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Simple Jury Persuasion: The weaker the evidence, the more precise you become

Wednesday, February 19, 2014
posted by Rita Handrich

precise evidenceWhen your evidence is weak, how can you be more persuasive? Precision. Observers want to see certain things to have confidence in what you are saying. The more precise you are, the more likely the observer is to see you as knowledgeable and accurate (even when negotiating for salary!). So what does the observer look for to assess your confidence? For eyewitnesses, the researchers say, observers (such as jurors) rely on speech rate, eye gaze, posture, and use of nervous gestures to assess accuracy. There is a longing for certainty that draws people to rely on these cues even when they are told of the gap between eyewitness accounts and actual accuracy. More recent research has focused on the use of precision to elicit confidence in you from the observer. 

The researchers conducted two separate experiments: one with the ubiquitous undergraduate (N = 187) and one with Mechanical Turk (online research) participants (N = 163).

The undergraduates read answers to questions about the lengths of rivers and the heights of mountains (which had ostensibly provided earlier by other participants. They were asked to indicate their belief in the accuracy of the answers. The manipulation by the researchers was that the answers were presented as either “imprecise” (rounded to the 100s, e.g., 2600 miles) or “precise” (rounded to the first place, e.g., 2611 miles). The undergraduates were more confident in the “precise” answers to the questions.

The Mechanical Turk participants played a game akin to “The Price is Right” game show. The participants were asked to price three different products and were given help in the form of “audience suggestions”. The audience suggestions either ended with a 0 (imprecise) or ended with a 1 through a 9 (precise). Half the subjects were given estimates over the true value and half were given estimates under the true value. Then they were asked to “choose” the audience member who would “advise” them in the upcoming round of the game. The Mechanical Turk participants were more likely to choose an “advisor” who had provided a precise number (i.e., a number ending in 1 through 9).

Both undergraduates and Mechanical Turk participants believed more precise estimates were made by more confident (and likely more accurate) people. There is no real truth to this belief, but there you have it. If you are more precise, people think you are more confident and therefore are more likely to believe what you are saying. The authors use the example of “sports pundits often discuss[ing] National Football League draft prospects to hundredths of milliseconds–more precision than measurement error allows for”. People prefer precise estimates, say the researchers, “which creates incentives for such overprecise and misleading reporting”.

From a litigation advocacy perspective, the weaker your evidence, the more precise you want to be in identifying damages, settlement requests, or life care amounts. An example is to establish the amount of a life care plan to the penny, even though it is a projection and by its nature, imprecise.

“The weaker the data available upon which to base one’s conclusion, the greater the precision which should be quoted in order to give the data authenticity.” Norman Ralph Augustine

Jerez-Fernandez A, Angulo AN, & Oppenheimer DM (2014). Show me the numbers: precision as a cue to others’ confidence. Psychological Science, 25 (2), 633-5 PMID: 24317423


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