“It is trivially easy to affirm that the reasoning in this example is valid, that is to say that the conclusion must be true if the premises are true. But other examples are not so obvious. People are particularly prone to make the error known as affirmation of the consequent, illustrated by the following example:

• If the government is engaged in a cover-up of the existence of UFOs then they will deny that UFO landings have taken place.
• The government does deny that UFO landings have taken place.
• Therefore the government is engaged in a cover-up of the existence of UFOs.

People often erroneously judge that syllogisms such as that presented above are valid. The error made here is based upon interpreting the “if” to mean “if and only if”. Although the government would indeed deny that UFO landings were taking place if they were engaged in a conspiracy to conceal the existence of UFOs, there are alternative reasons why they might deny that UFO landings have taken place, the most obvious being that no such landings have in fact occurred…

…in summary, it appears that the correlation between paranormal belief and a deficit in syllogistic reasoning is fairly robust, with only two published failed attempts to date to find such an effect (one from a believer, one from a sceptic). Irwin’s interesting hypothesis regarding the possible effects of context has fared less well in empirical tests.

French, C. C., & Wilson, K. (2007) Cognitive factors underlying paranormal beliefs and experiences. In S. Della Sala (ed.). Tall Tales About the Mind and Brain: Separating Fact From Fiction. Oxford: Oxford University Press. Chapter 1, pp. 3-22.