Rhesus monkeys with babies: Photo by jasmic at FlickrNew research at the University of Chicago shows that female rhesus macaques (also called rhesus monkeys) use special vocalizations when interacting with infants, in much the same way humans use motherese with human babies.

“Motherese is a high pitched and musical form of speech, which may be biological in origin,” said Dario Maestripieri, researcher and Associate Professor in Comparative Human Development. “The acoustic structure of particular monkey vocalizations called girneys may be adaptively designed to attract young infants and engage their attention, similar to how the acoustic structure of human motherese, or baby talk, allows adults to visually or socially engage with infants.”

In their study they noted that when a baby rhesus strayed away from its mother, the other female members would look at the baby and make vocalizations.

"Adult females become highly aroused while observing the infants of other group members," said Jessica Whitham, the study’s lead author and a recent Ph.D. graduate at U of C.

The “baby-talk” seems to draw the infant monkeys’ attention and encourage their behavior, and at the same time increase the social acceptance of the mother and her interaction with other females who have babies.

Monkey vocalizations can either carry information, such as warnings of approaching threats, or carry no information and just be noises from which the recipient can draw inferences. A good example would be the sound of a human sneeze. It can be inferred by us as being linked to the common cold, although it didn’t develop through evolution to send that information.

The Maestripieri team’s article entitled “Intended Receivers and Functional Significance of Grunt and Girney Vocalizations in Free-Ranging Rhesus Macaques” appears in the current issue of the journal Ethology, and shows that the grunts and girneys of the rhesus monkeys studied were not meant to send specific information, but rather were used to draw the attention of other individuals or to change their emotional states. The vocalizations to infants appear to not only grab the infant’s attention, but also infer that they only want to play with the infant, as well as sooth any concerns the mother may have that their babies were in danger.

The researchers also noted that the grunts and girneys were sometimes followed by an approach and grooming of the mothers.

Oddly, the team discovered that the rhesus mothers didn’t direct girneys or grunts toward their own infants, probably because they were used to them and were excited at the prospect of seeing a new infant in their midst.

LINKS

”Ethology” definition
Biology-blog.com story
World Science website story

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