One of the things I love about reading and researching for this blog is finding brain quirks that I would describe as \u201chidden in the open.\u201d\u00a0 When Jules and I write about heuristics in this space, they often strike me as patently obvious brain traits.\u00a0 Something I might have discovered on my own if I had a little more mental horsepower. This\u2019s month heuristic-of-choice is one of those. For this month, I\u2019m going to dust off an old heuristic that is new to the blog.\u00a0 The \u201crepresentativeness heuristic.\u201d\u00a0 But, first, let\u2019s refresh, if needed, on what a heuristic is.\u00a0 Loosely defined, it\u2019s a scientifically demonstrated mental shortcut that is prevalent in human thinking or decision making.\u00a0 Heuristic short-cuts help us think and react quickly, but they can also lead us to wildly inaccurate conclusions.<\/p>\n
Let\u2019s start with this scenario.\u00a0 Let\u2019s say I gave you the following description of a person: \u201cSusan is 39 years old and is successful in her career.\u00a0 She\u2019s articulate, friendly, detail-oriented, and analyzes problems thoroughly. She opened her own office 3 years ago.\u201d\u00a0 Now, let\u2019s suppose that I said, \u201cSusan is either a lawyer or an engineer. Which career does Susan have?\u201d\u00a0 First, go ahead and blurt out an answer based on the description.\u00a0 Now, as you think through it after the fact, take note of what your thought processes are actually doing here; what they\u2019re focusing on.\u00a0 Suppose I add this twist into the experiment: \u201cSusan is one person in a room of 100 professionals.\u00a0 75% of these people are engineers and 25% of them are lawyers.\u00a0 Based on how I\u2019ve described Susan above, is she an engineer or is she a lawyer?\u201d[1]<\/a><\/p>\n In the representativeness heuristic, we are making predictive decisions based on \u201cthe degree to which A is representative of B, that is, by the degree to which A resembles B.\u201d[2]<\/a> It\u2019s worth thinking for a second how prevalent this breed of analysis is in courthouse decision-making.\u00a0 The authors of the article I\u2019m writing on here frame the kinds of questions where we employ this heuristic as follows: \u201cWhat is the probability that object A belongs to class B?\u00a0 What is the probability that event A originates from process B?\u00a0 What is the probability that process B will generate event A?\u201d[3]<\/a>\u00a0 Can you frame those as trial-process questions?\u00a0 Surely.\u00a0 \u201cWhat is the probability that A is the kind of person to commit this B-type crime?\u00a0 What is the probability that crash A originated from driving-behavior B?\u201d<\/p>\n Let\u2019s go back for a moment to the example above where we know how we describe Susan and we also know the number of engineers and lawyers in the room.\u00a0 It\u2019s a very clear fact of math that if you have 75 engineers in a room and add in 25 lawyers, the probability that one randomly chosen person in the room will be an engineer is pretty high.\u00a0 However, experiments on this same kind of scenario I have given you have shown that most people ignore the rock-solid percentages in favor of predicting from some mushy notion of representativeness.[4]<\/a> If you have picked apart your own thinking about Susan, you\u2019ve likely uncovered a fundamental truth of the representativeness heuristic: we largely answer these questions by resorting to stereotypes.[5]<\/a>\u00a0 We\u2019ll get stereotypical ideas in our head about lawyers and engineers and then will see if the things we know about Susan match those representations.\u00a0 \u201cArticulate?\u00a0 Gotta be a lawyer because engineers are quiet, awkward types and lawyers are wordsmiths. \u00a0Friendly?\u00a0 You better be if you want to keep your clients!\u00a0 Working for herself?\u00a0 She started her own law firm to be free from toxic office politics!\u00a0 You go, Susan.\u201d\u00a0 Let\u2019s be honest.\u00a0 Perhaps you also whispered to yourself at some point, \u201cDidn\u2019t my brother\u2019s first college roommate once say that most engineers are men?\u201d[6]<\/a>\u00a0 You have no actual hard data, but the stereotype is accessible.<\/p>\n We might benignly hang fast to the idea that Susan is a lawyer from what we know of her.\u00a0 No harm comes to us via our Susan-decision today.\u00a0 However, the fact that we will often ignore the relevant predictive criteria, such as the high percentage of all the engineers in the room could, in some other context, be rather devastating.\u00a0 Just the other day, my wife was telling me about a statement another juror kept repeating to the other jury members while they all deliberated after a rape trial: \u201cI know he\u2019s guilty just by the way he was looking at [so-and-so].\u201d\u00a0 In other words, \u201cPeople who look at other people the way he was looking are the kind of people who would commit a rape.\u201d\u00a0 Thankfully, other jurors put that representativeness heuristic in check, and the jury couldn\u2019t otherwise reach a verdict on the real pieces of evidence in front of them. That juror, however, never abandoned his guilty vote.<\/p>\n Well, lawyer family, Susan is an engineer.\u00a0 At least in my head and for the purposes of this blog post. \u00a0She\u2019s very well spoken, is kind to kids and little old ladies, and her firm has designed every bridge this side of the Ozarks. Were she real, she\u2019d be susceptible to heuristic errors too. All this talk of lawyers and mental short-cuts makes me think of one very notable legal-version of the representativeness heuristic.\u00a0 An example of wild stereotyping that lives rent-free in my head.\u00a0 I\u2019ve mentioned it once already in this space.\u00a0 It\u2019s Clarence Darrow\u2019s 1936 state-of the-art (or so it was believed to be at the time) work on picking a winning jury during voir dire. <\/em>He was trying to answer the question, \u201cWill person A be in the class of persons likely to produce verdict B?\u201d\u00a0 It\u2019s hard to believe the following answers were ever considered state-of-the-art: \u201cThe Englishman is not so good as an Irishman\u2026The German is not so keen about individual rights except where they concern his own way of life\u2026Beware of the Lutherans, especially the Scandinavians…\u201d[7]<\/a>\u00a0 It\u2019s an old cautionary tale, for sure, but modern experiments have proven our thinking to be similarly susceptible.<\/p>\n <\/p>\n ———————<\/p>\n [1]<\/a> The hypothetical presented in the text is adapted from experimental data discussed in Amos Tversky & Daniel Kahneman, Judgment Under Uncertainty: Heuristics and Biases<\/em>, 185 Science 1124, 1124\u201325 (1974), although certain facts and numerical values have been modified for illustration in this forum and for this audience.<\/p>\n [2]<\/a> Id<\/em>. at 1124.<\/p>\n [3]<\/a> Id.<\/em><\/p>\n [4]<\/a> Id. <\/em>at 1125.<\/p>\n [5]<\/a> Id<\/em>.<\/p>\n