By Brad Bell
Imagine that you are juror in a criminal trial in which the defendant is accused of stealing a duffle bag from a gym. One eyewitness is positive that the defendant took the bag, and the other eyewitness is positive that someone else took the bag. The eyewitness for the prosecution was much more detailed in her testimony. She described minor details, such as the can of Pepsi the culprit was drinking before taking the duffle bag. Would you be influenced by the trivial details in the eyewitness testimony?
In their second experiment, Bell and Loftus (1989) had college students read a brief summary of a criminal court case with conflicting testimony. The prosecution eyewitness stated that defendant was the person who committed the crime, and the defense eyewitness stated that the defendant was not the culprit. The defense eyewitness testimony varied in degree of detail. In a low detail version, the defense eyewitness described the store items that the culprit dropped as just “a few store items.” In the high detail version, the defense eyewitness described the store items as “a box of Milk Duds and a can of Diet Pepsi.” The prosecution eyewitness described the store items as just “a few store items.” However, there were two versions for the prosecution eyewitness testimony, In one version the prosecution eyewitness is not asked whether she can remember the store items mentioned by the defense eyewitness. In the other version, she is asked if she can remember the store items, and she states that she cannot remember them. When the prosecution eyewitness was not asked about the store items, there was no statistically significant effect of the trivial details on judgments of the defendant’s guilt. In contrast, when mock jurors learned that the prosecution eyewitness could not remember the store items, there was a substantial effect of defense eyewitness detail on judgments of the defendant’s guilt. When the prosecution eyewitness stated that she could not remember the store items, 6% rendered a guilty verdict in the high detail condition, and 47% rendered a guilty verdict in the low detail condition! The persuasive impact of trivial details was referred to as trivial persuasion by Bell and Loftus.
The findings from the second experiment conducted by Bell and Loftus (1989) suggest that the impact of trivial details on judgment of guilt is due to inferences about memory. The detail in the defense eyewitness testimony only influenced judgments of guilt when it was clear that the prosecution eyewitness could not remember the trivial details. In this situation, the mock jurors may have been more likely to believe that the defense eyewitness had a better memory for the culprit’s face than the prosecution eyewitness. Moreover, the defense eyewitness was judged to have a better memory for the culprit’s face in the high detail condition than in the low detail condition.
Even details that are unrelated to the crime may be persuasive. In their first experiment, Bell and Loftus (1989) found that unrelated details in the prosecution eyewitness testimony influences judgments of a defendant’s guilt. The details pertained to the store items that a customer dropped prior to the crime. It should be pointed out that some studies have not found trivial details to
be persuasive. Some findings for the influence of details were not statistically significant. For example, Bell and Jones (1994) found that the effects of minor details on judgments of honesty were not statistically significant in four studies.
Trivial persuasion may reflect a faulty belief about eyewitness testimony. Reporting trivial details may not indicate that a person has a good memory for a culprit’s face. For example, Wells and Leippe (1981) found that people who made an accurate identification of a culprit were less accurate in their memory for peripheral details.
Although trivial details may influence judgments in some situations, more research is needed to gain a better understanding of the influence of trivial details. It’s possible that trivial details may be persuasive in other contexts besides the courtroom.
References
Bell, B. E., & Loftus, E. F. (1989). Trivial persuasion in the courtroom:
The power of (a few) minor details. Journal of Personality and
Social Psychology, 56, 669-679.
Bell, B. E., & Jones, J. B. (1994). Providing minor details and the
perception of honesty: Questioning the generality of trivial
persuasion. Psychology: A Journal of Human Behavior, 31, 26-29.
Wells, G. L., & Leippe, M. R. (1981). How do triers of fact infer
the accuracy of eyewitness identifications? Using memory for
peripheral detail can be misleading. Journal of Applied Psychology,
66, 682-687.