Gorilla study hints at origin of human speech

A new study provides evidence that gorilla communication is linked to the left hemisphere of the brain - just as it is in humans.

Studying non-verbal communication of gorillas could be useful for human language impairments

Psychologist Dr Gillian Sebestyen Forrester, of the University of Sussex, developed a new method of analysing the behaviour of gorillas in captivity and found there was a right-handed bias for actions that also involved head and mouth movements. The right side of the body is controlled by the left hemisphere of the brain, which is also the location for language development.

The findings could provide major clues as to how language developed in humans. Dr Sebestyen Forrester said: “We shared 23 million years of evolution with great apes and then diverged approximately six million years ago. Gorillas have highly-complex forms of non-verbal communication. I think we are looking back at what sort of communication skills we may have once had.”

Previous studies by other researchers have found that chimpanzees show a right-handed preference for manual tasks. But Dr Sebestyn Forrester's research is the first to indicate a link between right-handedness and communication in apes.

The key to her findings, published Animal Behaviour, is the development of a detailed method for observing animals. “I have moved away from just studying visual communication signals of gorillas to looking for a method to capture code and analyse these signals,” she said. “For example, instead of subjectively labelling a behaviour as aggressive, I break down the behaviour into a sequence of stages based on eye gaze, facial expression and physical action. And I look for recurrent patterns within social context.”

The method - known as multidimensional method (MDM) - can also be used to study other non-verbal groups. Dr Forrester is now piloting a study of children aged between two and four years with language impairments. “Data from this method could help us to better understand the nonverbal communication signals that were important for the evolution of language and are still necessary for the development of normal language skills,” she said.