Slow reasoning can result in errors too

By now you will have probably realised that the representativeness bias has also been held responsible for the conjunction fallacy – remember Shelia our bank teller?

According to some theorists, the reason why people are seduced into making the conjunction error is because the brief description of our bank teller accords with our stereotype of someone who quite likely would be active in the feminist movement. It is this stereotype that then guides our thinking so as to lead us to conclude that being a bank teller and being active in the feminist movement are most likely true. Shelia fits this stereotype, hence she surely is very likely to be active in the feminist movement.

‘Health’ warning

Again we need to issue a ‘health warning’ because not everyone agrees with this. An alternative account is that people are not so much seduced by the representativeness bias but they are reasoning in a very particular way when they are asked about what is most probable. To address this, we can ask, ‘Do people really not understand how the world operates or is it something more peculiar about understanding what ‘probable’ means?’

Well, one way in which this has been addressed has been to ask about Shelia, and then ask a very similar question about Walter. When we ask about Shelia, we will stick to using the term ‘probable’ but when we ask about Walter we will ask that the participant considers ‘how many’ other people fit Walter’s description.

In broad terms, the evidence shows that people are far less likely to make the conjunction error when probed with the “how many” question than the corresponding “how probable” question.

Nonetheless, we can now go onto to test the reliability of this finding and in the next step we will do this via our next Class Exercise.