#30in30 – When Quantity beats Quality

The 30 in 30 Briefing Series focuses on a new cognitive bias, fallacy or heuristic in every single publication. By this Briefing we want to provide you with a rough overview on the cognitive theories most likely to occur in the legal profession. Today’s content: The Illusory Truth Effect.

The term was originally coined by Hasher, Goldstein and Toppino in 1977 though the existence of the phenomenon has been known for centuries. It is the tendency by which repeated exposure to information increases its perceived truthfulness, or in other words, people are prone to perceive pieces of information heard repeatedly to be more credible than new information. Surprisingly, prior knowledge of the actual truthfulness of the statement does not affect the effect, i.e. people will start disbelieving what they previously knew to be true.

Repetition has always been used as a means to drive a point home so to say. Students have of course always known this but so have politicians, statesmen, propagandists, the media, advertisers and authors.

For most people new information provided does not even need to reflect their own views or what they believe to be true. If repeated often enough information ingrains itself in the mind in such a way that people will, at the very least, second guess their initial beliefs.

Simple examples of this include hearing from numerous sources that a particular bar is supposed to be really good and when later being asked to recommend a place to go to, regardless of whether you have actually been there or not, being likely to mention that particular bar; or if you find raving reviews for a product online, you are more likely to consider buying that product regardless of whether you know it to be the same as any other.

The illusory truth effect has numerous effects in the legal field as well.

Consider a high-profile case that receives a lot of media coverage, facts get twisted and perceived law and morality get applied to these facts. People tend to start believing the view presented to them as being factual truth including those with actual knowledge of the relevant facts such as judges and jury members. Regardless of the requirement to consider nothing but the evidence, certain prejudices and perceptions have a risk of creeping in.

Lawyers are also far from immune to this effect. The more a lawyer gets involved in a case, the more confident he becomes in his argument and his case and it becomes difficult to take a step back and look at the arguments objectively.

Lawyers, if they suspect this is the case, may benefit from asking another member of the firm to evaluate how convincing their case actually is. Many law firms invest in internal mock trials to test precisely for this.

Legal professionals may also use this to their advantage. Constant repetition of their arguments and their view of the facts is more likely to make their argument more believable.


(Picture with courtesy of pixabay)