When making decisions or judgments, we often use mental shortcuts or "rules of thumb" known as heuristics. For every decision, we don't always have the time or resources to compare all the information before we make a choice, so we use heuristics to help us reach decisions quickly and efficiently. Sometimes these mental shortcuts can be helpful, but in other cases they can lead to errors or cognitive biases.
The representativeness heuristic is one type of heuristic that we use when making judgments. In this particular example, we estimate the likelihood of an event by comparing it to an existing prototype that already exists in our minds. Our prototype is what we think is the most relevant or typical example of a particular event or object.
The representativeness heuristic was first described by psychologists Amos Tversky and Daniel Kahneman during the 1970s. Like other heuristics, making judgments based upon representativeness is intended to work as a type of mental shortcut, allowing us to make decisions quickly. However, it can also lead to errors. When we make decisions based on representativeness, we may be likely to make more errors and more likely to overestimate the likelihood that something will occur. Just because and event or object is representative does not mean that it is more likely to occur.
Consider the following description:
Sarah loves to listen to New Age music and faithfully reads her horoscope each day. In her spare time, she enjoys aromatherapy and attending a local spirituality group.
Based on the description above, is Sarah more likely to be a school teacher or a holistic healer? Many people would identify her as a holistic healer based on representativeness. She fits in with our existing ideas of how a holistic healer might behave. In reality, it is far more likely that Sarah is actually a school teacher based purely on probability. School teachers are far more common than holistic healers.
In their classic experiment, Tversky and Kahneman presented the following description to a group of participants:
"Tom W. is of high intelligence, although lacking in true creativity. He has a need for order and clarity, and for neat and tidy systems in which every detail finds its appropriate place. His writing is rather dull and mechanical, occasionally enlivened by somewhat corny puns and by flashes of imagination of the sci-fi type. He has a strong drive for competence. He seems to feel little sympathy for other people and does not enjoy interacting with others. Self-centered, he nonetheless has a deep moral sense."
The participants were then divided into three separate groups and each group was given a different task.
- The first group was asked how similar Tom was to one of nine different college majors. The majority of participants in this group believed Tom was most similar to an engineering major and least similar to a social science major.
- Participants in the second group were asked to rate the probability that Tom was one of the nine majors. The probabilities given by the participants in the second group were very similar to the responses given by those in the first group.
- In the third group, participants were asked a question unrelated to Tom's description. They were asked to estimate what percentage of first-year graduate students were in each of the nine majors.
What the researchers found was that people were highly likely to believe that Tom was an engineering major, despite the fact that there was a relatively small number of engineering students at the school where the study was conducted. People were likely to believe that Tom was an engineering major based on representativeness, ignoring other pertinent information such as the small number of engineering students.
Observations and Examples
- "The representativeness heuristic is the tendency to judge the frequency or likelihood of an event by the extent to which it resembles the typical case. For example, in a series of 10 coin tosses, most people judge the series HHTTHTHTTH to be more likely that the series HHHHHHHHHH (where H is heads and T is tails), even though both series are equality likely. The reason is that the first series looks more random than the second series. It "represents" our idea of what a random series should look like."
(Roy F. Baumeister & Brad J. Bushman, Social Psychology and Human Nature, 2011) - "The representativeness heuristics affects many real-life judgments and decisions. For example, jury decisions depend partly on the degree to which a defendant's actions are representative of a particular crime category. So someone who abducts a child and asks for ransom is more likely to be convicted of kidnapping than someone who abducts and adult and demands no ransom. Both crimes constitute kidnapping, but the first is a more representative example."
(Douglas A. Bernstein, Essentials of Psychology, 2011) - "For an illustration of judgment by representativeness, consider an individual who has been described by a former neighbor as follows: "Steve is very shy and withdrawn, invariably helpful, but with little interested in people, or in the world of reality. A meek and tidy soul, he has a need for order and structure, and a passion for detail." How do people assess the probability that Steve in engaged in a particular occupation form a list of possibilities (for example, farmer, salesman, airline pilot, librarian, or physician)? ... In the representativeness heuristic, the probability that Steve is a librarian, for example, is assessed by the degree to which his is representative of, or similar to, the stereotype of a librarian."
(Amos Tversky & Daniel Kahneman, "Judgment Under Uncertainty: Heuristics and Biases," 1974)
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