Social Cognition and the SoCalled Conjunction Fal

Authors: John B Davies Anthony Anderson Dawn Little

Publish Date: 2011/07/13

Volume: 30, Issue: 3, Pages: 245-

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Abstract

The socalled ‘conjunction effect’ in which participants incorrectly assert that an instance from the conjunction of two sets is more probable than an instance from one of the two conjoining sets alone has been a source of debate as to whether it is a genuine fallacy of individual thinking or not We argue that reasoning about individuals follows a different process than reasoning about sets 35 participants took part in 3 tasks a one involving blocks of different sizes and colours designed to evoke setbased reasoning b one where a particular block was ‘individuated’ by stating that it represented a particular person and c the original Tversky and Kahneman Psychological Review 904293–315 1983 ‘Linda’ problem As predicted setbased reasoning was significantly more prevalent for the blocks task than for the other two tasks Participants’ reasons for their choices suggest that some individuals correctly use setbased logic in one task and a social reasoning process for the other tasksThe box of blocks is then removed from view by covering them the blocks will remain hidden for the rest of the session then the participant is asked the following questions ‘Suppose I draw a block from the box at random and that I can just as easily pick one of any size and of any colourBlocks remain hidden from view throughout The participant is instructed ‘Consider the box of bocks again Imagine that each one symbolises a particular individual Imagine that one of the individuals involved is called Susan Imagine also that the real person Susan is keen on nature on preserving the natural environment and on outdoor pursuits like hill walking and mountain climbing Is the block that represents Susan most likely to be Green Large or Green and Large Participant makes a choice Why Their verbal response is notedThe participant is presented with following information ‘Linda is 31 years old outspoken and very bright She majored in philosophy As a student she was deeply concerned with issues of discrimination and social justice and also participated in antinuclear demonstrations’ They are then asked ‘Is Linda most likely to be a feminist a bank teller or a feminist bank teller’ Participant makes a choice Why Their verbal response is noted

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