How well can chimpanzees use the past decisions of other individuals to predict their future decisions? These are highly social animals, and competition and cooperation form an important part of their lives. If they can observe others’ actions and develop an understanding of their goals and preferences, this should help the chimpanzees to avoid unnecessary competition over resources. In cooperative interactions, it can help individuals to coordinate smoothly with one another.

In humans, our eyes demonstrate the manual actions we expect others to take. We spontaneously look at the object we think somebody is aiming for. A study conducted in 2014 showed that the same is true for chimpanzees. The chimps were shown videos of a human hand repeatedly reaching for and grasping one object and ignoring a second object. Then, two hands reached into the frame and swapped the locations of the two objects. In the test, the hand reached towards the objects and then paused. The researchers found that the chimpanzees looked proactively towards the same object that the hand had grasped before, rather than looking towards the location the hand had gone to before. This showed that they were rapidly predicting the hand’s behaviour based on the hand’s previous actions.

Here we are aiming to replicate the results of the 2014 study. We show the chimpanzees videos of a hand repeatedly grasping either a rubber duck or a plastic frog. We record their eye-movements with great precision using special eye-tracking technology. The question we are asking is, if a subject saw the hand repeatedly choosing the duck, then when the objects are switched, do they look towards the duck in expectation of the hand going to grasp it?

As well as videos with a human hand, we also show the chimpanzees videos of a plastic claw reaching for the objects. We are interested in whether they will find it harder to predict the behaviour of a plastic claw in comparison to a human hand.