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The Role of Interface Style in Planning during Problem Solving

The Role of Interface Style in Planning during Problem Solving Christof van Nimwegen (christof@cs.uu.nl) Herre van Oostendorp (herre@cs.uu.nl) Hermina Tabachneck-Schijf (h.schijf@cs.uu.nl) Center for Content and Knowledge Engineering, Utrecht University Padualaan 14, De Uithof, 3584CH, Utrecht, The Netherlands Abstract It is argued that support from an interface during problem solv- ing can make interaction easier. Interfaces often display rele- vant information, making recall unnecessary and relieving working memory, called externalization. However, externaliz- ing information might not necessarily instigate planning, under- standing and knowledge acquisition from the user. In previous studies, the effects of externalizing information in an interface not always converged. We describe an experiment investigating the influences of (1) inducement to plan and (2) externalizing information on problem solving. Contrary to others’ findings, no advantages of externalization were found. Instead, NOT ex- ternalizing (requiring internalization) yielded advantages and facilitated planning from the user. Keywords: Interface; knowledge acquisition; screen represen- tation; planning; problem solving; externalization Introduction Many cognitive tasks are computer-based nowadays. We explore multimedia environments, and use computers in edu- cation, entertainment, office tasks and many other domains. Computer interfaces are often complex, and applications can have hundreds of functions. Designing the right computer interface for the right task can be tricky and this gave rise to a whole domain of human computer interaction research. “Us- ability” became a buzzword. One notion that came from us- ability studies is the importance of “minimizing user memory load“, and a common recommendation is that users should interact on basis of recognition rather than recall. In practice this means that information, e.g., text, objects, actions and options should be made available only when a user could need them for a task, while hiding non-relevant information: externalization of information. By externalization we mean providing relevant information on the interface, making recall of certain knowledge unnecessary, thus relieving working memory. On the contrary, when information is not external- ized, certain task information is less directly available and needs to be internalized, i.e. inferred and stored in memory before it can be used. If this occurs, an already constructed plan is available for subsequent use. There are many different types of information that can be externalized. As examples, think of interfaces that “take the user by the hand” by limiting choices and providing feedback (e.g. Van Oostendorp & De Mul, 1999), such as greying-out menu items that cannot be used in a particular context, thus offering a context-sensitive interface with just “possible” actions. This type of externali- zation prevents errors and limits search. For example in Word, one cannot select “paste” from the “edit”-menu, when nothing is copied or cut first. “Paste” is shown in grey, indi- cating that the command exists, but you cannot now use it. Wizards externalize the solution path. Help-options external- ize the fact that extra information on a topic is available. That externalization is considered helpful is reflected in various GUI-guidelines, e.g., “visibility status”, “feedback”, “grey out inapplicable items”, “provide help-functions”. But is externalization always helpful? When looking more specifically at certain problem solving tasks, planning and learning are thought to be essential factors. One could argue that during computer-based problem solving, externalizing all information can lead to “experiential cognition” (Norman, 1993): users are not triggered to look for underlying rules, form plans, or learn. In contrast, externalizing less informa- tion may trigger a user to engage in “reflective cognition”, i.e. to plan and learn more actively. This paper focuses mainly on the users’ behavior that two interface styles (externalization and internalization) provoke, and specifically on the amount of planning and reasoning from the user’s side. In literature, traditionally the role of external representa- tions has been underestimated. The pioneering work of Gib- son (1979) has stimulated better analysis of the interaction between internal and external representations. Norman (1988) proposed the idea that knowledge might be as much in the world as it is in the head. He pointed out that the information embedded in technological artifacts (such as interfaces) was as important to task achievement as the knowledge residing in the mind of the individual who used that artifact. Norman argued that well-designed artifacts that externalized informa- tion as to their functions could reduce users’ memory load, while badly designed artifacts increased the knowledge de- mands made on the user. The message stemming from this distinction drew attention to the implications that design deci- sions could have. Larkin (1989), for instance, considered the role played by differences in external displays in cognitive problem-solving, finding that externalizing information, ena- bling ‘display based problem solving’, helped people recover from interruptions in work. Note that Larkin’s most revealing display externalized all the pieces of the solution path that had been accomplished, enabling a quick pick-up after a within- trial interruption. Tabachneck-Schijf, Leonardo and Simon (1997) created a model in which small individual pieces from different representations were linked on a sequential and tem- porary basis to form a reasoning and inferencing chain, using visually encoded information recalled to the Mind's Eye from