study guide
12
Judgment and Reasoning
Judgment The activity of “thinking” takes many forms, but one of the central forms is judgment-the process through which people draw conclusions from the evidence they encounter, often evidence provided by life experiences. But how-and how well-do people make judgments? Experience is, of course, an who, after many seasons, tells you which game strategies work and which ones don’t. Likewise, you trust the police detective who asserts that over the years he’s learned how to tell whether a suspect extraordinary teacher, and so you’re likely to believe the sports coach is lying. You welcome the advice of the hair stylist who says, “I can tell you from the hair I cut every day, this shampoo repairs split ends.”
But we can also find cases in which people don’t learn from experience: “He’s getting married again? Why does he think this one will last longer than the last four?”; “It doesn’t matter how many polite New Yorkers she meets; she’s still convinced that everyone from that city is rude.”
What’s going on here? Why do people sometimes draw accurate conclusions from their experience, and sometimes not? Attribute Substitution Let’s start with the information you use when drawing a conclusion from experience. Imagine that you’re shopping for a car and trying to decide if European know how often these cars break down and need repair-how frequent are the problems? As a cars are reliable. Surely, you’d want to different case, imagine that you’re trying to choose an efficient route for your morning drive to work. Here, too, the information you need concerns frequencies: When you’ve gone down 4th Avenue, how often were you late? How often were you late when you stayed on Front Street instead?
Examples like these remind us that a wide range of judgments begin with a frequency estimate- an assessment of how often various events have occurred in the past. For many of the judgments you make in day-to-day life, though, you don’t have direct access to frequency information. You probably don’t have instant access to a count of how many VW’s break down, in comparison to how many ow, therefore, do Hondas. You probably don’t have a detailed list of your various commute times. you proceed in making your judgments?
Let’s pursue the decision about commuting routes. In making your choice, you’re likely to do a quick scan through memory, looking for relevant cases. If you can immediately think of three occasions when you got caught in a traffic snarl on 4th Avenue and can’t think of similar occasions on Front Street, you’ll probably decide that Front Street is the better bet. In contrast, if you can recall two horrible traffic jams on Front Street but only one on 4th Avenue, you’ll draw the opposite conclusion. The strategy you’re using here is known as attribute substitution- a strategy in which you rely on easily assessed information as a proxy for the information you really need. In this judgment about traffic, the information you need is frequency (how often you’ve been late when you’ve taken one route or the other), but you don’t have access to this information. As a substitute, you base your judgment on availability-how easily and how quickly you can come up with relevant examples. The logic is this: “Examples leap to mind? Must be a common, often-experienced event. A struggle to come up with examples? Must be a rare event”.
This strategy-relying on availability substitution known as the availability heuristic (Tversky & Kahneman, 1973). Here’s a different type of attribute substitution: Imagine that you’re applying for a job. You hope that the employer will examine your credentials carefully and make a thoughtful judgment about whether you’d be a good hire. It’s likely, though, that the employer will rely on a faster, easier strategy. Specifically, he may as a substitute for frequency-is a form of attribute barely glance at your résumé and, instead, ask himself how much you resemble other people he’s hired who have worked out well. Do you have the same mannerisms or the same look as Joan, an employee that he’s very happy with? If so, you’re likely to get the job. Or do you remind him of Jane, an employee he had to fire after just two months? If so, you’ll still be looking at the job ads tomorrow In this case, the person who’s interviewing you needs to judge probability that you’d work out well if hired) and instead relies on resemblance to known cases. This a probability (namely, the substitution is referred to as the representativeness heuristic. The Availability Heuristic People rely on heuristics like availability and representativeness in a wide range of settings, and so, if we understand these strategies, we understand how a great deal of thinking proceeds. (See Table 12.1 for a summary comparison of these two strategies.)
In general, the term heuristic describes an efficient strategy that usually leads to the right answer. The key word, however, is “usually,” because heuristics allow errors; that’s the price you pay in order to gain the efficiency. The availability and representativeness heuristics both fit this profile. In each case, you’re relying on an attribute (availability or resemblance) that’s easy to assess, and that’s the source of the efficiency. And in each case, the attribute is correlated with the target dimension, so that it can serve as a reasonable proxy for the target: Events or objects that are frequent in the world are, in most cases, likely to be easily available in memory, so generally you’ll be fine if you rely on availability as an index for frequency. And many categories are homogeneous enough so that members of the category do resemble one another; that’s why you can often rely on resemblance as a way of judging probability of category membership.
Nonetheless, these strategies can lead to error. To take a simple case, ask yourself: “Are there more words in the dictionary beginning with the letter R (rose, ‘rock, rabbit) or more words with an R in the third position (tarp, ‘bare; ‘throw)?” Most people insist that there are more words beginning with R (Tversky & Kahneman, 1973, 1974), but the reverse is true-by a margin of at least 2- to-1.
Why do people get this wrong? The answer lies in availability. If you search your memory for words starting with R, many will come to mind. (Try it: How many R-words can you name in 10 seconds?) But if you search your memory for words with an R in the third position, fewer will come up. (Again, try this for 10 seconds.) This difference, favoring the words beginning with R, arises because your memory is organized roughly like a dictionary, with words that share a starting sound all grouped together. As a result, it’s easy to search memory using “starting letter” as your cue; a search based on “R in third position” is more difficult. In this way, the organization of memory creates a bias in what’s easily available, and this bias in availability leads to an error in frequency judgment. The Wide Range of Availability Effects The R-word example isn’t very interesting on its own-after all, how often do you need to make judgments about spelling patterns? But other examples are easy to find, including cases in which people are making judgments of some importance.
For example, people regularly overestimate the frequency of events that are, in actuality, quite rare (Lichtenstein, Slovic, Fischhoff, Layman,&Combs, 1978). This probably plays a part in people’s willingness to buy lottery tickets; they overestimate the likelihood of winning. Likewise, physicians often overestimate the likelihood of a rare disease and, in the process, fail to pursue other, more appropriate, diagnoses (e.g., Elstein et al., 1986; Obrecht, Chapman, & Gelman, 2009).
What causes this pattern? There’s little reason to spend time thinking about familiar events (“Oh, look-that airplane has wings!”), but you’re likely to notice and think about rare events, especially rare emotional events (“How awful-that airplane crashed!”). As a result, rare events are likely well recorded in memory, and this will, in turn, make these events easily available to you. As a to be consequence, if you rely on the availability heuristic, you’ll overestimate the frequency of these distinctive events and, correspondingly, overestimate the likelihood of similar events happening in the future.
Here’s a different example. Participants in one study were asked to think about episodes in their lives in which they’d acted in an assertive manner (Schwarz et al., 1991; also see Raghubir & Menon, 2005). Half of the participants were asked to recall 6 episodes; half were asked to recall 12 episodes. Then, all the participants were asked some general questions, including how assertive overall they thought they were. Participants had an easy time coming up with 6 episodes, and so, using the availability heuristic, they concluded, “Those cases came quickly to mind; therefore, there must be a large number of these episodes; therefore, I must be an assertive person.” In contrast, participants who were asked for 12 episodes had some difficulty generating the longer list, so they concluded, “If these cases are so difficult to recall, I guess the episodes can’t be typical for how I act.”
Consistent with these suggestions, participants who were asked to recall fewer episodes judged themselves to be more assertive. Notice, ironically, that the participants who tried to recall more episodes actually ended up with more evidence in view for their own assertiveness. But it’s not the quantity of evidence that matters. Instead, what matters is the ease of coming up with the episodes. Participants who were asked for a dozen episodes had a hard time with the task because they’d been asked to do something difficult-namely, to come up with a lot of cases. But the participants seemed not to realize this. They reacted only to the fact that the examples were difficult to generate, and using the availability heuristic, they…
