Tuesday, July 17, 2007

Empirical Evidence That Diversity Matters

We like to assume that a diversity has value, but is there any empirical evidence that a diverse group will make a better decision? The Scientific American blog discusses a jury experiment that offers empirical evidence that diversity does matter:

Many liberals share the vague intuition that a racially diverse (or representative) jury is "better" than a racially homogeneous one. The arguments for this view tend to be murky, though. Who benefits, and how, from racial diversity in the jury box? In a recent paper in Psychological Science [pdf download ], Tufts University psychology professor Samuel Sommers argues that this is an empirical question, and he provides a surprisingly powerful answer: when making a complex, ambiguous decision, everyone in a diverse group benefits.

. . .

In the study, Sommers asked 30 different mock juries, each composed of six adults, to watch a video summary, edited from Court TV coverage, of the trial proceedings of an actual sexual assault case in which a black male defendant allegedly assaulted, separately, two white females. Sommers went to extraordinary lengths to make these mock trials as much like a real trial as possible. The study was conducted in a courthouse. Participants were jury-eligible adults who were at the court for real jury duty. Their age ranged from 18 to 78. Only racial composition was varied systematically: half of the juries were white, and the other half were made up of four white and two black jurors.

The facts of the case were disputed and required jury deliberation. For example, one of the victims described a scar that matched a scar on the defendant's torso, but neither victim recognized his face; semen and hair left on the victim provided evidence that was consistent with the defendant's but not a definitive match.

In the end, the majority (55 percent) of the mock juries voted unanimously to acquit, just as the real jury had. But both verdicts and deliberation quality and content varied significantly depending on the juries' racial make-up.

Mixed and all-white juries were equally likely to raise the subject of race when discussing the case -- but differed sharply in how they reacted to the subject once it was raised. Every time racism was mentioned in an all-white jury, at least one juror objected that racism was not relevant (J5: "What about the fact that he was a Black man?" J6: "What does that have to do with it?"). That's a 100 percent rate of objection to the idea that race was relevant. In the diverse juries, by contrast, only 22 percent of mentions of possible racism met with objections. Meanwhile, the diverse juries deliberated longer, cited more case-relevant facts during deliberation, made fewer factual mistakes, and were more likely to correct inaccurate statements than the all-white juries were.

So who among the jurors is creating the difference in dynamics between the homogenous and heterogeneous juries? One possibility is that the black jurors alone improved jury performance. Black jurors may have different life experiences that lead them to contribute unique information and perspectives to the deliberations. By this hypothesis, it is the sole burden of the black jurors to provide the benefits of diversity.

But Sommers' data tell a very different story: He found that white jurors were actually responsible for a large proportion of the group differences, as they behaved differently in a racially mixed jury than in one all-white. White jurors in diverse groups mentioned more facts, made fewer factual errors, corrected more mistakes and raised the possibility of racism more often than did white jurors in homogeneous groups. Even before the deliberations began, white participants who expected to deliberate with black jurors privately espoused less harsh views of the (black) defendant than did white participants who expected to deliberate in an all-white group. Both the anticipation and the experience of serving on a diverse jury seemed to sharpen the white jurors' sensitivity not just to race but to accuracy and due process.

. . .

In all, Sommers' data show that diverse juries reason better, not just as groups but as individuals; everyone on the jury benefits, and justice, it appears, is better served. As Sommers concludes, these results make the benefits of diverse juries not just more concrete but readily attained. Minority jurors need feel no burden or need to "educate" white jurors or convey a unique minority perspective; diversity seems to do its own work. The results suggest that representative juries do not merely honor a civil right or a constitutional ideal but provide an effective tool for achieving more thorough and competent jury deliberations.

Read it all here.

Read the Sommers paper here.

This is very interesting--and it would be interesting to test this hypothesis with other decision making experiments.

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