Humans might not be the only species to go ga ga"" over their infants. A recent study published by University of Chicago researchers suggests female rhesus monkeys may also engage in a form of ""motherese,"" a form of baby talk in which parents make high-pitched cooing noises for their infants.
Though the female rhesus monkeys were not observed directing their baby talk to their own young, they made melodic purring sounds called girneys when near other baby monkeys.
Until recently, scientists interpreted the female monkeys' vocalizations as a way of signaling to the monkey mothers that they meant no harm to the baby. Researchers traditionally believed this communication to be vital, since scientists have witnessed temporary infant kidnappings and tug-of-wars over babies in several monkey species.
But University of Chicago researchers weren't convinced that the rhesus monkey girney calls were directed at the mothers. Jessica Whitham, a recent University of Chicago graduate, and Dario Maestripieri, associate professor of Comparative Human Development, teamed up with Caribbean Primate Research Center and spent two years observing 19 wild rhesus monkeys on a Puerto Rican island.
They found that while grunts and girneys were scarce before the birth season, they increased dramatically with the birth of new monkeys.
""The calls appear to be used to elicit infants' attention and encourage their behavior,"" the researchers wrote in the September issue of the journal Ethology. Rather than monkey moms feeling uptight, the scientists reported the female monkey's baby babble created a relaxed environment, where the baby was the center of attention.
UW-Madison psychology professor Charles Snowdon is not persuaded the girneys are only directed at the infants.
""Motherese is not just talking to babies but using a specific pattern of vocalizations to influence the baby's behavior,"" Snowdon said. He further explained that if monkey motherese was directed at the infants, one would expect to see an infant respond to the girneys. As Snowdon points out, the results of the University of Chicago study indicated that the infant responded less than one-third of the time to girneys directed at them.
Similarly, Snowdon suggested that even if the girneys were cooed toward the infant, the study doesn't indicate whether the mother was in hearing range, and therefore could be part of the intended audience. If the mother was within listening range, then this supports the possibility that the girneys could be similar to human interactions directed mostly at the mom, but delivered in high-pitched glissandos, such as the all-familiar, ""Oh, he's a wittle cutie! Can I hold him?""
Further research could help illuminate the purpose of the monkeys' grunts and girneys. Indeed, many studies of human motherese suggest that the intonations and pitches of the noises are universal and transcend cultural boundaries.
Perhaps we share these vocal
characteristics with our primate kin as well.
