACT-R

Anderson et al (1995) summarise their work on cognitive tutors teaching LISP programming , geometry and algebra. Their system incorporates eight instructional design principles a few of which pertain to task difficulty.

First, let's look at the design principles:

> 1. represent student competence as a production set
> 2. communicate the goal structure underlying the problem solving
> 3. provide instruction in the problem-solving context
> 4. Promote an abstract understanding of the problem-solving knowledge
> 5. Minimise the working memory load
> 6. Provide immediate feedback on errors
> 7. Adjust the grain size of instruction with learning
> 8. Facilitate successive approximations to the target skill

I think principles 5 and 8 directly relate to structuring task difficulty with practice, and probably others relate more indirectly. Minimising working memory (i.e., principle 5) requires providing instruction in manageable components. Facilitating successive approximations (i.e., principle 8) involves progressively providing less support to the learning and is an example of increasing task difficulty with practice.

### References

* Anderson, J.R., Corbett, A.T., Koedinger, K.R., Pelletier, R., 1995. Cognitive tutors: lessons learned. The Journal of the Learning Sciences 4, 167–207. PDF
* Fu, W.-T., Bothell, D., Douglass, S., Haimson, C., Sohn, M.-H., & Anderson, J. A. (2006), Toward a Real-Time Model-Based Training System. Interacting with Computers, 18(6), 1216-1230. PDF
* Graesser, A.C., Lu, S., Jackson, G.T., Mitchell, H., Ventura, M., Olney, A., Louwerse, M.M., 2004. Auto tutor: a tutor with dialogue in natural language. Behavioral Research Methods, Instruments, and Computers 36, 180–193. PDF
* Hill Jr., R.W., Johnson, W.L., (1993). Designing an intelligent tutoring system based on a reactive model of skill acquisition. Proceedings of the International Conference on AI and Education, Edinburgh, 1993.
* Sleeman, D., Brown, J.S., 1982. Intelligent Tutoring Systems. Academic Press, New York.
> 6 votes

# Answer
The basic effect can be accounted for by connectionist models. See for example Suret & McLaren (2002). To quote the abstract:

> This paper details an associative model that is applied to human learning on an artificial dimension. A variety of phenomena, including peak-shift, transfer along a continuum and summation / generalization are considered and simulation results are presented that give a close fit to empirical data.

http://faime.demon.co.uk/~streetm/wcci\_2002/IJCNN02/PDFFiles/Papers/1163.pdf
> 2 votes

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Tags: learning, computational-modeling, perceptual-learning
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# Question
Title: Does self-rated performance predict objective performance over and above other-rated performance?
**Context:** I was at a talk today where data was presented where a group of sports people ranked their own performance and everyone else in the group. This enabled self-rated performance to be correlated with the average of other-rated performance. The general observation was that there was a strong relationship between the two variables, but that where self-rated performance deviated from other-rated performance, people tended to rate themselves higher.

This raises the question of what this self-other discrepancy represents. One answer is that people have a self-serving bias. Another answer is that people have unique information about themselves.

**Question:** Thus, I'm interested in studies that have looked at what self-rated performance predicts over and above other-rated performance. In particular:

**To what extent does self-rated performance predict objective performance over and above other-rated performance?**

I imagine these findings would vary as a function of a range of factors including type of task, number of rated used form the other-rating, and so on. But at first instance, I'd be interested in any empirical examples.

# Answer
> 10 votes
I don't know of a study that tries to answer your specific question but you might want to have a look at illusory superiority, "a cognitive bias that causes people to overestimate their positive qualities and abilities and to underestimate their negative qualities, relative to others" (wikipedia).

I can especially recommend the paper by Dunning and Kruger (1999): Unskilled and unaware of it: How difficulties in recognizing one's own incompetence lead to inflated self-assessments (also the winner of the ignoble price for psychology, 2000). In this paper the authors show that people who are competent in a certain domain are pretty accurate in predicting their performance in this domain (compared to objective standards). On the other hand, people who are incompetent typically overestimate their performance (i.e., predict to perform good, whereas they perfom poorly). This overestimation is mainly driven by their lack of knowledge about that domain. If they are taught that they are poor performers, their prediction goes in line wit their actual performance.

These results could explain your observation of self-other discrepancy, as others might have more knowledge about how to accurately predict performance than the poor perfomers who over-rate their performance.

Reference:

Kruger, J., & Dunning, D. (1999). Unskilled and unaware of it: How difficulties in recognizing one’s own incompetence lead to inflated self-assessments. *Journal of Personality and Social Psychology*, 77(6), 1121–1134. doi:10.1037/0022-3514.77.6.1121

# Answer
> -1 votes
Self rated intelligence is garbage.

See

Paulhus DL, Lysy DC, Yik, MSM (1998), Self-Report Measures of Intelligence: Are They Useful as Proxy IQ Tests?. Journal of Personality, 66: 525–554. doi: 10.1111/1467-6494.00023

To quote the abstract:

> Correlations between single-item self-reports of intelligence and IQ scores are rather low (.20–.25) in college samples. The literature suggested that self-reports could be improved by three strategies: (1) aggregation, (2)item weighting, and (3) use of indirect, rather than direct, questions. To evaluate these strategies, we compared the validity of aggregated and unaggregated versions of direct measures with four indirect measures (Gough’s Intellectual efficiency scale, Hogan’s Intellect composite scale, Sternberg’s Behavior Check List, and Trapnell’s Smart scale). All measures were administered to two large samples of undergraduates (Ns = 310, 326), who also took an IQ test. Although results showed some success for both direct and indirect measures, the failure of their validities to exceed .30 impugns their utility as IQ proxies in competitive college samples. The content of the most valid items referred to global mental abilities or reading involvement. Aggregation benefited indirect more than direct measures, but prototype-weighting contributed little.

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Tags: performance, social-psychology, io-psychology, bias
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# Question
Title: Do students exhibit rational behavior in determining study time?
While I teach some economics classes, I must admit to near complete ignorance on the optimization processes students undertake when studying. We often say that the "best" students are those who earn the highest grades. However, from (naive) economic first principles, a rational student might be expected to endeavor not to maximize her grade, but rather to study until the marginal benefit of additional study equals its cost. Thus, we view students as grade producers who transform labor into grades.

**Have there been any studies that investigate the optimization problem these "grade producers" are solving when they choose how much to study (and especially on how they assess the benefits of grades)?**

# Answer
I think this is a very interesting question that I'm not sure we know the answer to. As we move towards online-based instruction, the question of whether students "optimally" determine their study time is extremely relevant. For instance, if students are allowed to "self-pace" themselves, will they do so optimally? Going to lectures in part may serve as a "commitment device" to go to class.

The only good economic study I know of is by **David Figlio et al** "Is it Live or is it Internet?: Experimental Estimates of the Effects of Online Instruction on Student Learning". It also has the virtue of (attempting) to be a randomized controlled trial. However, I'm sure that there are probably other behavioral economics or psychology studies worth visiting.

The authors write,

> "Without the nudge of having to attend classes, the authors suggested, it can be easy to let recorded lectures pile up unwatched. Indeed, it is common at Florida to see students in libraries cramming viewings of a dozen lectures back to back before exams."

Here is a link to the paper (gated, unfortunately): http://www.nber.org/papers/w16089

Also a popular press description: http://www.nytimes.com/2010/11/05/us/05collegeside.html
> 8 votes

# Answer
### Relationship between study time and performance

Plant et al (2004) review the literature of studies that have correlated average time spent studying and variables such as GPA. They report a couple of correlational studies in the literature that found small positive correlations (e.g., $r=.18, r=.23$). They make two main points: (a) academic performance is heavily influenced by knowledge, skills and stable abilities that a student brings to the subject. (b) Study effectiveness is more than just time spent, it is related to how the student studies (with Plant et al suggesting the importance of deliberate practice).

However, there are several reasons why these small correlations may not reflect the true importance of study time for the individual decision maker. (a) Self-regulatory variables may lead people to increase time spent when they are having difficulty and decrease time spent when they find a subject easy. (b) The relationship between time spent and grade for a given individual may be non-linear (e.g., at first, more time spent may readily yield higher grades, but at a point, the rate of increase may dramatically slow approaching an asymptote). (c) variation in time spent may be somewhat low. (d) measures of time spent may be somewhat unreliable. (e) Controlled cognitive psychology experiments and the expertise literature show the huge role of practice in improving performance.

### Psychological theories of study time

Zimmerman et al (1994) review the literature on theories of allocation of study time. They mention aptitude-trait, operant, information processing, and metacognitive views. They focus mainly on the sociocognitive perspective and discuss the roles of planning, goal setting, and self-efficacy in influencing time regulation. You may also want to check out perceptual control theory and the work by Jeffrey Vancouver.

In summary, such models tend to be more qualitative in their description of human behaviour. They also suggest that the allocation of study time is not performed by a perfectly rational actor. Rather, effective allocation quality and quantity of study time is a skill.

*This is the result of a literature search. I didn't find anything that specifically modelled study time as the optimisation of an explicit function. But such research may well be out there, and I agree that such a model would be interesting.*

### References

* Plant, E.A. and Ericsson, K.A. and Hill, L. and Asberg, K. (2005). Why study time does not predict grade point average across college students: Implications of deliberate practice for academic performance. Contemporary Educational Psychology, 30, 96-116. PDF
* Zimmerman, B.J. and Greenberg, D. and Weinstein, C.E. (1994). Self-regulating academic study time: A strategy approach. Self-regulation of learning and performance: Issues and educational applications, 181--199. GOOGLE BOOKS
> 6 votes

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Tags: io-psychology, motivation, rationality, educational-psychology
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# Question
Title: Is there any evidence to support a correlation between how much bodily energy you are using, and how quickly time appears to pass?
It seems to me that time passes more slowly when I am drinking coffee, but when I stop, or I am tired it seems that time passes a lot faster.

Could this have something to do with the sampling rate at which the life-loop in my brain can perceive things? Since a higher sampling rate in this life-loop would cause more time to be perceived?

# Answer
There's literature on temporal expansion with vigilance. Perhaps this might get you started.

Tse, P. U., Intriligator, J., Rivest, J., and Cavanagh, P. (2004). Attention and the subjective expansion of time. *Perception & Psychophysics*, *66*(7):1171–1189.

In this instance they're looking at how odd, unique, or surprising events might increase the amount of attention applied and that those events seem to last longer than othewise very comparable ones. The literature reviews speaks a bit to what you've asked about.
> 10 votes

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Tags: perception, time, physiology
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# Question
Title: Is there experimental support for John Perry's "Theory of Structured Procrastination"?
John Perry's theory of structured procrastination can be summed up as follows:

1. Some people are inherently predisposed to be procrastinators across a wide range of domains
2. Such procrastinators are still capable of being productive
3. They can achieve this because they work on less-important (but still important) tasks in order to avoid working on (procrastinate) on more-important (or seemingly more important) tasks.
4. If you are a procrastinator and want to still get things done, expand your workload/to-do list.

The first point seems to be well supported since procrastination is regarded in the literature as a personality trait (Steel, 2007). The second point also seems reasonable, although I am not sure of empirical support for it (although I can think of plenty of anecdotal evidence). The real interest for me, is the mechanism proposed in the 3rd and 4th point. (Note that Perry is not the only one to propose such a theory, see for instance Aaron Swartz' HOWTO: Be more productive.)

**Has it been observed that procrastinators who are successful achieve this success by expanding their workload and working on medium importance task at the cost of high importance tasks they want to procrastinate on?**

### References

Steel, P. (2007) "The nature of procrastination: A meta-analytic and theoretical review of quintessential self-regulatory failure." Psychological Bulletin 133(1): 65–94. \[pdf\]

# Answer
> 19 votes
In short, no. Perry's essay is amusing and compelling, but incomplete. Procrastination is an epiphenomenon of motivation, an active area of research which has some models relevant to the study of procrastination, such as:

Perry emphasizes task importance as the metric that keeps a task unfinished and at the top of a structure procrastinator's to-do list. The truth is more complicated and not an entirely resolved area of research. Delayed gratification, immediate discomfort, and the procrastinator's prediction of probability of reward are some of the additional factors that determine which task a structured procrastinator will work on at a given time.

Over time, the least-desirable tasks often remain unfinished, seem increasingly important, and thus move to the top of the to-do list.

### References

> * Laibson, D. (1997). Golden Eggs and Hyperbolic Discounting. Quarterly Journal of Economics 112(2): 443–477.
> * Steel, P., König, C. (2006) Integrating theories of motivation. Academy of Mgmt. Rev. 31(4): 889-913.

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Tags: reference-request, motivation, io-psychology, procrastination
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title: How to estimate IQ for public figures?

text:
# Question
Title: How to estimate IQ for public figures?
**Background:** I read a question on Quora that asked how intelligent is Barack Obama. A wide range of arguments were presented. The tone of the answers was not neutral because of the political context of the question. Furthermore, over the while I've read estimates of intelligence of various famous people from history (e.g., scientists, presidents, etc.). Issues were also raised about how intelligence is defined (e.g., cognitive, social, emotional or physical; achievement versus latent ability, etc.) Despite these issues, I find the topic interesting.

### Questions:

* **If you cannot administer a standardised intelligence test to someone, to what extent can you obtain a good estimate of their IQ from the kinds of information available about public figures?**
* **What is considered scientific best-practice in this regard?**
* **How accurate is best practice? Do any studies provide validity estimates (e.g., correlating estimates with actual IQ test scores)?**

In relation to public figures, a wide range of information is often available: e.g., demographics, educational attainments, career achievement, writing samples, personal achievements, samples of public speaking, and so on. Sometimes, information such as school and university grades will be available. Of course, a lot of this information will be non-standardised. I wonder what would be a good way to collect and synthesise this information to generate a prediction.

# Answer
### Entry into the literature

As a starting point, Simonton (2009) provides an excellent introduction to the field of *historiometric assessment of intelligence*. To quote the abstract:

> Running parallel to mainstream research on the psychometric assessment of intelligence is another tradition of research on the historiometric assessment of intelligence and closely affiliated variables. Historiometric assessment is based on four data sources: (a) personality sketches (e.g., Intellectual Brilliance), (b) developmental histories (e.g., IQ), (c) content analyses (e.g., integrative complexity), and (d) expert surveys (e.g., Openness to Experience). The first two represent major lines of intelligence research that involved key figures in the development of corresponding psychometric methods (e.g., Galton, Terman, and Thorndike), whereas the last two constitute independent research paradigms that later intersected with the first two. The literature on U.S. presidents then provides an integrated illustration of the four historiometric approaches and how they converge on the same broad conclusions. Significantly, historiometric investigations on the relation between broadly defined intelligence and adulthood achievement obtain about the same effect size as that found in psychometric research (i.e., $r$ or $\beta$ .25 $\pm$ .10). Because historiometric and psychometric studies have rather distinctive methodological advantages and disadvantages, this consistent outcome provides corrobora- tive support for both sets of empirical findings.

The review summarises various studies aiming to assess intelligence of royalty, U.S. politicians, and eminent figures.

### Critical thoughts

For current and recent public figures substantial additional information would be available. In particular, many powerful predictors of IQ would often be available including university grades, scores on standardised assessments, SAT scores and so on. Furthermore, the existing literature on IQ correlates is huge and provides substantial information that could inform predictive models of IQ prediction. In contrast where such models are applied to the past, the predictive power of such models may be wrong.

I'd also be extremely wary of estimates of intelligence that yield estimates like 200 (i.e., around 7+ standard deviations above the mean). E.g.,

> After comparing the chronological age in which .. achievements appeared with the mental age that they represented, Terman decided that Galton’s IQ must have been close to 200. (Simonton, 2009, p. 319)

The expertise literature has highlighted the importance of not confusing eminence with IQ. Eminence is substantially influenced by years of practice, training, focus, opportunity, and luck. IQ is useful, but the correlation between IQ and eminence is insufficient to yield the kind of certainty in prediction to result in IQ predictions above something like 3 or perhaps 4 standard deviations above the mean (i.e., 145 to 160).

### References

* Simonton, D.K. (2009) The “other IQ”: Historiometric assessments of intelligence and related constructs. *Review of General Psychology*, 13, 315.
> 7 votes

# Answer
This is just my personal thought process.

The way to measure the IQ of public figures/persons in leadership positions differ than that of the IQ being measured for normal individuals. Traditionally, IQ is being represented as the Intelligence of a person in analytic/cognitive skills. Later Gardner developed the famous multiple facets of intelligence by which intelligence could be approached from multiple paradigms. This seems to be good from an individual perspective.

In case of public figures, the impact of change(probably good change) brought by them upon the group represented by them, whether it be organization or a country, should be the priority factor in estimating the IQ. Thus measuring the IQ of those figures must always be a complex model that measure the effect of change that they brought to their group as a result of them being the mentor of the group. This may sound odd, but this is what often termed as political will or lack of it in common parlance. So the IQ of a leader can be assessed by the positive changes they have made to their environment.

So going by Stenberg's Triarchic Theory of Intelligence,

* Scientists' IQ may be measured by Analytic Intelligence
* Artists' IQ may be measured by Creative Intelligence
* Public/Leaders IQ may be measure by Practical Intelligence

Personally, I feel the dimension of change (Obama always speak about change, hope he doesn't think of a change in President this time :) ), must be the biggest factor in evaluation since the decision of a leader is bound to have a impact on a large number of people. It may even change over time if the impact is felt over a long period of time. Thus the important variables would be the amount of change, the rate of change, the percentage of positive effect derived from the change, the percentage of population affected (for good) by the change and the environment (the environment itself would be made of a lot of other variables).
> 2 votes

# Answer
Like the first answer offered, this is just my opinion. Also accept my apologies if I'm teaching you to suck eggs.

My general approach would be to use Bayesian reasoning. For example:

$$p(A|B) = \frac{p(B|A) p(A)}{p(B)}$$

$A$ could be "IQ between 120 between 130"

$B$ could be "Entered Harvard"

You would need to make many such comparisons and combine them. You could get a probability distribution too. Of course, you need to know, for example, the IQ distribution of people who do enter Harvard. There are many opportunities for subjectivity in such an analysis, such as which variables you consider, and what you do about students who don't reveal their IQs.

A useful way to present the results would be in the form of a computer program or spreadsheet which would allow the reader to apply his own subjective judgements and see the results accordingly. My guess would be about 145, with a strong emphasis on language skills.
> 1 votes

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Tags: measurement, intelligence, iq
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# Question
Title: What is the effect of merely expecting an interruption on performance?
There's a lot of research about how interruptions affect cognitive performance.

* Are there any studies that have looked at the effect of merely expecting to be interrupted (withou being actually interrupted) on performance?
* What does these studies conclude about the effect of merely expecting an interruption on performance?

# Answer
Fortin and Masse (2000) explored the effect of expecting an interruption on the ability to accurately produce a timing interval (e.g., producing a 2000 millisecond timing interval):

From the abstract:

> The interference from nontemporal processing on concurrent time estimation is usually attributed to disruption in timing caused by artentional requirements of nontemporal processing. Here, we examined interruption in timing without concurrent nontemporal processing. Empty breaks of various durations, during time-interval production, lengthened produced intervals. Moreover, an effect of break location was observed: Intervals lengthened proportionally to prebreak duration. When cued and uncued uninterrupted trials were introduced, the lengthening was proportional to the duration for which a break was expected. **It was concluded that attentional time-sharing between time estimation and expectation of its interruption contributed to the interference effect in time-estimation research, independently of any concurrent processing requirements during time estimation.**

So, I suppose you could use this as evidence to support the idea that if an individual is anticipating an interruption, this might consume some attentional resources, especially if he or she is tuned into a signal that might communicate the commencement of the interruption.

### References

* Fortin, C. and Masse, N. (2000). Expecting a break in time estimation: Attentional time-sharing without concurrent processing. Journal of Experimental Psychology: Human Perception and Performance, 26, 1788. PUBLISHER PAGE
> 4 votes

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Tags: cognitive-psychology, io-psychology, performance
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# Question
Title: Do some Photosensitive epileptics desire seizures?
It seems absurd, but from the Wikipedia article on Photosensitive Epilepsy:

> Some PSE patients, especially children, may exhibit an uncontrollable fascination with television images that trigger seizures, to such an extent that it may be necessary to physically keep them away from television sets. Some patients (particularly those with cognitive impairments, although most PSE patients have no such impairments) **self-induce seizures by waving their fingers in front of their eyes in front of bright light or by other means.**

Wikipedia fails to give a citation as to the existence or commonality of this, but it still strikes me as odd.

Have any studies (case studies or preferably experimental results) validated that some PSE patients want or enjoy seizures? Is there some attraction to the causes of these seizures in the patients that causes this behavior?

# Answer
The article I found goes into the general phenomenon of seizure self-induction, but does spend quite a bit of time on photosensitive epilepsy (PSE). It's a review, so there are plenty of references.

It first points out the prevalence of PSE, which occurs in between 2-5% of the population, and approximately 25% of those affected by the disorder are thought to self-stimulate.

The article supports the assertion on Wikipedia that developmentally challenged and "learning disabled" children are most prone to these self-inductive behaviors, but states that children of normal intelligence and higher may have developed strategies to avoid getting caught doing so during recorded sessions. It does not go into much depth regarding adults self-inducing, but tacitly assumes that adults of normal intelligence would be more likely to understand the harm that a seizure could bring them.

There is support for the notion that children with television induced seizures do try to seek out televisions for this self-stimulation behavior, but the article cautions that this compulsive behavior may be associated with the seizure activity itself, and not something the patients are consciously doing, many describe it as "irresistable."

The article lists a handful of reasons that are commonly thought to promote self-induction:

> * Compulsion - whether for pleasure seeking or as a result of seizure activity
> * Willful avoidance of stress or boredom
> * Hedonistic motivation - to experience an "aura"/trance or other pleasurable feelings
> * Sense of control - so they can have a "say" over when their seizures occur, and also so that they can reap the benefits of the refractory period
> * Attention seeking - being the "sick patient" for sympathetic family members
> * Self-treatment - the patient can give themselves a dose of "convulsive therapy" at will, if this gives them therapeutic relief of concomitant disorders

Stronger doses of anticonvulsant medications, medications to quell any pleasurable reinforcement gained from inducing seizures, specialized contact lenses or glasses to block more light (in the case of PSE), and general behavioral modification strategies are all treatment approaches that can be used. Emphasis is given to knowing when children are self-inducing and involving a psychiatrist in the loop of neurological and pediatric care.

> Ng, B-Y (2002) Psychiatric aspects of self-induced epileptic seizures. Australian and New Zealand Journal of Psychiatry,36:534–543.
> 7 votes

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Tags: abnormal-psychology
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# Question
Title: What are the appraisals tendencies for fear and anger?
I understand the actions tendencies for fear and anger. For example: We might verbally insult someone when we are angry. We might feel like running away when we are afraid.

According to appraisal theory, each specific emotion leads us to make assessment or evaluations. So, based on this theory, I don't quite understand what would would be the appraisals for fear and anger?

# Answer
> 5 votes
Examples of appraisals which evoke the emotion of Fear may include dangerous and harmful situations which results people to experience fear. Appraisal of unfair treatment is one cause of Anger which may lead people to behave in an uncertain or unpredictable way both physically and verbally.

# Answer
> 2 votes
By some theories (Carver and Scheier), positive emotions result when you are making progress towards a goal and negative emotions when you are not making progress towards a goal.

They differentiate between approach goals (desired end-states) and avoidance goals (undesired end-states that need to be avoided) and their research has shown that success/failure in approach and avoidance motivations/goals result in different emotions.

To simplify, as per their theory, anger (along with sadness) is associated with lack of progress in an approach motivation task. Fear is associated with lack of progress in escaping or avoiding the threat or undesired end-state. Both Anger and Fear are, in a sense, cognitive appraisals of how far (psychologically /physically) we are from a reward/threat respectively.

I write in detail about this, as well as an alternate model for what Anger and Fear code, in my recent PT blog post .

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Tags: cognitive-psychology, social-psychology, emotion
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# Question
Title: At what age are infants first able to perform pattern recognition?
Chronologically, when is pattern recognition first developed in an infant?

To be considered the first, abilities observed in that instance should prolong throughout the development process. In other words, the instance cannot lapse or be of a temporal nature.

# Answer
This question is difficult to answer if you do not specify what kind of pattern recognition you refer to. In the context of human development, pattern recognition can be as simple as recognizing a row of dots as a line (Gestalt perception) or experiencing the pop-out effect (see Treisman's feature integration theory), but it can also be as complex as face recognition, speech recognition, or reading. Nevertheless, the complexity of a pattern recognition ability does not necessarily correlate with the time of its acquisition. Face recognition, for instance, happens to work pretty early.

There is good evidence (e.g., Pascalis et al 1995) that 4 days old newborns can recognize their mother's face, an ability that definitely requires pattern recognition. Note that this example is a rather conservative estimate: if the newborn is able to detect its mother's face at the forth day, it was able to detect faces probably earlier.

As a more liberal estimate: there are reports of unborn children that respond to certain voices or certain kinds of music already in their mother's womb (for instance being calmed by certain pieces of music). This should definitely require pattern recognition.

**References**

Pascalis O, de Schonen S, Morton J, Deruelle C, Fabre-Grenet M. (1995) Mother's face recognition in neonates: a replication and an extension. Infant Behavior and Development 17:79–85.
> 6 votes

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Tags: perception, developmental-psychology
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# Question
Title: What is the standard way to analyze EEG data in a mismatch negativity paradigm?
I'm running an EEG experiment using a modified auditory mismatch negativity (MMN) design, and I'm wondering if anyone can tell me the best method for data analysis (and recommend any stats programs/packages for this purpose as well).

The experiment will only have a few (6-8) subjects with a high number of trials per subject (~700). The matched condition makes up 75% of the trials. The stimuli are selected from a closed set of 10 items, with an equal frequency of items in the matched/mismatched conditions.

One of the differences between this study and normal auditory MMN tasks is that the expected/unexpected stimuli vary between trials with the expectation set up on a trial-by-trial basis. Therefore, it's possible that the difference in event-related potentials (ERPs) to expected/unexpected stimuli will be averaged out due to small variations in response to these changing stimuli.

Does someone out there know the best EEG data processing and analysis techniques to detect the small ERP in response to auditory MMN stimuli? Can anyone recommend techniques to avoid averaging out small ERPs whose latencies might vary?

# Answer
**Programs/packages for EEG analysis**
There are decent MatLab toolboxes with good tutorials for for the analysis of EEG data. The EEGLAB toolbox (tutorial) can be operated by both GUI and command-line (and script). The fieldtrip toolbox (tutorial) is mainly operated by command line / script.

Of course there are also (commercial) software packages for EEG analysis that do not require Matlab (e.g., BESA, Brain Vision Analyser, eeprobe), but I am not familiar with them.

**Are there techniques to avoid averaging out small ERPs whose latencies might vary?**
No, probably not. ERPs are calculated by averaging across multiple trials because this averaging cancels out all components that jitter in time (that is, mostly noise), i.e. the thing you want to avoid (canceling out of jittering components) is actually the purpose of calculating ERPs.

However, to be sure you should have a look at reviews or tutorials for the measurement of the mismatch negativity. See for instance

Duncan CC, Barry RJ, Connolly JF, Fischer C, Michie PT, Näätänen R, Polich J, Reinvang I, Van Petten C. (2009) Event-related potentials in clinical research: guidelines for eliciting, recording, and quantifying mismatch negativity, P300, and N400. Clin Neurophysiol. 120(11):1883-908. (pubmed)
> 9 votes

# Answer
I use the FieldTrip toolbox in Matlab to analyze my own modified auditory MMN experiment :) But I use MEG, so I don't have that many software options. The toolbox is very powerful but it has a steep learning curve and I would recommend it only if you already have both Matlab and EEG data analysis experience.

I don't analyze my data in the classical MMN way so I can't comment on that. I do hear that the MMN crowd can sometimes be a bit dogmatic in terms of how to approach data analysis, so it's a good idea to get precise information before you sit down to do it. Perhaps contacting someone who has a published MMN study would do the trick.

> One of the differences between this study and normal auditory MMN tasks is that the expected/unexpected stimuli vary between trials with the expectation set up on a trial-by-trial basis. Therefore, it's possible that the difference in event-related potentials (ERPs) to expected/unexpected stimuli will be averaged out due to small variations in response to these changing stimuli.

Since the frequencies of the types of physically different stimuli are identical in the two conditions, this isn't an item of concern. However, there will be more noise in the unexpected condition relative to expected, because of the smaller total number of trials. I'm not sure in what way this can affect the stats (I believe it wouldn't bias them in any systematic way, but I haven't asked an expert - please let me know if you find out!), but generally as a precaution I take a random sample of expected trials, equal to the number of unexpected trials per participant. This way, there is an equal amount of noise in both conditions because you have an equal-sized sample of physically identical stimuli, and the only difference is in stimulus expectation.
> 7 votes

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Tags: methodology, experimental-psychology, statistics, software, eeg
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# Question
Title: The current recommended text for statistics in behavioural sciences
I have an old book: Statistics for the Behavioural Sciences (4th ed.) by Gravetter & Wallnau. I want to transition my textbooks to eBook format, but this book doesn't come like that (as far as I can tell).

The book is comprehensive in explaining each statistical technique using psychological experiments and has exercises for the reader to complete.

I'm afraid I've lost touch with the cutting edge of stats for behavioural sciences, so I don't know what the best book is.

What is the current recommended equivalent text book?

# Answer
> 10 votes
Here's my basic overview of the psychology - statistics textbook market. In general, I think the choice of textbook (where you have a choice) depends on a few factors:

* Applied versus statistical theory (e.g., do you have immediate needs to analyse data)
* Whether and which software package you want to use (e.g., SPSS, R, etc.)
* Which techniques you want learn (e.g., basic bivariate statistics; multivariate stats; etc.)
* How much mathematical rigour you want; if you can handle it, you'll probably get more out of a book pitched at statistics students.

There are also a number of reasonable online options: E.g., hyperstat for similar material as Gravetter and Wallneau.

### Introductory undegraduate textbook

* Statistics for the Behavioral Sciences Gravetter and Wallneau : This remains popular with many students in psychology as an introduction to statistics. It assumes only that you can do very basic algebra. It has lots of pedagogically helpful components. That said, once you move beyond analysing toy datasets for lab reports and so on, you'll want a more advanced and applied book. When it comes to data analysis it focusses on SPSS.
* Discovering Statistics Using SPSS (and now Discovering Statistics Using R): Andy Field does a great job of making statistics fun and accessible. It's also fairly practical in the way that it is grounded in using and interpreting analyses in SPSS (and now R).
* SPSS Survival Manual: This one is more of a cookbook for doing data analysis in SPSS that is suitable for someone analysing their own data in psychology who has only basic training in psychology statistics. It is very applied.
* David C. Howell Statistical Methods for Psychology: This book is substantially more sophisticated than Gravetter and Wallneau however it does provide an overview of many of the basic techniques. However, it goes into a lot more detail about various factorial designs. It also leaves the student with a much more sophisticated understanding.

### Multivariate textbook

* Tabacknick and Fidell Using Multivariate Statistics: This is a well established book in psychology for teaching multivariate statistics (e.g., multiple regression, factor analysis, ANCOVA, MANOVA, and a little bit of SEM). I think it provides a good introduction for typical psychology students. It focusses on interpretation more than mathematics, but there are still some formulas.
* Hair et al Multivariate Data Analysis: This is another popular multivariate book in the social sciences. It is very light when it comes to mathematics and focuses a lot more on interpretation and processes for conducting data analysis. This may either be a good or a bad thing depending on your mathematical background.

# Answer
> 6 votes
Baayen's book, Analyzing Linguistic Data: A practical introduction to Statistics using R is a little more niche than possibly you'd want, but it does offer some coverage of mixed effects modelling, without which I'd be reticent to call any psych stats text "cutting edge".

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Tags: reference-request, statistics
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# Question
Title: Phenomenon that causes music to sound like it's being played at a different tempo than remembered?
Something I've noticed now and then is that I'll be listening to a song off my music player and it sounds like it's being played in a tempo faster or slower than I remember the song being. Is this a defined/known phenomenon, and if so what is it's name and cause/reason for happening?

# Answer
> 10 votes
Vitouch et. al (2006) observed that *"visual tempo significantly influenced the retrieved music tempo."*.

> Music is known to potentially affect the perception of visual scenes (e. g., Vitouch, 2001), as proficiently demonstrated in the movies. But do films also influence the perception of music? This study investigates cross-modal influences in perception, taking influences of “visual tempo” on perceived/retrieved music tempo as a model.

They conclude:

> Both studies demonstrate clear crossover effects: There is not just “musical driving” of film scenes, but also “visual driving” of music perception. Results hint to holistic memory representations of audio-visual material.

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On the other hand, an older paper by Levitin and Cook (1996) observes that long term memory for music *can* preserve the absolute tempo, even by non-trained musicians. They do not investigate the influence of visual stimuli as in the previous paper.

> We report evidence that long term memory retains absolute (accurate) features of perceptual events. Specifically, we show that memory for music seems to preserve the absolute tempo of the musical performance. In Experiment 1, 46 subjects sang popular songs from memory, and their tempos were compared to recorded versions of the songs. Seventy-two of the subjects came within 8% of the actual tempo on two consecutive trials (using different songs), demonstrating accuracy near the perceptual threshold (JND) for tempo. In Experiment 2, a control experiment, we found that folk songs lacking a tempo standard generally have a large variability in tempo; this counters arguments that memory for the tempo of remembered songs is driven by articulatory constraints. The relevance of the current findings to theories of perceptual memory and memory for music are discussed.

<sub> Oliver Vitouch, Sandra Sovdat, Norman Höller (2006) Audio-vision: Visual input drives perceived music tempo. 9th International Conference on Music Perception and Cognition
Levitin, D. J. & Cook, Perry R.(1996) Memory for musical tempo: Additional evidence that auditory memory is absolute. Perception & Psychophysics, 58, pp. 927-935. </sub>

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Tags: terminology, memory, perception, music
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# Question
Title: Do fetuses exhibit pattern recognition in utero?
I've heard that fetuses exhibit "likes", such as preferring sweeter amniotic fluid or the sound of their mother's voice. To show preference for specific voices as opposed to inborn stimuli like sweet, some form of pattern recognition would have to be involved.

By pattern recognition I simply mean exhibiting any sort of indication that by repeated exposure to a stimulus the fetus' response changes, showing that it in some way has identified the stimulus as being previously experienced.

I know of some research that indicates newborns recognize and prefer their own mother's voice but I'm not aware of specific research on children in utero.

Does any research indicate that fetuses show pattern recognition in utero, such as voice recognition? Is there an approximate time this ability presents itself?

# Answer
> 7 votes
The preference for mother's voice over a stranger's voice has been show in utero by Kisilevsky et al. (2003) by measuring the fetus' heart rate. It increased in response to mother's voice and decreased in response to a stranger's voice compared to baseline. Kisilevsky and Hains (2011) followed up the earlier study, and determined that the onset of recognition occurred at 32–34 weeks GA. Thus, at least for vocal stimuli, there is definitely some recognition from the infants. My only issue with these studies is that the mothers could hear the stimuli, thus there could be interaction from a hormonal response of the mother to her own voice and the fetus picking up on that instead of the actual auditory input.

An even more liberal reading of "recognition" as defined by the OP is possible. If we follow in the footsteps of Maturana and Varela then we should talk about the brain/mind responding not to external stimuli but to its own internal sensory world. In that case, we can consider adaptation even before sensory organs are fully developed or functional. In that case the fetus starts to adapt to senses-to-be before they develop.

Penn & Shatz (1999) showed that the connections from the eye to the visual cortex form before the retina is developed enough to respond to light. At this time the retinal ganglion cells spontaneously generate highly correlated bursts of action potentials similar to the sort of data they will generate once they actual start sensing. The preliminary bursts allow the human fetus to start developing its visual cortex before it even has functional retina. Thus, the brain of the fetus starts to learn and recognize patterns before it even has proper external sensory input.

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Tags: developmental-psychology, recognition
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# Question
Title: What does "veridicality" mean in terms of psychology?
I'm reading the paper "Visual Space Perception and Visually Directed Action" by Loomis, Da Silva, Fujita and Fukusima (1992; pdf). In this paper, the word 'veridicality' is used in several sentences.

Some examples:

> * Even with such a narrowed focus, it is apparent that no consensus on the veridicality of visual space perception exists, for the experimental results depend strongly on both the criterion of veridicality and the psychophysical method used.
> * One criterion for veridicality is linearity of the function relating perceived egocentric distance to physical distance.

I used dictionaries and websites (including Wikipedia) to get a grasp of this concept, however, I found nothing that gave good meaning to this word. I assume this is a psychological term, since the linguistic meaning didn't fit well in my opinion.

**What does 'veridicality' mean, and how I should interpret it in this context?**

**References**
Loomis JM, da Silva JA, Fujita N, Fukusima SS. (1992) Visual space perception and visually directed action. Journal of experimental psychology: Human perception and performance 18(4), 906-921.

# Answer
Veridicality is a term used in cognitive science; it is the degree to which your internal representation of the world accurately reflects the external world.

### Some background

Since the work on Humberto Maturana in color perception, it was considered very important to not always focus on the fact that there is some external stimuli to be cognized by the subject and then reacted on, but that instead there is an internal world or representation which is then cognized and responded to. In many cases the veridicality of the internal representation is very good, and the experimenter can focus on just the easy-to-observe external stimuli. However, in many settings (like color perception) the veridicality of the internal representation is low (easiest way to imagine this: think of a difference in internal representation between a color-blind and non-color-blind person). Hence the experimenter needs to explicitly measure the internal representation and try to understand how it acts. Once you have a measure of this (a 'criterion for veridicality') then you can start to think about how the subject cognizes the stimuli.

### Specific to this paper

In the context of the first sentence, what the authors are saying is: even with the narrow focus, it appears that the accuracy of the internal representation does not improve. Thus, the experimental results depend not only on the external stimuli (psychophysical method used) but how good we are at estimating the accuracy of the internal representation (criterion of veridicality).

In the second sentence they propose a metric of veridicality: ask how far you think an object is (say in meters) if the results scale linearly with actual distance, then the internal representation of space is good, else it is not.
> 11 votes

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Tags: terminology, perception, experimental-psychology
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# Question
Title: Do high heels increase female attractiveness in men only through indirect means?
It seems widely accepted that, overall, men tend to find women in high heels more attractive. (There will, of course, be many exceptions to this rule.)

> "High heels may well be the most potent aphrodisiac ever concocted." -- Rossi 1981

However, the increase in attraction seems to be only indirectly ascribed with wearing high heels. Typically this is described along the lines: high heels cause a change in the posture of the female, which the male finds (sexually) attractive.

> Question: How can we exclude the possibility that the high heels themselves are not the main cause of the increase in attractiveness?

That is, how can we exclude the possibility that men, overall, primarily just like the sight of women in high heels, for some reason or another?

My thoughts:

* If the increase in attractiveness were primarily due to these indirect factors, then we should see a comparable increase in attractiveness e.g. if a woman were merely to stand on a slope. (Although, this would not account for the addition factors, such as gait, and the sound made when walking in high heels.)
* There are things that women do, such as fingernail painting, which increases attractiveness, but (arguably) not sexual attractiveness. It seems plausible that the "femininity" associated with wearing high heels (as with fingernail painting) could be a large factor in the increase in attractiveness.

**References**
Rossi WA. (1981) High heels: the agony and the extasy. Journal of the American Podiatry Association 71(12), 698-699.

# Answer
> 8 votes
It is probably quite simple to test whether high heels themselves are the main cause of the increase in attractiveness, or rather the changes to posture imposed by them - just let participants rate the attractiveness of women who do not wear high-heels, but, for instance, hold them in their hand.

Alternatively, you could expose one half of your participants to high heels and the other half not. Afterwards let them rate pictures of women and compare the mean ratings of the groups.

In principle, you could a multitude of experiments with women and high heels - as long as the women do not wear the high heels, you can exclude that the effect on posture explains your results.

An alternative approach, suggested by Artem Kaznatcheev in the comments, would be to compare the attractiveness ratings on women with and without high heels while their feet are not visible (e.g., covered or removed from the picture). Finding the same rating difference like observed with visible feet would suggest an effect of posture caused by high heels, rather than high heels themselves. (Actually you would need at least an two-by-two design (\[high-heel vs. no-high-heel\] x \[feet-visble vs. feet-invisble\]) to draw this conclusion.)

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Tags: physical-attraction
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# Question
Title: Is there a field of research based around music and emotion in the brain?
I'm looking for research surrounding the scientific study of music and emotion and its effects on the brain. In particular, are there known parts of the brain which activate when playing or listening to music?

Is there a specific field of study based around music and cognitive science?

# Answer
Well it depends what you mean by "field of study", but yes there is significant Cognitive Science research on Music and emotional arousal and/or brain activity. In particular **Cognitive Neuroscience** is most relevant to actually mapping brain activations involved with various forms of music appreciation and creation.

A good study specifically on music and emotion is Investigating Emotion With Music: An fMRI Study by Stefan Koelsch et all. They investigate *listening* to music and have nice heatmaps of brain activity during listening. There's many other papers exploring the activity pattern when listening or creating music, but the conclusion of this article sums up some of the major areas:

> In the present study, activations during the perception of unpleasant music were observed within an extensive neuronal network of limbic and paralimbic structures comprising the **amygdala, hippocampus, parahippocampal gyrus, and temporal poles**. Although clear increases of BOLD signals were observed in those structures in response to unpleasant music, strong signal decreases were also measured in response to pleasant music. This indicates that these structures respond to both pleasant and unpleasant auditory information with emotional valence, and that listening to music has the capacity to up- as well as down-regulate neuronal activity in these structures.
>
> ...
>
> During the presentation of the pleasant music, activations were observed in the ventral striatum, the **anterior superior insula, and in the Rolandic operculum**.

So interestingly, music with different emotional context results in different patterns and locations of brain activation. The full article has more specific information, and you can feel free to ask about more specific patterns of activation in regards to more specific stimuli.
> 7 votes

# Answer
This answer is meant to add more information in addition to the one above. Also, I have not seen the original comment thread, and apologize in advance if I have given redundant information.

**Fields that look at music and the brain**

Researchers in many fields have an interest in understand how music is processed by the brain and more particularly how emotion ties in. These can include:

* (auditory) cognitive neuroscience
* (music) psychology and psychoacoustics
* music therapy
* music technology (perhaps look into Music Information Retrieval, as work on emotional/mood classification is growing)

etc.

Different fields may focus on different aspects and may use different methods and techniques, but can also have overlaps. Wikipedia has a brief article on music cognition as an umbrella term/field.

**Areas involved with music performance and perception**

The actual focus of music cognition research can be further divided (as you have in your question), into research on music performance, music perception, or interactions with each other and other modalities, to name a few.To answer your first question, music performance will inherently rely on basic motor networks and often looks at the brains of musicians compared to amateurs or non-musicians. Music perception relies on auditory circuits at a lower level. As language cognition also involves the auditory system, studies often look what/where the differences occur. You can typically find chapters about the motor or auditory system in textbooks. In addition, there are other higher level processes and their associated areas that may be involved (planning, memory, classification, recognition etc.). If you are further interested, here is one review on a few recent developments in music performance (Thompson et al., 2006)\[pdf\]. Here is another that covers recent work on the perceptual side (Koelsch & Siebel, 2005).

**Music and Emotion**

To add to the above answer and provide you with more references, Chapter 5 of (Hunter & Schellenberg, 2010) provides an overview of the studies that show how music elicits emotional responses. Interestingly, there is evidence that the emotional response to music is separate pathway than non-emotional judgement of music. This was seen in a patient, who after brain damage had significant impairments in non-emotional music tasks (recognizing melodies, sing more than one pitch, etc.) but intact emotional processing of music (Peretz et al., 1997).
> 6 votes

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Tags: emotion, music
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# Question
Title: How do people that can't perceive 3D view a stereoscopic 3D image or movie?
According to Mendiburu (2009), 3-15% of the people can't view a stereoscopic 3D image or movie, mostly due to poor binocular vision.

Imagine one of those is in the movie theater, trying to watch a 3D movie. How would this movie appear to this person?

<sub> Mendiburu (2009) 3D Movie making: stereoscopic digital cinema from script to screen, Oxford, England: Focal Press) (Free PDF) </sub>

# Answer
> 9 votes
People who are unable to perceive stereoscopic depth typically only perceive information from the dominant eye.

Failure to perceive stereoscopic depth is usually caused by conditions where the eyes do not converge properly (e.g., strabismus). If left untreated, it is not possible to develop the necessary correspondance between the two signals from either eye, and one eye will dominate over the other. The result is that the majority of visual cortical neurons will respond to stimuli presented to the dominant eye, whereas there will be far fewer binocular neurons (i.e., neurons that respond to stimuli from either eye) and monocular neurons that respond to stimuli from the weaker eye.

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Tags: perception, vision
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# Question
Title: Does the fusiform face area in patients with Prosopagnosia (face blindness) show lower activity under an fMRI?
I watched last night's episode of 60 minutes (and part 2) about Prosopagnosia (Face Blindness) and found it absolutely fascinating. They mentioned in the segment (Around 5:22 into the second part of the online video) that Nancy Kanwisher of MIT has studied the MRI scans of people without Prosopagnosia and found that the fusiform face area lit up on an MRI when an individual was shown an image of a face.

Nancy Kanwisher then goes on to state the following:

> I really did not expect to see a fusiform face area \[on an MRI scan of a patient with Prosopagnosia\]. \[...\] And we looked at the data and his face area was beautiful, it was textbook. \[...\] It tells us that the problem is not that this thing \[(the fusiform face area)\] does not exist, there it is!

The image shows an MRI scan of a patient who has Prosopagnosia, demonstrating that the patient does have a fusiform face area. However, **it was unclear to me whether the fusiform face area of an individual suffering from Prosopagnosia is *less active* when presented with a face than that of an individual without Prosopagnosia**.

What did Nancy Kanwisher find with regards to that? Does the fusiform face area in individuals with Prosopagnosia exist but remains dormant? Or is it just as active but for some other (probably unknown) reason simply fail to relay the proper information to the rest of the brain?

# Answer
> 12 votes
It is not widely thought that impaired function or destruction of the fusiform is sufficient to produce prosoganosia. It is currently widely held that face processing involves a network of regions in the occipital and temporal lobes (e.g., the occipital face area, posterior superior temporal sulus, anterior superior temporal sulus, anterior collateral sulcus). For example, Bruno Rossion reports a patient with prosopagnoisa who has widespread damage to bilateral occipital and temporal brain regions but with a spared right FFA. Moreover, work by Marlene Behrmann has shown that people with developmental prosopagnosia have disrupted connections between the posterior temporal lobes (ie near the FFA) and the anterior temporal lobes. This is significant because there is growing evidence that there may be face selective regions in the anterior temporal lobes and that they are more directly involved in face recognition. Moreover there is some evidence that this anterior temporal region modulates the activity in the FFA (Nestor, Plaut, Behrmann, 2011 PNAS). So it might very well be that the FFA does show decreased activity in a face recognition task, but this might be due to impaired feedback to this region. On this view, lower activity in FFA is the effect of prosopagnosia not the cause, so making comparisons on levels of activity within one region might not be as meaningful as you think.

### References

* Nestor, A., Plaut, D.C., & Behrmann, M. (2011). Unraveling the distributed neural code of facial identity through spatiotemporal pattern analysis. *Proceedings of the National Academy of Sciences, 108*, 9998. LINK

# Answer
> 5 votes
Yes, though not necessarily in the way that you are meaning - some prosopagnosics will have damage to the area in question, so you could say the activity is lower because there is not much left of it!

Quick google reveals this paper: http://cercor.oxfordjournals.org/content/20/8/1878.abstract

It's recent so will probably review the evidence you are interested in.

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Tags: perception, neuroimaging, neurology, brain-injury
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# Question
Title: Are there any journal articles in psychology that have promoted and discussed reproducible data analysis?
I consider reproducible analysis to be really important. In particular, I'd like to see more researchers in psychology:

* sharing their data
* producing their journal articles using literate programming technologies like Sweave and knitr that combine data analysis code and text into an integrated documenst.

I consider this particularly important in light of concerns over research fraud (e.g., data fabrication) and various forms of data fishing (e.g., testing many hypotheses and only reporting the significant one).

Certainly in statistical fields, there is a lot of discussion about the importance of reproducible analyses (e.g., see here, and here). However, I sometimes feel that in psychology this is only starting to filter through.

Thus, my question is:

* **Are there any journal articles in psychology that have advocated reproducible analysis?**

There are many angles that such articles might take: reward structures that discourage open science and reproducible analysis; technical challenges which make it difficult to do such analyses; how-to articles that outline how to perform reproducible analyses in psychology. I'd be interested in any articles that address these topics.

# Answer
It's not a journal article, but it's a project, called Reproducibility Project. They are re-doing psychological studies to estimate the reproducibility of a sample of studies. They try to stay as close as possible on the original study (they e-mail the author(s) for the exact stimuli etc.). Here's the main site and here's the link to their spreadsheet.

This is a short article promoting the sharing of data in psychology. Another related study (by the same author) is also mentioned.
> 9 votes

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Tags: reference-request, statistics, reproducible-research
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# Question
Title: How do you refer to something in APA-style that is not submitted to be published?
I'm writing a paper in APA-style. At the end of it, I have my references. There is this one paper (actually an internship report) that I refer to, but it hasn't been submitted for publication. How should I write this down?

# Answer
Usually citations of gray literature should be avoided. If, however, it is necessary, the APA suggests to provide as much information as possible (see, for instance, the APA style blog). For specific style suggestions, see, for instance, a library handout summarizing the APA guides on gray literature.
> 6 votes

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Tags: publication-process, apa-style
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# Question
Title: Perceptual flicker when rotating my face
### Informal Experiment:

1. I look up at a wooden beam on the ceiling, or I look at the office door; both the door and the ceiling are about 2 meters from my face.
2. I rotate my face 90 degrees left or right at a rate of about 90 degrees per second. (You may have to adjust this rate to experience the flicker. Too fast or too slow, and you won't experience the flicker.)

### Results:

* My visual perception (of the edge of the door or ceiling) flickers rather than being smooth and continuous.
* I typically perceive 4 (but sometimes 5 or 6) images during the rotation, which translates to 1/3 second between images or one image per 30 degrees of rotation.

### Notes:

* Ensure that ambient illumination doesn't flicker. Sunlight is suitable. Most electrical light that runs on AC is not.
* I understand that not everyone who tries this experiment will experience this phenomenon.
* This phenomenon also occurs when viewing a sheet of paper held at arm's length and pressed against a contrasting wall (e.g., white paper on brown wall). Rotating the paper instead of your face does not generate the phenomenon.
* The intention of the linked YouTube video is only to show which plane to rotate.
* I recorded a video of my face during the experiment. Reviewing the video, I see no eye movement.

### Question:

Is there any research on this phenomenon? (I have been unable to find anything on it, perhaps because I don't know the proper terminology.)

# Answer
> 4 votes
I'm guessing that you are experiencing the interplay of two mechanisms: When you start to turn your head, the "vestibulo-ocular reflex" tries to hold the visual scene steady by counteracting your head movement. But as you continue to turn your head (apparently at about 30 deg. intervals), a "saccade" kicks in to restore your gaze to a point straight in front of your face.

A similar effect can be observed when the visual scene moves, as when you look out a train window, but in this case, rather than the vestibulo-ocular reflex, it would be "smooth pursuit eye movement" that tries to hold the visual scene steady. (Wikipedia has good articles for all three of the quoted terms.)

An interesting way to check this hypothesis would be to videotape your face as you perform the experiment and observe your eye movements in the video. I'm looking forward to a YouTube posting...

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Tags: cognitive-modeling, vision
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