Joint Attention in Wild Chimpanzees and Human Infants: a Comparative Approach

The ability to engage in joint attention is a pivotal milestone during human development. Whether this ability is uniquely human or shared with chimpanzees is hotly debated. Progress has been hampered by testing chimpanzees and humans with different methods, which has prevented meaningful species comparisons. In addition, little is known about cultural variation of joint attention in human infants and the socio-environmental factors linked to its development.
In order to address these issues, I applied a standard set of experiments to chimpanzee, Ugandan and British mother-offspring dyads in their natural environments. I presented a novel laser stimulus into the visual field of the offspring or an offspring-mother dyad and analysed the resulting behaviour and interactions.
In all three groups, offspring showed similarly low rates of laser-related communicative behaviours, when their mothers were inattentive and instead engaged with the laser individually. When the laser was visible to both the mother and offspring, however, humans engaged significantly more in joint attention than chimpanzees who only engaged in two instances of joint attention. Furthermore, human mothers of both cultures observed their infant’s interaction with the laser more and communicated more during mutual gaze than chimpanzee mothers, suggesting that mothers play an important role in scaffolding early joint attention interactions.
Socio-environmental factors that might explain this species difference were identified by collecting observational data on the participants’ everyday activities. Chimpanzee offspring vocalised less and spent less time engaged in activities that may promote joint attention (social activities, dyadic play, play with objects) than human infants. The offspring’s main social partner during everyday life activities did not, however, predict group-level joint attention performance. To conclude, the overall patterns of results of this thesis suggest joint attention skills are present in chimpanzees, but the motivation to engage in joint attention may be uniquely human.