Lowland gorillas converse with each other primarily through nonvocal gestures.

While researching how captive gorillas communicate during play, study leader Eva Maria Luef noticed that animals older than three years had a special way of interacting with younger gorillas. (See lowland gorilla pictures.)

With infants, the older gorillas used touch and repeated gestures—such as grabbing or stroking the infant's jaw—more frequently than they did when communicating with their peers.

"We were surprised that ... [gorilla] infants are addressed differently," said Luef, of the Department of Education and Psychology at Berlin's Freie University.

The behavior is evidence of a "gestural motherese," according to the study, published in June in the Journal of American Primatology.