In his study, he reported that, "Infant abuse in monkeys shares several similarities with child abuse in humans." Those similarities included how common it was in the population and the relationship between age and vulnerability to abuse. "About five to ten percent of all infants that are born every year are physically abused by their mothers," he says.
Although his study was on captive Rhesus monkeys, Maestripieri reported that similar abuse rates had been seen in these monkeys in the wild.
Maestripieri has been studying abuse in monkeys for 15 years. As he watched them at the Yerkes National Primate Research Center at Emory University, he saw that abuse, "seemed to be common in certain families." He combed the center's records for more than 4000 monkeys and discovered abuse, "was only present in certain families and never in others. And so, that suggested that it might be transmitted across generations."
The question was, is this learned behavior, or something in genes of just those monkeys? "We had identified some abusive mothers," says Maestripieri, "then we identified some mothers who had never abused mothers before." He says the research involved several groups of monkeys. With one, "infants were swapped at birth between these abusive and non-abusive mothers. And we also had two other control groups of mothers, both abusive and non-abusive who were allowed to keep their own infants and rear their infants."
This research was published in the July 5, 2005 issue of the Proceedings of the National Academy of Sciences and funded by the Harry Frank Guggenheim Foundation and the National Institutes of Health.