CICASP | Center for International Collaboration and Advanced Studies in Primatology

This time of the year, if you are hiking on a snowy mountain and see what appears to be a Yeti walking towards you, you should probably be alarmed and call the appropriate authorities (sorry, PRI doesn't have Yeti experts!).

 

You—and we humans—have this ability to visually recognize humans versus non-humans because, in our heads, we have an 'image' of what a typical human body looks like. Dr. Gao Jie, a PRI alumna (and our former teaching colleague at CICASP) who is now a JSPS Postdoctoral Fellow, wants to know whether that's unique to humans. To answer that question, she studies one of our closest evolutioanry relatives, the chimpanzees. Her new paper on the subject was just published in the journal Animal Cognition, so we invited her to discuss her latest findings and, more generally, what it's like to study chimpanzees at PRI.

 

 

Gao: In my article, what I mean by "body representations" is basically visual representations of bodies. In humans, for example, we can discriminate whether an animal is a human or a non-human animal, based mainly on visual cues. We use bodies to do everything, including social communication. We have pointing gestures to deliver information, and other bodily gestures to express intentions and emotions.

The understanding of what typical bodies look like is important for our daily life. Also, when a body looks strange, it might show injury and the need for medical care. In humans, we have this body representation. Bodies convey a lot of social information for chimpanzees, too, and they also use visual cues extensively. My colleagues and I wondered if chimpanzees also had body representations of chimpanzee bodies. Studying chimpanzees will also help shed light on the evolution of visual representations of bodies.

Gao: I think using traditional methods—such as face-to-face experiments, or touchscreen cognitive tasks—can tackle this topic as well, but indirectly. For example, we can test chimpanzees' reactions to atypical bodies, but it won't be that direct and accurate, compared to the eye-tracking method we used in this study: we could know where exactly they were looking at, when presented with various bodies. Another difficulty is that many previous studies have touched this topic, but there were too many cognitive processes at play—like imitation tasks using bodily gesture—so it was difficult to know exactly how they represent bodies.

 

Eye-tracking techniques help a lot in this topic. It enabled us to see where chimpanzees' gazes were and how long they looked at each place. We could examine their attention to various body pictures and know whether they paid special attention to strange body parts or not.

Gao: With 480 trials involving 6 chimpanzees, it took me several months to complete the task. One thing I did not expect was that the chimpanzees looked at other places instead of the screen during the task...so we covered the setting with a black cloth. It still happened, but it was somehow normal in chimpanzees. Their gaze is faster than humans, so they probably lose interest for the pictures after some time.

Gao: Not really. Chimpanzees can discriminate themselves from other animals, and they showed some evidence of body representation in my previous experiments examining body perception, so in theory it was expected that they notice the strange parts on chimpanzee bodies. 

Gao: I think the human part might be easier for them to detect, because the fundamental looks are different from chimpanzee body parts as well (e.g., they are smooth). Still, they showed a tendency to look longer towards the misplaced arms and legs [image B in the figure above], compared to control, suggesting they might know that they are strange. We may need to conduct more trials to test this futher.