Wason selection task

Which card(s) must be turned over to test the idea that if a card shows an even number on one face, then its opposite face is red?

Devised in 1966 by Peter Cathcart Wason, the Wason selection task, one of the most famous tasks in the psychology of reasoning, is a logic puzzle which most people get wrong. An example of the puzzle is:

You are shown a set of four cards placed on a table, each of which has a number on one side and a colored patch on the other side. The visible faces of the cards show 3, 8, red and brown. Which card(s) must you turn over in order to test the truth of the proposition that if a card shows an even number on one face, then its opposite face is red?

A response that identifies a card that need not be inverted, or that fails to identify a card that needs to be inverted, is incorrect. Note that the original task dealt with numbers (even, odd) and letters (vowels, consonants).

Evolutionary psychologists have gathered experimental evidence that people find the Wason task much easier if it is placed in the context of a social rule that the experimental subject is asked to police, suggesting that humans solve the social-rule problem with a specialized mental module that evolved to catch cheaters in a social environment.

Solution

The correct response was to turn the cards showing 8 and brown, but no other card. Remember how the proposition was stated: "If the card shows an even number on one face, then its opposite face is red." Only a card which has an even number on one face and which is not red on the other face can invalidate this rule. If we turn over the card labeled "3" and find that it is red, this does not invalidate the rule. Likewise, if we turn over the red card and find that it has the label "3", this also does not break the rule. On the other hand, if the brown card has the label "4", this invalidates the rule: it has an even number, but is not red. The interpretation of "if" here is that of the material conditional in classical logic.

Explanations of performance on the task

In Wason's study, not even 10% of subjects found the correct solution. This result was replicated in 1993.

Some authors have argued that participants do not read "if... then..." as the material conditional, since the natural language conditional is not the material conditional. (See also the paradoxes of the material conditional for more information.) However one interesting feature of the task is how participants react when the classical logic solution is explained:

A psychologist, not very well disposed toward logic, once confessed to me that despite all problems in short-term inferences like the Wason Card Task, there was also the undeniable fact that he had never met an experimental subject who did not understand the logical solution when it was explained to him, and then agreed that it was correct.

Policing social rules

As of 1983, experimenters had identified that success on the Wason selection task was highly content-dependent, but there was no theoretical explanation for which content elicited mostly correct responses and which ones elicited mostly incorrect responses.

Leda Cosmides and John Tooby identified that the selection task tends to produce the "correct" response when presented in a context of social relations. For example, if the rule used is "If you are drinking alcohol then you must be over 18", and the cards have an age on one side and beverage on the other, e.g., "16", "drinking beer", "25", "drinking coke", most people have no difficulty in selecting the correct cards ("16" and "beer"). In a series of experiments in a large number of contexts, subjects demonstrated consistent superior performance when asked to police a social rule involving a benefit that was only legitimately available to someone who had qualified for that benefit. Experimenters have ruled out alternative explanations, such as that people learn the rules of social exchange through practice and find it easier to apply these familiar rules than less-familiar rules.

This experimental evidence supports the hypothesis that a Wason task proves to be easier if the rule to be tested is one of social exchange (in order to receive benefit X you need to fulfill condition Y) and the subject is asked to police the rule, but is more difficult otherwise. Such a distinction, if empirically borne out, would support the contention of evolutionary psychologists that certain features of human psychology may be mechanisms that have evolved, through natural selection, to solve specific problems of social interaction, rather than expressions of general intelligence. In this case, the module is described as a specialized cheater-detection module. Alternatively, it could just mean that there are some linguistic contexts in which people tend to interpret "if" as a material conditional, and other linguistic contexts in which its most common vernacular meaning is different.

See also

• Cognition
• Confirmation bias
• Evolutionary psychology
• Logic
• Necessary and sufficient conditions
• Psychology of reasoning
• Reasoning

Further reading

• Barkow, Jerome H.; Leda Cosmides, John Tooby (1995). The adapted mind: evolutionary psychology and the generation of culture. Oxford University Press US. pp. 181–184. ISBN 978-0-19-510107-2. 

External links

• Here is the general structure of a Wason selection task — from the Center for Evolutionary Psychology at the University of California, Santa Barbara
• CogLab: Wason Selection — from Wadsworth CogLab 2.0 Cognitive Psychology Online Laboratory
• Elementary My Dear Wason - interactive version of Wason Selection Task at PhilosophyExperiments.Com