This Inside Higher Ed article summarizes a study about the effects of racial and opinion diversity on people’s opinions about access to college. The "newsworthy" finding is that racial and ethnic diversity in a discussion group are more likely to lead to changes in opinions than is opinion diversity (which may not be manifested if the "outliers" don’t speak up). The study’s authors and the IHE reporter want the big takeaway to be that racial and ethnic diversity matter in education, and that, by itself, "mere" diversity of opinion doesn’t have the same sort of effect as the former sort of diversity. If you want to change people, change the complexion of those with whom they interact.
Well, I dunno. A one-time discussion isn’t a very good proxy for a classroom relationship that extends over a semester or a campus community that goes longer than that. People who are initially silent may gain the confidence to speak up over time.
Unless, perhaps, their opinions are clearly and consistently disfavored by the dominant (student, professorial, or administrative) voices. I’d be interested in a study of what it takes to get the silent to speak up.
Update: On reflection, there are all sorts of other things wrong with this study, at least as it’s reported. First, let’s raise the question of whether changing people’s opinions is, absent everything else, a good thing. If the opinions are bad, sure, but if not, why? Second, why not be open to the possibility that the result of exposure to "diversity," however understood, might be to confirm opinions? Openness to evidence and argument may produce confirmation rather than change. Third, the bare argument for intellectual diversity is almost (but not quite) as reductionist as the argument for racial and ethnic diversity. Proponents of the former who go no further assume a kind of intellectual and moral equivalence among arguments, leaving it to the "marketplace of ideas" to sort out quality. But absent considerations of quality, a diversity of arguments can’t be expected to produce anything good, especially if the folks who are supposed to sort them out aren’t all young Socrateses.
What this last consideration leads me to is not a simple-minded call for intellectual diversity in faculty hiring, but rather a call for faculty to be intellectually honest and even-handed, putting forth the best possible arguments for all positions, or perhaps even tilting against a classroom consensus to make students think their own positions through. This is good teaching, regardless of who the professor votes for in November.