Newswise — Both chronically jealous men and women show less interest in infants and decreased happiness upon receiving pregnancy news. But jealous women show a higher level of “parental investment” in a child than do jealous men.

That’s what researchers at Texas Christian University in Fort Worth found in a series of experiments. “Across three experiments we found that jealousy plays an important role in men’s and women’s parenting interest and in their decisions to be emotionally invested in a child,” says Sarah E. Hill, assistant professor of psychology at TCU, who conducted the research with Danielle J. DelPriore, also of TCU’s psychology department.

The three experiments, conducted via questionnaires of university students, were designed to explore the relationship between jealousy and men’s and women’s desire to start a family and invest in children.

The first study showed that the threat of infidelity led chronically jealous men and women to show a decreased interest in infants. The second experiment indicated than both chronically jealous women and men were less happy upon receiving pregnancy news. The third study found that chronically jealous men felt less inclined to invest themselves in caring for and interacting with a baby. That was not true for women, however.

“From an evolutionary perspective, infidelity is as costly as it is psychologically painful,” says Dr. Hill. “This cost is particularly pronounced in the context of pregnancy and child rearing. For men, infidelity on the part of their partner opens up the possibility that they are not the biological father. For women, an unfaithful partner increases the likelihood of losing critical male resource investment.”

The first study employed the “interest in infants inventory,” a tool measuring reproductive readiness. About 120 persons, with slightly more women than men, were tested. Measures of relationship jealousy were also employed and 58 were determined to be jealous. Both jealous men and jealous women reported less interest in infants than the others.

For the second test, 108 students were surveyed, 56 in a jealous condition. All respondents were asked to imagine that they and their romantic partner were expecting their first child. They were then asked to rate on a nine-point scale how happy they would be upon receiving this news. “As predicted, people high in chronic jealousy showed diminished happiness about the news that they and their partner were expecting,” Dr. Hill reports.

Using the same procedures and controls employed in the first two studies the researchers, for the third experiment, asked 117 participants (55 in a jealousy condition) how much time they would ideally spend performing 22 duties related to childcare. These duties included holding the child and reading to the child.

“For women, jealousy had no effect on their desire to invest in children,” states Dr. Hill. “This result is consistent with the evolutionary logic of our model. For women, paternity is always certain. Among chronically jealous men, however, the threat of infidelity resulted in a diminished desire to invest effort in the love and care of an unborn child.”

Evolutionary psychologists theorize that the emotion of jealousy may be an adaptation shaped by natural selection to limit, for humans, the damage that can be done by infidelity. It may inhibit men from investing in biologically unrelated offspring. For women it may circumvent the loss of a male’s resource investment in her and her offspring.

Hill and DelPriore say that one of the limitations of the research is that it relied on self-report questionnaires rather than on capturing behavioral measures. “Future research on overt behavior is an important next step,” they say.

Their paper, “(Not) Bringing Up Baby: The Effect of Jealousy on Men’s and Women’s Parenting Interest and Investment Expectations,” is published in the February 2013 issue of the Personality and Social Psychology Bulletin.

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Personality and Social Psychology Bulletin (February 2013)