28 February 2013

Your Memory Is Not the Real World - Availability Heuristic

Imagine yourself as being the parent of a 9 years old child who wants to go and play with a colleague from school at his house. As any loving parent you want your child to be happy (play with the colleague) and you also want your child to be safe (not be endangered). The colleague’s family is a regular family with nothing suspicious about them. Consider that you know only one thing apart from that family being “average”.

Situation1. You know that that family has a gun (pistol) with “live ammunition” in the house.

Would you let your child go and play at the colleague’s house? YES or NO?

Very likely your answer is “No”. You want to be a good parent and protect your child from harm and guns are dangerous even in the hands of adults; there is no telling how dangerous they are in the hands of children.  

Taking a step back, think a bit about the actual probability of the kids finding the gun without  searching for it, playing with it, actually firing it and actually hitting and hurting one of them. Of course, they would need to be without adult supervision for quite some time to be able to do all of the above.

What is your answer now? Probably your answer is unchanged. All the things in the paragraph above make some sort of sense, but you know “GUNS are DANGEROUS”. OK! Fair enough!

Situation 2. You know that the family has a swimming pool in the backyard.

Would you let your child go and play at the colleague’s house? YES or NO?

Very likely your answer is “Yes”. If they have a swimming pool it means that the children can have more fun playing around it.


When it comes to young children, swimming pools are much more dangerous than guns, at least according to Steven D. Levitt, Stephen J. Dubner authors of Freakonimics.

How come you failed at this? It is perfectly reasonable to assume that guns are more dangerous than swimming pools. After all you probably have heard of more deaths by guns than deaths by swimming pools.

The answer to this failure in judgment is “the availability heuristic” or how I like to call it sometimes “Observation bias”. Let’s see how it works.

The correct (rational) question you have to answer when assessing the potential threat to your child’s wellbeing is “what is the probability of my child getting hurt by a gun / swimming pool?”. The emphasis is on PROBABILITY! Giving it a bit of “cold” thought, virtually anything can be dangerous, thus you should see what is less likely to hurt your child.

As mentioned in previous posts, humans are not particularly good at assessing probabilities. Since it is hard to establish the exact probability of an event, we resort to heuristics. In other words we tend to give an answer to a difficult question (what is the probability?) by answering an easier question (how many instances of an event do I know of?).

To make this a bit clearer, people assess probabilities of events in the world by evaluating the number of those events that they can remember. Not surprisingly, what we have stored in our memory is different from what is actually happening in the “real world”.

Let me give you another example of this availability heuristic from my own life. In 1991 I had my first trip outside my home country – Romania and went with my mother in the UK. I was about 9 years old at the time. Our hosts were very generous and friendly and they wanted us to get to know as much as possible about regular life in the UK, so they arranged for us to meet with many of their friends.

One lady was very surprised to see that I (a Romanian child) was a regular normal child. Now, I know that westerners had (and still have) some really stereotypical views on easterners, but this went far beyond the “eastern stereotype”. The lady was surprised to see that I was healthy in both body and mind.

The reason for this lady’s astonishment in seeing that a Romanian child can be normal was due to the fact that the BBC had presented a story on the conditions in a Romanian orphanage. The story is horrifying. In a nutshell, the communist dictatorship regime decided that children with mental disabilities are not worth the effort and kept them in inhumane conditions waiting for them to die.

The British lady had in her memory these images, thus she somehow implied that all (or most) of Romanian children are disabled. Surprise! It is not so!    

In an earlier post - DespiteSeldom Encounters With Foreigners or Immigrants Some People Have StrongXenophobic and Racist Attitudes…  I have addressed the issue of racism and xenophobia through the lenses of the availability heuristic. The main idea is that when it comes to negative attitudes towards immigrants, many people simply make judgments based on what is available in their memory on the issue of “immigrants” and due to the free press most likely when they think of “immigrants” the first things that come into mind are the negative stories that got large coverage in the media.

However, most immigrants are regular hard working people. The only issue is that no one notices these people because “going to work every day” is no subject for news. Read the post if you want to get more on this.  

Some criticism on the examples I gave until now on the availability heuristic is that the instances stored in memory of death by guns, immigrants that do bad things and disabled children are somehow emotional. I will address this issue in a future post on the “affect heuristic”.

Availability without affect exists and here is one example. Are there more words with the letter “R” as the first letter or are there more words with “R” as the third letter (English vocabulary)?

Most people go for “First letter” because words beginning with “R” such as “Race” come easier to one’s mind than words with “R” as a third letter such as “Mortgage”. However, as you very likely figured out, there are more words with “R” as the third letter than there are words with “R” as the first letter.

Another case of the availability heuristic is related not to how many instances of an event are available in memory, but rather to how vivid an event is memory. For example after the recent (15 February 2013) event when a meteorite fell in Russia, if you ask people what is the probability of a meteorite hitting the Earth, you will get higher estimates than you would have got if you would have asked (the same people) on the 15th of January 2013.

The reality is that the probability has not changed after the event, but the vividness of the event makes it seem more probable.

The implications of the availability heuristic in our everyday lives are significant. You might think that the examples about meteorites hitting the Earth and about guns and swimming pools are frivolous and to a certain extent you are right. At the same time, xenophobia and racism are major issues in a cosmopolite and globalized world. Going into less complex issues of society, many people are less happy because they overestimate risks such as an airplane crash and don’t take that trip to Iceland or wherever.

When assessing risks, think twice! Because your memory is not a good representation of the “real” world.
This post is documented from:
Tversky, Amos, and Daniel Kahneman (1974), "Judgment under Uncertainty: Heuristics and Biases," Science, 185, 1124-31.

Steven D. Levitt, Stephen J. Dubner (2005), “Freakonimics: A Rogue Economist Explores the Hidden Side of Everything”, New York: William Morrow Ltd. 

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