Nearly everyone who bends over the crib of a baby bursts into bubbling, musical tones to try to get the infant's attention. This baby talk, or “motherese,” is widely considered to be a universal feature of human language, but now scientists report that a similar phenomenon might exist in other species—a finding that could help explain baby talk's evolution.

Rhesus monkeys use special vocalizations called grunts and girneys when they are around infants, but most researchers had believed the monkeys were directing the sounds at the mothers holding the babies. Now University of Chicago biologists Dario Maestripieri and Jessica Whitham have shown in a careful observational study that the monkeys were aiming the soft, nasal sounds at the infants. The vocalizations, Maestripieri says, are probably intended to get the newborn's attention and facilitate social interactions among group members—some of the same functions baby talk is thought to serve in people.

This monkey version of baby talk lends support to the popular theory that motherese helps humans build connections with their infants by attracting and holding the babies’ attention. Some researchers believe that the interest babies show in motherese could aid language development, and a few linguists take the idea a step further, suggesting that the extended vowels and exaggerated tones of motherese could teach infants basic grammar. Others contend, however, that the melodic sounds may have a simpler purpose—to facilitate comprehension.

This hypothesis is supported by another new study, which showed that motherese can convey meaning between people who do not speak the same language. Cognitive psychologist Greg Bryant of the University of California, Los Angeles, found that the Shuar people of South America, who do not speak or understand English, were able to get the gist of North American mothers’ utterances 75 percent of the time when the women spoke as if they were addressing a newborn. This cross-cultural comprehension of motherese suggests that its basic characteristics appeared early in human history—and that it may have originated for the same socially beneficial reasons that led our monkey relatives to develop their own form of baby talk.