Wason test

Named in honour of Peter Cathcart Wason, a Wason Test is a logical puzzle which is formally equivalent to the following question:

An investigator is shown a set of four cards placed on a table each of which has a number on one side and a coloured patch on the other side. The visible faces of the cards show 3, 8, red and brown. Which cards should the investigator turn over in order to test the truth of the proposition that if a card shows an even number, then its opposite face shows a primary colour?

A response which identifies a card which need not be inverted, or a response which fails to identify a card which needs to be inverted are both incorrect. The correct response is that the cards showing 8 and brown must be inverted, but no other card.

Experiments have shown that, presented with a Wason test as an uncontextualised logic puzzle, people perform very poorly. Furthermore, even of those who respond correctly, some obtain the correct result by conscious application of the contrapositive rule. By contrast, some (though not all) Wason tests prove much easier when they are presented in a context of social relations.

Adherents of evolutionary psychology have argued that a simple rule distinguishes Wason tests which people find easy from those that they find difficult. The suggested rule is that a Wason test proves to be easy if the rule to be tested is one of social exchange (in order to receive benefit X you fulfill condition Y) and the subject is asked to police the rule, but is difficult otherwise. If this classification is accepted, then it supports 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.

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