{'fraction_non_alphanumeric': 0.03312268468075834, 'fraction_numerical': 0.012856831553715406, 'mean_word_length': 5.270491803278689, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 4, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 4, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Money Illusion in the human brain

Money Illusion in the human brain Krishna P. Miyapuram (krishna.miyapuram@unilever.com) Department of Physiology, Development and Neuroscience, University of Cambridge, CB2 3DY, U.K. Unilever R & D, 120, Olivier van Noortlan, Vlaardingen, 3133 AT, The Netherlands Philippe N. Tobler (pnt21@cam.ac.uk) Department of Physiology, Development and Neuroscience, University of Cambridge, U.K. Lucy Gregorios-Pippas (lucygregpip@hotmail.com) Department of Physiology, Development and Neuroscience, University of Cambridge, U.K. Wolfram Schultz (ws234@cam.ac.uk) Department of Physiology, Development and Neuroscience, University of Cambridge, U.K. Abstract Monetary rewards are uniquely human. Most fMRI studies use monetary rewards due to the ease of presenting them visually. We tested the efficacy of different forms of monetary reward presentations -- alphanumeric display, pictures of coins (pence) and money bills. For alphanumeric and coin presentation, subjects received exactly the same amount that was displayed whereas for money bills, the amount received was equal to 1% of the amount displayed. Money illusion is said to occur when participants’ responses are driven by the nominal rather than the real value. The total money accumulated was displayed throughout the experiment at bottom of the screen. Money illusion related responses were observed in lateral orbitofrontal cortex. Interestingly visual saliency of displayed monetary rewards activated the medial orbitofrontal cortex. It is expected that higher subjective reward value can be achieved by the money illusion technique. gambles in experimental situations. Holt and Laury (2002) found that in a lottery-choice experiment, the behaviour of participants was largely unaffected by scaling up the hypothetical rewards. Their results are contrary to Kahneman and Tversky, suggesting that people cannot imagine how they would actually behave in high-incentive conditions. Johnson and Bickel (2002) found no difference in delay-discounting for real and hypothetical rewards. Using an Iowa gambling task, Bowman and Turnbull (2003) did not find any difference between real and facsimile (real values x 1000) reinforcers. However, Fernie and Tunney (2006) report that the performance was affected by reinforcer type (real or fascimile) when there was no hint about the nature of decks. With inclusion of the hint, they did not observe these differences. Keywords: reward; orbitofrontal cortex; money illusion; fMRI; hypothetical rewards; monetary incentives; saliency. Introduction The importance of money in everyday life makes it a strong reinforcer. The incentives offered in economics experiments are far smaller than real life. Gneezy and Rustichini (2000) suggest that monetary incentives at low value can have a detrimental effect on performance. The effect on monetary compensation on performance was not monotonic. While larger amount of money yielded higher performance, smaller amounts yielded poorer performance than those offered no compensation. Typical fMRI studies involve hundreds of trials with each trial lasting around 10 seconds. It has been shown that subjects work harder, more persistently, and more effectively, if they earn more money for better performance (Camerer & Hogarth, 1999). Due to experimental constraints, monetary rewards are visually presented to the subject, as they cannot be delivered inside the fMRI scanner. Hence, the intrinsically arousing properties of money are typically diminished due to the visual presentation (Zink et al., 2004). Kahneman and Tversky (1979) suggest that hypothetical choices can be used to overcome the limitation of small Figure -1: Money illusion cartoon (A) The more natural 3-dimensional view being perceived creating a visual illusion that the farther coin is bigger in physical size. (B) Money illusion occurs when the nominal values of displayed rewards reinforce rather than real rewards. In this paper, we use a technique called money illusion in which subjects are shown large amount of money, but they have been informed that they would be able to take home only a specific percentage of the displayed money. A previous study (Dreher et al., 2006) has used similar strategy but not explicitly studied the effect of using hypothetical rewards. In economics, money illusion refers to the bias in assessment of the real value of an economic transaction, induced by nominal evaluation. We often think in terms of nominal values. However, it is known from the framing effect that the same situation can be perceived