Mother Knows Worst: Abusive parenting spans generations in monkeys

It’s bad enough that some rhesus monkey mothers regularly kick, hit, bite, and otherwise brutalize their babies. But to make things worse, females exposed to such abuse as infants often grow up to become abusive parents themselves, perpetuating a primate cycle of family violence, a new study finds.

MOMMY DEAREST. Some rhesus monkeys brutalize their offspring. Here, an abusive mother appraises her child in a Puerto Rican animal preserve. Maestripieri

Being abused as an infant outweighs any primarily genetic trait, such as an anxious temperament, in fostering abusive parenting by female monkeys, says primatologist Dario Maestripieri of the University of Chicago.

His argument rests on two central observations. First, rhesus moms frequently mistreated their babies after having themselves been raised by abusive mothers, either biological or adoptive. Second, females born to abusive mothers uniformly became caring parents after having been raised by nonabusive adoptive mothers.

“Rhesus monkeys are an excellent animal model of human child abuse,” Maestripieri asserts. The ways in which these behaviors get transmitted across generations in monkeys and people “may be very similar,” he adds. In people, roughly 30 percent of abused children become abusive parents.

Maestripieri’s team worked with a population of rhesus monkeys living at an outdoor research facility in Georgia. The population included some females who had been observed to abuse their offspring. The researchers transferred some newborns between mothers to create four groups of female infants: six infants born to physically abusive mothers and given as newborns to unrelated, nonabusive mothers; eight infants born to nonabusive mothers and adopted as newborns by abusive mothers; eight infants born to abusive mothers and raised by them; and nine infants born to nonabusive mothers and raised by them.

The scientists tracked each infant into adulthood and observed her for 3 to 4 months after she gave birth to her first child.

Nine of the 16 females reared by abusive mothers—including 4 born to nonabusive females—abused their own offspring.

None of the 15 females reared by nonabusive mothers became an abusive parent. The Chicago scientist’s report appears in the July 5 Proceedings of the National Academy of Sciences.

These findings make “a strong case for nonhuman models of child abuse,” remarks psychologist Seth D. Pollak of the University of Wisconsin–Madison. However, researchers disagree about the extent to which abusive parenting in monkeys and people is similar (SN: 5/23/98, p. 324:

It’s “seldom possible” to consider monkeys’ social behavior as analogous to that of people, says primatologist William A. Mason of the University of California, Davis.

His view echoes that of two psychologists, Gilbert Gottlieb of the University of North Carolina at Chapel Hill and Robert Lickliter of Florida International University in Miami. They asserted in the May 2004 Social Development that because of developmental differences between species, monkey models at best provide “food for thought” about how human child abuse occurs.

Maestripieri disagrees. When scientists understand why some female monkeys repeat the cycle of child abuse with their own babies and those of others, they’ll be better prepared to come up with tests of prevention strategies that may be applicable to people, he says.

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.