Chimpanzees have brains. Do they have minds? We don’t know. Yet


Science | by Greg Beatty

Jane Goodall made headlines when she compared Republican presidential candidate Donald Trump to a male chimpanzee engaging in all sorts fear/threat to establish dominance. The comparison seemed perhaps a little extreme (or not, if you watched his first debate with Clinton), but chimpanzees are our closest primate relatives, and researchers in many fields are exploring parallels between humans and chimps.

At the University of Saskatchewan, for instance, psychologist Carla Krachun is researching whether chimpanzees, like humans, possess “Theory of Mind”. I recently talked to her about her work.

What is theory of mind exactly?

Very simply, it’s the ability to think about what others are thinking. It’s something humans take for granted because it comes naturally to us. We go through our days making inferences about what those around us are perceiving and feeling, what their intentions are, what they know or don’t know, what they believe, and so on. The question is, is this is a uniquely human ability — or do our closest living relatives also have it, and if so, to what extent?

We share a similar brain structure to higher mammals but we have capabilities they lack. Is one goal of your research to determine how theory of mind is generated?

Our brains are similar in structure to other mammals, especially chimpanzees. However, they’re larger for our body size, and our prefrontal cortex is expanded relative to the rest of the brain. There are also differences in structure and connectivity. But it’s difficult to know which differences are most relevant to the human ability to conceive of the mind and reason about other minds. Largely, that’s because we don’t yet have a good handle on how the human brain creates what we call the mind.

All my research with chimpanzees has been behavioral. But in humans, some exciting research is being done with brain imaging. This research shows that two regions of the brain consistently become activated when people think about others’ mental states: the prefrontal cortex, and another area just above and behind our ears. Doing imaging work with apes, though, is more challenging.

Research with human children suggests the capacity for language, and our fundamental desire to share our mental experiences with others, may play a large role in theory of mind. Most people would agree that chimpanzees subjectively experience the world around them, and you can call that a mind. But we want to know if chimpanzees have a concept of the mind or think about others’ mental states. Finding evidence of theory of mind in a non-linguistic species would suggest that while language may assist in the development of advanced theory of mind, it may not be necessary for some simpler mentalizing abilities.

Is there a danger, when observing and interpreting chimpanzee behavior, of inferring human motives that maybe aren’t warranted?

There’s definitely a danger of reading too much into the apes’ behaviour — in fact, it’s a big source of disagreement among researchers. Somebody will say they’ve found convincing evidence of mentalizing in apes, and others will then argue for alternative ways of explaining the data. There are even terms for both sides: “boosters” and “scoffers.”

If we are going to get at the truth, we need to keep an open mind and not get too attached to what we would like to find. My own feeling is that there is research that strongly suggests apes have some mentalizing capacities, and behaviour observed by primatologists in the wild also suggests this. The major problem, even in the well-controlled lab environment, is it’s just too difficult to rule out the possibility that apes are simply responding to others’ behaviours without making any inferences about what’s going on in their minds, or that they’re acting on learned relationships between other environmental cues and particular outcomes. It’s a huge challenge to try to devise procedures that eliminate alternative explanations.

What type of procedures do you use in a lab to test for theory of mind?

In one study we just completed, our goal was to see if chimpanzees could recognize what others were actually seeing, and not just what they were looking at (i.e. not just what they had a “line of gaze” to). We used a mirror to investigate this. Chimpanzees are good at recognizing themselves in mirrors, but we wanted to know if they could also recognize that a human experimenter could see them in a mirror.

We had an experimenter sit in front of the chimpanzee enclosure. In one condition, he looked over his shoulder into a mirror for several minutes at the chimpanzee’s reflection. In another, he looked over his shoulder, but the mirror was turned to its non-reflective side, so he couldn’t see the chimpanzee. We found that the chimpanzees made significantly more visual attention-getting gestures when the mirror was facing forward than when it was facing away, and they made almost as many gestures as they did in a third condition where the experimenter was looking directly at them. So we have evidence that the chimpanzees knew the experimenter could see them in the mirror, even though he did not have a direct line of gaze to them.

Quite apart from the knowledge you’re gathering, what are some practical applications for this research?

Possessing theory of mind confers a huge adaptive advantage for survival and reproductive success, because it allows one to predict others’ behaviour from their hidden mental states (instead of just from their current, observable behaviour). If you have a more accurate way of predicting another’s behaviour, you can better plan your own behaviour to achieve the best outcome for yourself.

Recognizing that others have inner mental lives also allows us to do things to influence their mental states in ways that can benefit us. For example, we can deceive others into believing we are stronger, richer, or braver than we really are by behaving in certain ways. But just because we are able to think about others’ inner mental states doesn’t necessarily mean other species can.

Investigating theory of mind in chimpanzees can potentially be of great benefit. For example, if we can discover how individual differences in chimpanzees’ theory of mind skills are related to differences in their genes and brain structure, this could be important in understanding human disorders such as autism.

It will also help us design better environments to care for chimpanzees. Thousands live in zoos, research facilities and sanctuaries. They cannot be released into the wild because they were born and grew up in captive environments, it’s all they’ve ever known, and they would not survive in the wild. What we can do, however, is make their lives as comfortable as possible.