Those who are unfamiliar with certain statistical rules may not realize how their judgement is being swayed by illogical, emotional, and unreliable intuition.Kahneman delved into statistics and how important an understanding of statistics is to good judgement (chapters 15, 16 and 17). Even the most scholarly, who are well versed in statistics, tend to have a difficult time fighting their intuitive perceptions. They often will make the logical decision but it may leave them with an irritating feeling of uneasiness, nonetheless.

Chapter 15 describes the pursuit for evidence about “the role of heuristics in judgement and of their incompatibility with logic” (p.156). Daniel Kahneman and Amos Tversky came up with an experiment that described a person named, “Linda”. Then they provided a list of eight scenarios and asked two groups to rank the example scenarios in terms of “representativeness” (group 1) or “probability” (group 2). The list included scenarios such as: “Linda is a bank teller”; “Linda is a bank teller who is active in the feminist movement”; “Linda is a teacher in an elementary school”; “Linda is a member of the League of Women Voters”, etc.. 

The conflict was found when people let the scenarios with more details similar to the description they had read earlier of Linda, outweigh the statistical probability that Linda was a member of that scenario. That is, the more details included in a scenario may appear to be more representative of the description of Linda but would actually be statistically less probable… think of a venn diagram. The more information, the smaller the section in the venn diagram and therefore, the less probable. The less detailed scenario would be a larger area on the venn diagram and therefore have a higher probability. This is simple logic but it conflicts so sharply with what we feel we know about Linda based on her description, even when we are told that the description may be unreliable. We cling to an intuitive feeling that the more detailed description is more likely or probable – which is completely untrue… statistically. Nevertheless, the intuitive feeling tends to be linked with stronger and more certain emotional judgement than the statistically correct choice which tends to be accompanied by feelings of uncertainty and unease.

Kahneman then states that, “the word fallacy is used, in general, when people fail to apply a logical rule that is obviously relevant” (p.158). He goes on to talk about a term they coined called the “conjunctive fallacy”, which is when people combine multiple descriptors in the scenario and think that the less probable scenario with more descriptors is more representative (or stereotypical) and therefore more “plausible”. For example, one may judge the conjunction of bank-teller and feminist as more plausible than just bank teller alone, when it is actually less probable. Kahneman states, “The most coherent stories are not necessarily the most probable, but they are plausible, and the notions of coherence, plausibility, and probability are easily confused by the unwary” (p. 159).

It is great that Kahneman and Tversky documented this phenomenon and made us more conscious and able to understand better the intuitive pull of the wrong choices and the strange uneasiness that comes with the correct choices. Kahneman goes on to state that, “the prevalence of bias in human judgement is a large issue” and how in courtrooms and politics the “focus on weakness” is used to raise doubts. I assume he is suggesting that raising doubts leads to the “power of judgement heuristics” (p.164) due to the additional information creating a conjunctive fallacy and people feeling very good and confident in their incorrect judgements, decisions, and resultant behavior. Rather than isolating the important information and making the more difficult but correct choice.

Reference

Kahneman, D. (2011). Linda: Less is more. In Thinking Fast and Slow (pp. 156-165). New York, NY: Farrar, Straus and Giroux.