What are heuristics? Representative vs. availability heuristics

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One topic that many of my psychology tutoring students get confused about is the topic of heuristics, which comes up when they study judgment and decision-making.

What is a heuristic?

A heuristic is a rule-of-thumb. It is a shortcut to solving a problem when you’re too lazy or overwhelmed or otherwise unable to solve it the proper way.

Here’s an example. Let’s say someone asked you: “Hey! How long is the gestational period of the African elephant?”

The proper response to this strange question would be to say, “Hmm, I don’t know. Hold on one second, let me check.” At this point, you would pull out your smartphone and Google until you stumble upon the Wikipedia page for gestational periods of various mammals. But what if you didn’t have your phone on you, or you didn’t feel like taking it out of your bag? Then you might say, “Hmm, well, the gestational period for humans is about 9 months, but elephants are bigger, so I’m gonna say…15 months?” (The correct answer is 645 days, or about 21 months).

So you would be wrong, but hey, it’s a weird question anyway, and you were kind of close. [If $10,000 or your reputation were on the line, then you’d probably take the time to Google.] This is the heuristic approach to answering the question because you used some information you already knew to make an educated guess (but still a guess!) to answer the question.

Heuristics come in all flavors, but two main types are the representativeness heuristic and the availability heuristic. Students often get these confused, but I’m going to see if I can clear up how they’re different with the use of some examples.

The Availability Heuristic

The availability heuristic is when you make a judgment about something based on how available examples are in your mind. So, this heuristic has a lot to do with your memory of specific instances and what you’ve been exposed to. Some examples:

  • Judging the population of cities (when cities are more available in your mind, like New York or Berlin, you will overestimate their populations).

  • Judging the frequency of deaths from different causes (morbid, I know). People tend to overestimate the number of deaths from, say, airplane crashes, but underestimate the number of deaths from, say, asthma. This is because people hear about deaths from airplane crashes in the news, so they can bring to mind a fair number of examples of this, but they can’t bring to mind examples of people dying from asthma. This is why reading the news can actually be misleading, since rare instances can be covered to the point of seeming commonplace.

  • One of my favorite examples: “Are there more words that begin with “r” or that have “r” as their third letter?” To answer this question, you can’t help but bring specific words to mind. Words that begin with “r” are easy to think of; words that have “r” as their third letter are harder to think of, so many people answer this question with “words that begin with ‘r’” when in fact, that’s the wrong answer.

The Representative Heuristic

On to representativeness. These decisions tend to be based on how similar an example is to something else (or how typical or representative the particular case in question is). In this way, representativeness is basically stereotyping. While availability has more to do with memory of specific instances, representativeness has more to do with memory of a prototype, stereotype or average. Let me try to make this clear with some examples:

  • “Linda the bank teller” – this is one of the most famous examples. It comes from the work of Kahneman and Tversky. In this problem, you are told a little bit about Linda, and then asked what her profession is likely to be. Linda is described as an avid protester who went to an all girls’ college. She is an environmentalist, politically liberal, etc. (I’m making up these details, but the information that subjects got in this study is quite similar). Basically, she’s described in such a way that you can’t help but think that she must be a feminist, because the prototype/stereotype that you have in your head is that women who are like Linda are feminists. So when people are asked if Linda is more likely to be a bank teller (working for The Man!) or a feminist bank teller, most people say the latter, even though that doesn’t make any sense, in terms of probability. In this case, people use a shortcut that involved a stereotype to answer the question, and they ignored actual likelihoods.

  • “Tom W.” – another classic example. Even when you know that people are way more likely to be psychology majors than engineering majors, people still say that Tom W. is likely to be an engineer, when he was originally described as a nerd. You know - someone who plays video games, likes building things, doesn’t have the highest social IQ. We think engineers tend to be like that, and that people like that tend to be engineers, so we’ll ignore the facts and go with a stereotype.

I can see why representativeness and availability seem similar, because when you use these heuristics, you are always using information that you had in the past to make a guess. But representativeness is less about particular examples, and more about stereotypes (which are probably formed on the basis of examples, but it’s often unclear where the stereotype even originated!). Availability is about particular examples and how readily they come to mind. This is why we tend to use availability when judging the number of things, because counting examples that come to mind is one way to answer that kind of question.

Heuristics on AP or GRE Psychology Tests 

I hope that was helpful, or at least fun! Another psychology tutor tip I have for you, if you’re preparing for the AP Psych or GRE Psych tests, is that these tests tend to use examples that you probably have come across in your review already. So if you memorize which examples go with which heuristics, that’s another way to answer those questions correctly. Obviously, trying to abstract the underlying principles behind the two heuristics is a lot better, but if you’re studying to the test, definitely memorize the famous examples.

For more information about heuristics, biases and decision-making, check out Nobel Laureate Daniel Kahneman’s book Thinking Fast and Slow.


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