Gay rights advocates often claim that pro-gay marriage court decisions increase public support for gay marriage through the "example effect" of giving heterosexuals an opportunity to observe happily married gay couples. People who see or better still, personally know, gays who benefit from being able to marry are likely to become more sympathetic to gay marriage than they were before. Since pro-gay marriage court decisions allow gays to marry in states where they would not be able to otherwise, they presumably contribute to opinion-altering example effects.

I think there is something to the example effect argument. But there is a reason why I didn't include it in my litany of reasons why pro-gay marriage court decisions help advance the cause of gay rights: I fear that the effect may be overblown.

Lots of surveys show that personal acquiantance with gays is correlated with support for gay marriage. For example, a recent Pew survey shows that 55% of those who have gay friends or relatives support gay marriage, compared to only 25% of those who don't. This data may support the example effect thesis. However, it is not clear which way the causation runs. It could be that heterosexuals who are already more tolerant are more likely to establish friendships with gays than those who are less so. Moreover, gays are more likely to "come out" to tolerant acquiantances than homophobic ones.

Other survey data suggest that the legalization of gay marriage in Massachusetts and Connecticut has not increased public support for it. Today, 55% of Americans oppose gay marriage and 36% support it, statistically identical to the 57-35 margin that existed in early 2001 (two years before the Massachusetts decision). There is, therefore, little evidence that the example effect of gay marriage has increased support for the practice, at least so far.

The history of interracial marriage, to which the gay marriage struggle is often analogized, is also a case in point. Interracial marriage was legal in many northern states throughout the Jim Crow era. Yet there is little if any evidence suggesting that this fact diminished public opposition to interracial marriage during most of that time. Jim Crow-era black public figures who married whites, such as Frederick Douglass and Jack Johnson, were widely reviled for doing so, sometimes even by other African-Americans. Their examples had little positive influence on public opinion.

More generally, the way one reacts to the existence of gay marriages depends in large part on one's preexisting views. A person supportive of gay rights is likely to applaud the sight of married gay couples. A homophobe is likely to to consider it offensive and perhaps become even more virulent in his opposition to the practice. This is part of the more general phenomenon that people tend to interpret new political information in ways that reinforce their preexisting views.

That said, it may be that example effects will influence public opinion in a pro-gay marriage direction in the long run. There is some evidence that support for gay marriage has increased in Massachusetts since the state instituted it in 2003, even if it hasn't had the same effect nationally. I doubt, however, that the effect will be as great as many people think.