Eye-tracking technology to study chimpanzee communication

I am a Post Doctorate researcher at the University of York. I study communication behaviour of chimpanzees. Like ourselves, chimpanzees use visual and vocal signals to communicate. I examine whether chimpanzees can identify their visual signals and if they know what each signal means.
I use a technology called eye-tracking. Eye-tracking uses a special camera to measure where the chimpanzees are looking. I show them pictures and videos on a computer screen, and the eye-tracker camera, which is placed below the screen, measures where and for how long the chimps are looking. At the Edinburgh Zoo, all research is completely voluntary; the chimps can come and go into the research area as they please. As a reward for participation, chimps get to drink their favourite fruit juice during the experiment.