Justice Martha B. Sosman of the state Supreme Judicial Court raised the research flag first.
In her dissent to the court's controversial ruling in support of gay marriage in November, she criticized her fellow justices for ignoring the scientific research on the subject of children, declaring, ". . . Studies to date reveal that there are still some observable differences between children raised by opposite-sex couples and children raised by same-sex couples."
Two months later, Focus on The Family, a nonprofit family education group with close ties to evangelical Christianity, responded to the court's ruling with a full-page newspaper advertisement stating that studies show that children are more likely to be suspended from school, have emotional problems and take drugs when raised by a single parent instead of both biological ones.
Now, with the state Legislature planning to reconvene a constitutional convention on gay marriage Thursday, others also are turning to science for answers.
They are not likely to find them. Virtually all the nearly 50 studies on the children of gay and lesbian parents -- who number between 6 and 14 million in the United States, according to various studies -- have found no significant differences between children raised by heterosexual or homosexual parents.
But most of the studies have been small and some of them solicited families through gay literature or participant referrals, rather than a more representative process. Critics, mostly opponents of gay marriage, charge they are methodologically flawed and, in some cases, politically biased.
"Those current studies that appear to indicate neutral to favorable results from homosexual parenting have critical flaws," according to the American College of Pediatricians, an advocacy group that opposes gay marriage.
Even veteran researchers concede that the field is in its infancy.
"We all interpret the data to the best of our ability and some of us may come up with different interpretations," said Charlotte J. Patterson, a psychology professor at the University of Virginia and one of the most prominent researchers in the field. "What we need is more good research."
Part of the difficulty is isolating exactly what factors influence a child's development. And there has been insufficient funding available to launch the kind of full-scale national study that many researchers believe is necessary to draw firm conclusions.
One study of families that have gone through divorces found that children of lesbian mothers were more likely to have had recent contact with their fathers than were children of heterosexual mothers. But another found no such difference.
One of the earliest studies found no difference when comparing 56 children of lesbians with 48 children of heterosexual mothers in terms of favorite television programs and favorite games, although the lesbian mothers were more likely than the heterosexual mothers to report that their daughters played with "masculine" toys such as trucks or guns. In a host of studies, most offspring of gay parents identified as heterosexuals. In one survey of 36 teenagers, for example, half of whom had lesbian mothers and half of whom had heterosexual mothers, no children of the lesbians identified as homosexual, while one child of a heterosexual mother did.
Patterson said that, while each study can be criticized, taken as a whole the studies point to a scientifically valid conclusion: Being raised by gay or lesbian parents does not make a child substantially different from his or her peers.
"In the long run, it is not the results obtained from any one specific sample, but the accumulation of findings from many different samples that will be most meaningful," Patterson wrote in one study. She added in a recent interview: "The point is that the studies yield the same results over and over."
It is precisely that consistency that piqued the interest of sociologist Judith Stacey of New York University. To Stacey, it didn't make sense that children raised in somewhat different circumstances would be exactly the same -- findings of "no difference, no difference, no difference, just seemed so implausible," she said. So, she began looking carefully at the existing studies.
In 2001, Stacey and her colleague, Timothy Biblarz, then both at the University of Southern California, published a review of the social science research, stating that not only had researchers actually found some intriguing differences but that they had lowballed them for fear of how the findings would be used.
While the pair did not find gay and lesbian parenting to be harmful to children, they concluded that there is reason to believe that the children of gay parents "do differ in modest and interesting ways from children with heterosexual parents."
For example, in a small but long-running study that followed the children of lesbians into young adulthood, Susan Golombok, a professor of psychology at City University in London, concluded that having homosexual parents did not encourage children to become homosexuals. But Stacey said she downplayed an interesting finding: The daughters of the lesbians were more open to the idea of being attracted to someone of the same gender than the daughters of the heterosexual mothers.
In addition, while none of the children of the 21 heterosexual mothers in the study had had a same-sex sexual relationship, six of the children of the 25 lesbians had had a relationship with someone of the same gender.
Golombok responded to Stacey's assesment in a recent study, but declined to be interviewed at greater length. Golombok wrote that Stacey and Biblarz have "overemphasized" the differences, and failed to distinguish between children's attitudes, which can change, and gender identity, which is relatively fixed. Only two of the children of lesbian mothers, and none of the children of heterosexual mothers identified themselves as gay.
Stacey said it is better to acknowledge possible differences than to publish studies that are misleading.
"Times have changed and it is no longer a particularly interesting or valuable story to emphasize no differences," said Stacey, who supports the granting of legal rights to gay parents. "The time has come to move on to more sophisticated research.
"Or at least it seemed to be until gay marriage came up," she said. "There is a lot of anxiety now. People may not want to wander into that storm."