Heuristics: Availability Pt.1

As we explore this notion of heuristics, it is time to look at the availability heuristic. In this article, we will see what it is, how it works and examples of where it can take effect to cause an irrational outcome.

Essentially, the heuristic of availability[1] involves using examples and ideas that you already know, i.e. information available to you, to make an estimate on something else. It refers to the idea that people often rely on easily recalled information rather than actual data when evaluating the probability of a particular outcome.[2] For example, an individual may have seen more people using cars than buses, so they can guess that the likelihood of dying in a car accident is higher. In this case, they would be right – the bus occupant fatality rate was 45 deaths per 100,000 people in 2009, which was far less than for passenger car occupants, with the probability equalling 251 deaths per 100,000 people in the same year[3]. Obviously, these figures can vary from country to country and year to year, but the general estimate still holds true. This shows how the availability heuristic can be useful, as it is a mental shortcut that allows the individual to reach the correct outcome without having to find, extract and process the data. However, when an individual has imperfect or incomplete information in a particular situation, then the examples available to them that they plan on using can cause a false estimation that misleads the individual and results in irrational decisions.

A startling case of this irrationality caused by misconceptions is aeroplane crashes. When an aeroplane crashes, it is widely broadcasted in the news, and so it becomes present at the front of someone’s mind, creating a false idea that aeroplane crashes are common. In reality, the chances of dying in an aeroplane accident are 1 in 9821, or in perspective, there is, on average, one fatal accident for every 16 million flights. Compared to the figure of roughly 1 in 400 that we used for fatal car accidents earlier, it is clearly much less likely to occur. Despite this, the much more extensive news coverage of plane crashes means that people still irrationally fear going on planes but have no problem entering a car which is statistically almost 25 times more likely to kill them.

[1] Cognitive Psychology – ‘Availability: A Heuristic for Judging Frequency and Probability’ – Amos Tversky and Daniel Kahneman, 1973

[2] University Of Chicago – ‘Behavioural economics, explained’ – Max Witynski, 2020

[3] ‘Bus Accidents: Statistics ‘– Zinda Law Group, Data collected in 2009, study published in 2011

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