A new research at the University of Chicago said that the Rhesus monkeys use their own type of baby talk to interact with their infants, similar to human mothers.

The article, “Intended Receivers and Functional Significance of Grunt and Girney Vocalizations in Free-Ranging Rhesus Macaques” published in the current issue of the journal Ethology is based on the study conducted by the researchers on a group of free-ranging rhesus macaques, which live on an island off the coast of Puerto Rico.

“Motherese is a high pitched and musical form of speech, which may be biological in origin,” said Dario Maestripieri, Associate Professor in Comparative Human Development at the University. “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.”

Maestripieri and his team also said that the calls appear to be used to elicit infants’ attention and encourage their behavior. They also have the effect of increasing social tolerance in the mother and facilitating the interactions between females with babies in general.

Though, unlike human mothers, the rhesus macaque mothers did not direct grunts or girneys toward their own offspring. It could be that the monkey mothers are familiar with their own offspring and use the vocalizations with other babies because they are excited about the novelty of seeing a new infant, Maestripieri added.

Also, the researchers found that the use of these vocalizations is intended to facilitate the communication between the adult Rhesus females. When using “baby talk” the females indicate that they want to play with the infants and are unlikely to harm them, which is an indication for the infant’s mothers that everything is in order.  

Studying the noises made by the non-human primates is a important field of research for the scientists as they try to understand how they are used for communications.

Earlier this year, the Rhesus monkey was the second non-human primate to have its genome sequenced and the US scientists said they share a 97.5 percent genetic similarity with humans.