Availability bias

From credulism.com
Jump to: navigation, search

Summary: This article shows that availability bias - our cognitive bias towards basing our judgements on whichever relevant information is most readily available to our thought processes - can be explained by a combination of credulism, the certainty of belief, and the speed of the brain, and applies to any kind of judgement. This is contrary to the currently dominant theory that availability bias is restricted to judgements of the frequency and probability of types of events, and is the product of a cognitive heuristic - the availability heuristic - which operates on the principle that the availability, to our thought processes, of instances of a type of event indicates their frequency and probability.

1 Introduction


Availability bias is our cognitive bias towards basing our judgements on whichever relevant information is most readily available to our thought processes. That is, it's our universal tendency to jump to conclusions.

Availability bias was originally conceived in 1973 by Daniel Kahneman and Amos Tversky[1]. They proposed that it applies to judgements of the frequency and probability of types of events, and is the product of a cognitive heuristic - the availability heuristic - that operates on the principle that the availability, to our thought processes, of instances of a type of event indicates their frequency and probability. And this is still the dominant theory.

However, as the following chain of reasoning shows, availability bias actually applies to any kind of judgement, and isn't the product of a cognitive heuristic, but can be explained by a combination of credulism, the certainty of belief, and the speed of the brain[2].

2 The origin of availability bias


  1. When making a judgement, the relevant information that's most readily available to our thought processes will, by definition, enter those processes first.
    • For example, when trying to judge someone who we've just met, and know nothing about, what will tend to be most readily available to our thought processes, and which will therefore enter those processes first, is information about their physical appearance and body language, given that we start receiving such information upon the person simply entering our visual field.
  2. And our reasoning or imagination will, given the speed of the brain, tend to generate a possible judgement, X, based on what enters our thought processes first, before any more relevant information has had a chance to enter our thought processes.
    • In the example, if we see that the person’s clothes are old and tattered, then the possibility that they're poor might enter our thought processes, via our reasoning or imagination, before any direct information about their level of wealth has had a chance to enter our thought processes.
  3. However, given credulism and the certainty of belief, we'll be certain of X upon it entering our thought processes.
    • That is, although X is merely a possible judgement, based merely on what enters our thought processes first, it enters those processes as reality. As explained in Objections to credulism - in sub-section Objection 2 - X can't first enter our thought processes as merely the subject of another claim, and so can't first enter our thought processes as merely a possibility, given that that would require it to first enter our thought processes as the subject of the claim 'X is a possibility'.
    • In the example, if, upon us seeing the condition of the person’s clothes, the possibility that they're poor enters our thought processes, then we'll thereby be certain of this.
  4. And, as explained in Confirmation bias - in the section Belief is self-preserving - our certainty effectively provides a degree of protection to our beliefs, directly and via confirmation bias.
    • In the example, our certainty, while it exists, that the person is poor will mean that we'll tend not to be motivated to question the content or formation of our belief. And this will in turn mean that we'll tend not to be motivated to consider contrary possibilities - such as that the person may not be poor, but is dressed in such clothes because they're about to do some manual work, such as gardening, or because they're simply unconcerned about wearing such clothes.

      And our certainty, while it exists, will also mean that we'll not, by definition, be motivated to seek further information to test our belief, and will be biased towards interpreting any subsequent relevant information in a way that's consistent with our belief.

      Hence the common adages 'First impressions count', 'You never get a second chance to make a first impression', and 'Don’t judge a book by its cover'.

    • As also explained in Confirmation bias - in the section Belief is self-preserving - the certainty of belief, and the resulting confirmation bias, evidently don't prevent a belief from ever ceasing, and this may occur within a fraction of a second of it forming, given the speed of the brain - and we'll therefore likely have no recollection of it. Nevertheless, they mean that a belief endures even if the formation of a contrary belief, including simply a doubt, would only require a very small amount of thought.
    • In the example, it may occur to us, within a fraction of a second of us forming the belief that the person is poor, that their wealth doesn't necessarily correlate with the condition of their clothing, and that they therefore may not be poor - and we'll therefore likely have no recollection of our brief belief. But the certainty of belief, and the resulting confirmation bias, mean that we'll be biased against reaching this realisation.
  5. Therefore, we're biased towards basing our judgements on whichever relevant information is most readily available to our thought processes.


3 Noticing availability bias


Although availability bias permeates all reasoning, we tend not to notice instances of it, for several reasons.

Whether we do form a judgement based on whichever relevant information is most readily available to our thought processes tends to depend on whether our reasoning or imagination generates a possibility, based on that information, before any more relevant information has had a chance to enter our thought processes. And that depends on the nature of our intelligence and imagination, and on the nature and availability of the information. However, even if we don't form such a premature judgement, this is in spite of availability bias, not because it's absent.

Also, even if we do form a premature judgement, this belief may, as explained, cease within a further fraction of a second, and we'll therefore likely have no recollection of it. Our belief may be replaced by a contrary judgement, or we may simply conclude that we don't have sufficient information to form a judgement, and so need to suspend judgement until we do.

And even if a premature judgement endures for much longer than a fraction of a second, we still tend to fail to notice its premature nature, for the following four reasons:

  1. Given the certainty of belief, and that a judgement is a belief, we tend to not be motivated to analyse, and therefore question, the formation of our judgements. And such an analysis also doesn't, of course, occur involuntarily upon the formation of our judgements - indeed, that would lead to infinite layers of analysis, given that the conclusion of such an analysis would itself be a judgement.

    This explains why it's normally easier for us to notice other people jumping to conclusions than it is for them, or than it is for us to notice ourselves doing so: observing someone else’s judgement-formation involves, by definition, thinking about that process.

    Therefore, although we can analyse the formation of our enduring judgements whenever we want to, we tend not to. And we're less likely to do so the more time that has passed since the judgement was formed, or mundane its subject, or time-pressured we are. And however obviously premature our judgements may be, we'll not notice their premature nature unless we do analyse their formation.

  2. Even if we eventually change one of our enduring premature judgements, we still won't automatically analyse the formation of our original judgement. And, again, we're less likely to do so the more time that has passed since that original judgement was formed, or mundane its subject, or time-pressured we are.
  3. Even if we do analyse the formation of one of our enduring judgements, past or present, we may simply assume that it would have been based on more than what happened to enter our thought processes first. That is, given that we're questioning the basis of the judgement, the irrationality, by definition, of a premature judgement will naturally be likely to enter our mind, and, if it does, we may then wrongly assume that it would have also done so at the time of the judgement. We may even then retrospectively identify other apparent supporting facts, and assume that they would have been equally obvious to us at the time of the judgement, with this thought process being influenced by confirmation bias. And we're more likely to make these assumptions the more time that has passed since the judgement was formed, or significant its subject, or time-pressured we are.
  4. Even when we do realise the premature nature of one of our judgements, past or present, we don't realise, given the previous three points and the points preceding them, that such judgements permeate our reasoning.


4 Availability bias without an availability heuristic


As explained in the introduction, availability bias was originally conceived as only applying to judgements of the frequency and probability of types of events, and as being the product of a cognitive heuristic - the availability heuristic - that operates on the principle that the availability, to our thought processes, of instances of a type of event indicates their frequency and probability. And this is still the dominant theory. For example, the Oxford Dictionary of Psychology defines availability bias under the entry heading 'availability heuristic', and refers to the availability heuristic as a fact rather than a theory - 'The heuristic was first identified in 1973...' - and as solely applying to judgements of the frequency and probability of types of events[3].

In one of the original experimental illustrations of this bias, subjects were asked whether, in an average piece of writing, the letter 'k' occurs more frequently as the first letter of a word or as the third letter[1]. Most subjects said the former, although it's the latter, by about two to one. It's much easier to recall words beginning with a particular letter than words with that letter as the third letter - that is, the former are much more readily available to our thought processes. This is partly because the first letter of a word is, by the nature of its position, more prominent than the third. Also, as we consider the letter in question, we mentally hear its sound, which much more easily triggers our memory of words which begin with that sound than words which have that sound after their beginning. According to the original explanation for availability bias, we conclude, via the availability heuristic, that the greater availability, to our thought processes, of words beginning with 'k' than words with 'k' as the third letter is due to the former occurring more frequently in writings.

However, the outcome of the above experiment can be explained without reference to a cognitive heuristic. Upon trying to judge whether, in an average piece of writing, the letter 'k' occurs more frequently as the first letter of a word or as the third letter, the first type of word is, as explained, more readily available to our thought processes than the second. And the possibility that our much greater ease in recalling the first type of word than the second is due to the former occurring much more frequently in writings is a much simpler, and more obvious, explanation than the above two reasons. Also, given that we're judging the relative frequency of these two types of words, the possibility that one occurs more frequently than the other is necessarily already on our mind, whereas this isn't the case for the above two reasons. Therefore, the false explanation is much more likely to be generated by either our reasoning or imagination before the true one. And, given credulism and the certainty of belief, we'll be certain of it upon it entering our thought processes, with that certainty effectively providing a degree of protection to that belief, directly and via confirmation bias.

Also, the chain of reasoning in section 2 applies to any kind of judgement, not just those of the frequency and probability of types events. Indeed, in the example of meeting the person with old and tattered clothing, our likely judgement, due to availability bias, that they're hard up isn't such a judgement.


5 Sources

  1. 1.0 1.1 Tversky, A., and Kahneman, D., 1973, 'Availability: A Heuristic for Judging Frequency and Probability', Cognitive Psychology, volume 5, issue 2, pages 207-32.
  2. This argument first appeared, in a less advanced form, in:
    Farnell, D., 2013, 'How belief works', Think, volume 12, issue 35, pages 39-60.
  3. Colman, A.M., 2009, Oxford Dictionary of Psychology, 3rd edition, Oxford: Oxford University Press.


6 External links