Wason selection task
The Wason selection task (or four-card problem) is a logic puzzle devised by Peter Cathcart Wason in 1966. It is one of the most famous tasks in the study of deductive reasoning. 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. The original task dealt with numbers (even, odd) and letters (vowels, consonants).
The importance of the experiment is not in justifying one answer of the ambiguous problem, but in demonstrating the inconsistency of applying the logical rules by the people when the problem is set in two different contexts but with very similar connection between the facts.
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 
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.
This latter comment is also controversial, since it does not explain whether the subjects regarded their previous solution incorrect, or whether they regarded the problem sufficiently vague to have two interpretations.
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.
Evolutionary psychologists Leda Cosmides and John Tooby (1992) 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 different 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. Cosmides and Tooby argued that 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.
According to Cosmides and Tooby, 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. They argued that such a distinction, if empirically borne out, would support the contention of evolutionary psychologists that human reasoning is governed by context-sensitive mechanisms that have evolved, through natural selection, to solve specific problems of social interaction, rather than context-free, general-purpose mechanisms. In this case, the module is described as a specialized cheater-detection module.
Davies et al. (1995) have argued that Cosmides and Tooby's argument in favor of context-sensitive, domain-specific reasoning mechanisms as opposed to general-purpose reasoning mechanisms is theoretically incoherent and inferentially unjustified. Cosmides and Tooby have adapted the Wason selection task to test for one aspect of propositional logic while ignoring general-purpose reasoning based on syllogistic logic, predicate logic, modal logic, and inductive logic. They assumed that the domain-specific hypothesis was correct without first ruling out the general-purpose hypothesis. Moreover, the experiments intended to show that reasoning is not governed by general-purpose rules either fail to eliminate the general-purpose hypothesis or else actually provide evidence supporting it, which according to Davies and his colleagues suggests that the argument in favor of domain-specific reasoning might be empirically false. In addition to that, Cosmides and Tooby assume that reasoning is either determined exclusively by domain-specific or general-purpose algorithms, a dichotomy that Davies et al. view as misconceived.
An alternative explanation is 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 
- Wason, P. C. (1966). "Reasoning". In Foss, B. M. New horizons in psychology. Harmondsworth: Penguin.
- Wason, P. C.; Shapiro, Diana (1971). "Natural and contrived experience in a reasoning problem". Quarterly Journal of Experimental Psychology 23: 63–71. doi:10.1080/00335557143000068.
- "The Wason selection task has often been claimed to be the single most investigated experimental paradigm in the psychology of reasoning". Ken Manktelow (1999). Reasoning and Thinking, Hove: Psychology Press, p. 8
- Wason, P. C. (1977). "Self-contradictions". In Johnson-Laird, P. N.; Wason, P. C. Thinking: Readings in cognitive science. Cambridge: Cambridge University Press. ISBN 0521217563.
- J.St.B.T. Evans et al. (1993). "Human reasoning: The psychology of deduction." Hove: Lawrence Erlbaum Associates.
- Oaksford, M.; Chater, N. (1994). "A rational analysis of the selection task as optimal data selection". Psychological Review 101 (4): 608–631. doi:10.1037/0033-295X.101.4.608.
- Stenning, K.; van Lambalgen, M. (2004). "A little logic goes a long way: basing experiment on semantic theory in the cognitive science of conditional reasoning". Cognitive Science 28 (4): 481–530. doi:10.1016/j.cogsci.2004.02.002.
- van Benthem, Johan (2008). "Logic and reasoning: do the facts matter?". Studia Logica 88 (1): 67–84. doi:10.1007/s11225-008-9101-1.
- Cosmides, L.; Tooby, J. (1992). In Barkow et al.. Cognitive Adaptions for Social Exchange. New York: Oxford University Press. 
- Davies, Paul Sheldon; Fetzer, James H.; Foster, Thomas R. (1995). "Logical reasoning and domain specificity". Biology and Philosophy 10 (1): 1–37. doi:10.1007/BF00851985.
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.
- 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