"The amazing thing is that the guys are always split 50-50. Age and income groups don't seem to matter," said Lisa Hayward, a UW doctoral student in biology and lead author of a paper reporting the findings in the current issue of the journal Evolution and Human Behavior.
The survey showed just 32 percent of women favor such routine testing. The difference in response between genders remained consistent in spite of marital and income status.
Previous studies have shown that generally less that 1 percent of married women bear children fathered by men other than their husbands. The exceptions are studies conducted among women living in extreme poverty in the United States, Mexico and England, where the rate was as high as 10 percent.
Researchers have speculated about why a woman would seek a father for her child other than her husband and often conclude that it is to improve the child's genetic heritage or to gain parental investment from more than one male. Either way, it would normally be advantageous for the woman to keep the child's paternity a secret so that her husband would continue to care for the child as if he were the father.
"There's this fascinating aspect that when we ask the guys who do not favor paternity testing why they are opposed, more than half of them say, 'Ignorance is bliss,'" said co-author Sievert Rohwer, a UW biology professor. "Then the question becomes, 'Whose ignorance, the cuckolder or the person being cuckolded?'"
Rohwer said the researchers speculate that few men are likely to father offspring with women to whom they are not married.
"Men who are successful as philanderers probably are rare, but they may be successful with many women," he said.
Rohwer for several years has, at the beginning of the fall quarter, asked students in a freshman-level and a senior-level biology class whether they would favor routine paternity testing when a baby is born. The answers were very similar year after year, he said, but those results were never formally compiled for research purposes.
While working as a teaching assistant in Rohwer's class, Hayward agreed to compile the results into a research paper. Surveys were given to 733 adults, 655 of them students enrolled in science classes at the UW or at Highline Community College in Des Moines, Wash. Of those responding, 294 were men and 439 were women. To broaden the range of ages and backgrounds, surveys also were completed by 78 adults outside a Washington state driver's licensing office and at Seattle-Tacoma International Airport.
Four different versions of the survey were used. For one version, 170 people were asked only one question: whether hospitals should routinely include paternity testing for newborns. The rest received a survey with two additional questions – one regarding a father's presence in the delivery room and the other regarding inducement of labor – to mask the real aim of the survey. The order in which the questions were asked was changed randomly.
"It comes out pretty much the same, whether you ask it by itself or ask it in the context of other questions, and no matter what order the questions are in," Rohwer said.
Smaller groups of those surveyed were questioned further about their responses. A high number of women who favored routine paternity testing said they wanted to reassure their husbands of their faithfulness, he said, and some wanted to make sure that, for health reasons, their children had correct information about their genetic heritage.
Of the men who favored testing, it was unclear just how strongly they were in favor of finding out their children's paternity. Rohwer said he hopes to conduct further surveys to determine the strength of that desire.
"There's a huge cost to finding out because there's all this mistrust that comes in," he said. "It has the potential to break up families and may not be in the male's best interest."
Evolution and Human Behavior