Differential sensitivity to conspecific and allospecific cues in chimpanzees and humans: a comparative eye-tracking study

Abstract

Previous studies have shown that a variety of animals including humans are sensitive to social cues from others and shift their attention to the same objects attended to by others. However, little is known about how animals process conspecifics' and another species' actions, although primates recognize conspecific faces better than those of another species. In this study, using unrestrained eye-tracking techniques, we first demonstrated that conspecific social cues modulated looking behaviours of chimpanzees more than human cues, whereas human observers were equally sensitive to both species. Additionally, first pass gaze duration at the face indicates that chimpanzees looked at the chimpanzees' face longer than the human face, suggesting that chimpanzees might extract more referential information from a conspecific face. These results also imply that a unique ability for extracting referential information from a variety of social objects has emerged during human evolution.

Figure 1.

Example of stimuli.

Figure 2.

Effect of social cues on looking duration in Look and Reach conditions. (a) Mean (+s.e.m.) looking duration of eight chimpanzees. (b) Mean (+s.e.m.) looking duration of eight humans. Post hoc t-test, *p < 0.05.