Theory of Mind: What Do Chimps Know?

Theory of Mind refers to “the ability to ascribe internal states (such as beliefs, desires and knowledge) to others, especially when these internal states are different to our own.” Typically developed adults seem to have mastered this, although there is debate on how automatic, and how easily, adults can use it. There is also considerable debate about when Theory of Mind develops in adults, with some claiming the ability develops at around 5 years (Wellman, Cross & Watson, 2001), and others saying it develops as young as 15 months (Onishi & Baillargeon, 2005). That being said, the type of abilities shown by these two age groups are vastly different.

                As well as this debate within the field of Theory of Mind, another, equally interesting debate is taking place. That debate is whether these “higher cognitive functions” (Theory of Mind is an example of one of these) are unique to the human race, or whether other animals can also do these things. If these abilities are distinctly human, it could explain how we evolved. Great apes are considered the most likely to have these abilities, as they are the closest ancestors to us in the animal kingdom. A lot of research in this area has looked at whether chimpanzees have Theory of Mind.

                One particularly interesting study was conducted by Hare, Call, Agnetta and Tomasello (2000). They used the fact that chimpanzees have a dominate subordinate structure in wild packs to investigate chimpanzees Theory of Mind abilities. How this experiment worked, is two chimps (one dominant and one subordinate) where opposite each other in two separate corridors going into a big room. Two barriers where in the room, angled in a way that if the barrier was not clear only the subordinate chimp could see what was hidden behind the barrier. In half the conditions (control) the barrier was clear, so both chimps could see what was hidden behind. If the subordinate chimpanzee understands what the dominant chimpanzee can and cannot see they should go for the food more when it’s hidden from the dominant chimp than when it’s not. This was indeed the case.

                However, it is possible to argue that this is not showing a proper understanding of Theory of Mind, as the chimpanzees are not demonstrating an understanding of false beliefs, but instead demonstrating they understand what other chimpanzees can see. It has previously been shown that chimpanzees use posture and eye position to determine what others can see (Povinelli & Eddy, 1996). This however, has nothing to do with understanding mental states. Therefore, the Hare, Call & Tomasello (2001) study better demonstrates chimpanzees Theory of Mind abilities. The design was similar to the previous study, however the barriers where always solid colour. In both conditions, both chimps would see an experimenter hiding food behind one of the barriers. However, in one of the conditions, while the dominant chimp was distracted, the subordinate chimp saw the food being moved from the one barrier to behind the other. Therefore, if the subordinate understands others false beliefs, in the “misbelief” condition they should be more likely to go for the food, as they know the dominate chimp does not know where the food is. This is indeed what they found!

                These studies do seem to show, chimps have an understanding of Theory of Mind. However, it’s important to note that not everyone agrees that these studies show understanding of Theory of Mind. The trouble with looking at the higher cognitive functions of animals, is they cannot tell us what they are doing or thinking. We have to try and determine these things through the animal’s behaviour, and there is always a possibility they are using a different strategy to the one we think we are observing.

                There is a theory that Theory of Mind abilities come in two forms, an early developing form which is simplistic, and a more complex later developing ability. In my opinion, chimpanzees have the earlier developing form, but not the same complex abilities as normally developing adult humans.

                What do you guys think? Do chimps have a Theory of Mind? And if they do, what does this mean for humans?

References

Hare, B., Call, J., & Tomasello, M., (2001). Do chimpanzees know what conspecifics know and do not know? Animal Behaviour, 61, 139-151.

Hare, B., Call, J., Agnetta, B., & Tomasello, M., (2000). Chimpanzees know what conspecifics do and do not see. Animal Behaviour, 59, 771-785.

Onishi, K. H., & Baillargeon, R. (2005). Do 15-Month-Old Infants Understand False Beliefs? Science, 308(8), 255-258.

Povinelli, D.J. & Eddy, T.J. (1996) What Young Chimpanzees Know about Seeing. Monographs of the Society for Research in Child Development, Vol. 61, No. 3.

Wellman, H., Cross, D., & Watson, J. (2001). Meta-analysis of Theory of Mind Development: The Truth about False-Belief. Child Development, 72(3), 655-684.