Facial expressions modulate the ontogenetic trajectory of gaze-following among monkeys.
Gaze-following, the tendency to direct one's attention to locations looked at by others, is a crucial aspect of social cognition in human and nonhuman primates. Whereas the development of gaze-following has been intensely studied in human infants, its early ontogeny in nonhuman primates has received little attention. Combining longitudinal and cross-sectional observational data from Barbary macaques at 'La Forêt des Singes', we show here that gaze-following among conspecifics develops within the first year of life with a rapid increase between 5 and 6 months, reaching adult levels at 1 year. Sex, rank, and relatedness of the animal whose gaze the subject followed did not affect gaze-following rates. Interestingly, however, the behavior was enhanced in all age classes if a gaze-cue was accompanied by a facial expression. Furthermore, the effect of facial expressions had a modulatory influence on the ontogenetic trajectory of gaze-following, suggesting that it is of functional significance in the development of the behavior. Follow-up analyses revealed that one specific facial expression that is given in response to social interactions between third parties was particularly efficient in eliciting gaze-following responses, indicating the importance of cues that are able to guide the acquisition of social information. Taken together, these results suggest that the development and the operation of gaze-following are tuned to the social and physical characteristics of a species' environment.
Brain Mapping Unit, Behavioural and Clinical Neuroscience Institute, Department of Psychiatry, University of Cambridge, UK.
Christoph
C
Teufel
Anke
A
Gutmann
Ralph
R
Pirow
Julia
J
Fischer
D000367:Age Factors; D000818:Animals; D000836:Animals, Zoo; D001288:Attention; D003071:Cognition / Q000502:physiology*; D005149:Facial Expression; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology*; D005602:France; D006608:Hierarchy, Social; D008251:Macaca / Q000502:physiology*; D008297:Male; D012737:Sex Factors