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Eva Maria Luëf and Katja Liebal of the Free University of Berlin have published in the American Journal of Primatology a new paper documenting the occurrence of motheresein 24 captive lowland gorillas.

Baby gorilla sleeping on his mother, by bartdubelaar

Baby gorilla sleeping on his mother, by bartdubelaar

During a 4 month observation of these gorillas, it was observed that elder gorillas used different gestures to start and stop play. To engage in play, the older gorillas would typically slapp others while making a “play face” or somersault. And to end play, these gorillas would place hand on the other gorilla’s head. But when engaged with infants, each older gorilla used repeated touch-based gestures more. As explained in the abstract,

Infant-directed speech is a linguistic phenomenon in which adults adapt their language when addressing infants in order to provide them with more salient linguistic information and aid them in language acquisition. Adult-directed language differs from infant-directed language in various aspects, including speech acoustics, syntax, and semantics. The existence of a “gestural motherese” in interaction with infants, demonstrates that not only spoken language but also nonvocal modes of communication can become adapted when infants are recipients. Rhesus macaques are so far the only nonhuman primates where a similar phenomenon to “motherese” has been discovered: the acoustic spectrum of a particular vocalization of adult females may be altered when the addressees are infants. The present paper describes how gorillas adjust their communicative strategies when directing intentional, nonvocal play signals at infants in the sense of a “nonvocal motherese.” Animals of ages above infancy use a higher rate of repetitions and sequences of the tactile sensory modality when negotiating play with infants. This indicates that gorillas employ a strategy of infant-specific communication.”

A video of this behavior is provided by the New Scientist.

I used to work with two gorillas who both extensively used gestures to relay communication. So, I assume all who have taken care of these great apes would appreciate that it is is vital for all gorilla infants to identify different signals, similar to how human infants gain expertise spoken (an non-spoken) language. In both great apes, simplifying these forms of communication into baby talk, and repeating possibly help in solidifying associations.

LUEF, E., & LIEBAL, K. (2012). Infant-Directed Communication in Lowland Gorillas (Gorilla gorilla): Do Older Animals Scaffold Communicative Competence in Infants? American Journal of Primatology DOI: 10.1002/ajp.22039

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