If something is said often enough it must be true! – Availability Bias or the Illusory-Truth Effect

There is no place like home. There is no place like home. There is no place like home. There is no place like home.

yellloudWhile repeating the ending line to the Wizard of Oz may have worked well enough for Dorothy, it doesn’t work in the same way for us. Or does it? Sometimes it appears that people treat claims as true, or at least more valid, when they hear them regularly. One can easily find evidence of this when looking around on the internet. Through the ease of publication and promulgation in the modern era of social media, it is relatively easy for inaccuracies, misnomers and blatant lies to spread like wildfire. But why is it that even when they are obviously false, or resoundly corrected, that many people still believe them to be true? Well it seems that there is some truth to the old adage ‘if it is said often enough it becomes true.’
Welcome to Cognitive Bias Wednesday — today looking at the Availability Bias or the Illusory-Truth Effect.

Although hearsay, scuttlebutt and old-wives tales may account for some of the repeated claim evidence, it appears that the cognitive rabbit hole goes a bit deeper than this. In 1977 Hasher et. al. ran a study looking at how repetition of information affected the believability of it. 1 Surprisingly they found that not only did participants respond more confidently seeing the repeated information, the usual symptom of a Remember-Know task, but they also rated the validity higher, than the novel information. Their abstract for the piece highlights their findings succinctly:

Subjects rated how certain they were that each of 60 statements was true or false. The statements were sampled from areas of knowledge including politics, sports, and the arts, and were plausible but unlikely to be specifically known by most college students. Subjects gave ratings on three successive occasions at 2-week intervals. Embedded in the list were a critical set of statements that were either repeated across the sessions or were not repeated. For both true and false statements, there was a significant increase in the validity judgments for the repeated statements and no change in the validity judgments for the nonrepeated statements. Frequency of occurrence is apparently a criterion used to establish the referential validity of plausible statements. 2

morala-in-politica-if-you-repeat-a-lie-often-enoughOf the greatest surprise here is that final sentence: ‘frequency of occurrence is a criterion … [for the] validity of plausible statements.’ In other words they found that the more seemingly plausible material was repeated, the more it was believed as factual. To translate this into the modern social media era, take the seemingly ridiculous, but vaguely plausible, claims regarding ‘Chemtrails,’ fluoridated water or the ideology of ISIS. While the claims bear little to no factual basis, if repeated often enough they begin to attain an air of social plausibility. The facts surrounding the matters at hand have not changed one iota, but the more it is shared and re-shared, the more it is believed and repeated as mantra as it appears repeatedly on people’s Facebook walls and Twitter feeds.

Indeed, the more these claims get repeated and shared, the more likely it is to cause an availability cascade. 3 The availability cascade is effectively the result of a particular ‘factoid’ or ‘unfactoid’ going viral, and gaining significant social plausibility by the availability bias. The degree of sensationalism and clickbait present in our modern news media is just one example of this type of cascade.

Furthermore, if you are in an academic field like I am, don’t get all high and mighty over not falling prey to the availability bias. We have our own two special instances of it: the NAA and FUTON biases.  The NAA bias represents the ‘No Abstract Available’ condition, where articles have reduced citation and engagement rates if the abstract for the article is not publicly available. The FUTON bias is the reverse and finds that where the material is available as ‘Full Text On Net,’ i.e. open publishing or similar, the article is engaged with at a higher rate. As one Lancet study observed this leads to ‘concentrat[ing] on research published in journals that are available as full text on the internet, and ignor[ing] relevant studies that are not available in full text.’ 4

imagenoise_SIGNALmlab2What does this mean then? Well simply put it’s a question of Signal-to-Noise ratio. 5 If articles that propose some vague theory that sounds plausible but goes against the academic evidence are left to fester and be shared around, then they gain a veneer of plausibility. One such category of articles in my current field (theology) are the repeated ‘Jesus myth’ pieces that come out every Christmas, with predictable regularity. Such as this one from last year: http://theconversation.com/weighing-up-the-evidence-for-the-historical-jesus-35319 To maintain an appropriate SNR there needs to be appropriate responses to such articles, such as this one from John Dickson: http://www.abc.net.au/religion/articles/2014/12/24/4154120.htm Or take the claims of various health related article that are shared regularly around Facebook, these too need robust counter claims. Because unfortunately the ‘live and let live’ or the ‘sweep it under the rug and let it die’ approaches only allow the viewpoints to fester, and with enough availability (shares and reshares) they become plausible in the public sphere and consciousness.

So in short, even though simply repeating things ad infinitum or just yelling them louder should not work in the public square, it unfortunately does affect opinion and plausibility. As annoying, distasteful and time consuming as it may be, inaccurate claims need to be refuted, and done so on such a medium that it allows for such public availability. To simply ignore them reduces the signal-to-noise ratio and reinforces the availability bias.

Comment below and let me know of your applications of the availability bias, and even what other biases you would like me to look at. For those that have asked the Dunning-Kreuger effect is coming up soon.


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  1. Hasher, L., Goldstein, D., & Toppino, T. (1977). Frequency and the conference of referential validity. Journal of Verbal Learning and Verbal Behavior, 16, 107- 112.
  2. emph. mine
  3. Kuran, Timur and Sunstein, Cass R., Availability Cascades and Risk Regulation. Stanford Law Review, Vol. 51, No. 4, 1999; U of Chicago, Public Law Working Paper No. 181; U of Chicago Law & Economics, Olin Working Paper No. 384. Available at SSRN: http://ssrn.com/abstract=138144
  4. Wentz, R. (2002). “Visibility of research: FUTON bias”. The Lancet 360 (9341): 1256–1256.

    As a side note, this is one reason why many of the articles I refer to are behind pay walls. I deliberately choose non OA research, so perhaps I’m exhibiting the reverse FUTON bias.

  5. Yes! Finally some vague reference to my telecoms & radio background.