Learning By DoingPop quiz! Do your best to answer the following questions.
- Since 1994, the homicide rate in the US has: risen sharply, risen slightly, stayed the same, fallen slightly, or fallen sharply.
- After a plane crash, people's estimates of air traffic accidents: increases, decreases, or stays the same.
- Bad things always happens in threes. Do you: strongly agree, slightly agree, not have any feelings one way or the other, slightly disagree, or strongly disagree.
Your Information EcologyLast time, we talked about the confirmation bias. We explored how the mind uses shortcuts to gather information and make judgements about the world. In addition to the confirmation bias, the mind uses many other shortcuts. One of these is the availability bias, which states that our judgments of the "truthiness"  of a given statement is based on how easily relevant information comes to mind .
Consider the following example. Is the suicide rate among Americans higher or lower than the homocide rate? Stop for a second and think about your answer. Then, pause again and ask yourself how you formed your answer. What information did you draw upon? What long-term memories did you consult?
If you're like me, then you might be surprised to learn that the suicide rate is almost double the homicide rate . If that surprises you, then consider why you thought that the homicide rate was higher. One reason might be because the media reports more stories about homicide than suicide. Therefore, the information we are exposed to does not reflect the actual rates (i.e., there are more news reports of homicide even though the suicide rate is higher). We are influenced by the information that is available (hence the name of this bias).
Availability Mechanisms: How Often and When?Much of the early work on "heuristics and biases" was conducted by a team of psychologists named Daniel Kahneman and Amos Tversky. In one of their papers, they empirically demonstrated the availability bias with a very simple manipulation . First, they created two lists of 39 names. The first list contained 19 names of famous women and 20 non-famous men's names. The second list was the exact opposite. It featured 19 famous men (and 20 non-famous women's names). After constructing the two lists, they asked people to listen to them and estimate if the list had more names of men or women. Can you guess what they found?
In the list containing famous women, participants estimated that there were more woman than men in the list, even though there was actually one fewer female name in the list. The reason this works is because the participants were able to easily recall the name of the woman in the list (and less able to recall men's names).
In their paper, Tversky and Kahneman proposed several potential mechanisms for the availability bias. First, easily generated ideas, thoughts, and memories are the ones that are the most frequently encountered. For example, you see your family members and coworkers more often than your distant cousins or high-school classmates. When asked to name the people you know, it is more likely that you will name the people you see everyday than those whom you haven't seen in years.
Another property that has an impact on the fluent generation of ideas and memories is recency. It is easier to recall the names of people, places, and things that you've recently encountered. As they say: Out of sight, out of mind.
In summary, the frequency and recency of exposure to information can have a large impact on how easily ideas and memories are called to mind.
The S.T.E.M. ConnectionScientific thinking is synonymous with critical thinking, and knowing about the availability bias might help students become more critical of the information they hear reported in the news. They might also become a little more skeptical of their own beliefs. For example, if they hear someone claim, Bad things happen in threes, they might realize that the claim is based on the (false) notion that, "It must be true because I can think of lots of examples." The same might be true in designing a hypothesis to test. Just because you can easily imagine an outcome to the experiment doesn't make it more true (or likely).
In conclusion, it is handy to know about cognitive biases. Why? Although you might not become immune to them, it might help reduce their impact (see also the post on metacognition). An understanding of the availability bias might help students better calibrate their view of the world if they realize that frequent and recent information can influence their thinking. In the immortal words of G.I. Joe: Knowing is half the battle. Battle on my friends...and don't be heavily swayed by the first thing that pops into your mind!
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Going Beyond the Information Given In case this term is new to you, truthiness was coined by Stephen Colbert on his show, The Colbert Report.
 Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive Psychology, 5(2), 207-232.
 According to this Freakonomics podcast, there were "36,500 suicides in the U.S. and roughly 16,500 homicides" in 2009.
 Tversky, A., & Kahneman, D. (1973). Availability: A heuristic for judging frequency and probability. Cognitive psychology, 5(2), 207-232.