Critically assess the claims that animals, particularly chimpanzees, have a human-like understanding

Psychologists have long established that most humans are accomplished mind-readers. As social animals, the ability to understand what other people are thinking is vital to our social efficacy. In normal human development a child begins to follow its mother's gaze at an early age and eventually realises that the mother has thoughts and feelings of her own.

Researchers have shown the child is soon able to effectively read the care-giver's mind. This ability becomes more and more sophisticated as we get older, as we have to deal with the complexities of social life. But how do our mind-reading abilities compare to other animals, especially those that are most closely related to us genetically, chimpanzees? What do they understand about conspecifics (other members of their own species) and is there any way for us to really know what it is that they understand?

While much research has been carried out into what animals understand about each other, there is a huge amount of debate over what the findings really mean. Even over the last decade there has been some remarkable turnarounds by the major researchers in their opinions on this matter. In their influential book 'Primate Cognition' Tomasello & Call (1997) present the case that primates do not really understand the psychological states of conspecifics. What they do understand is the behaviour of conspecifics. For example they learn to associate load noises with all those around them running away. In their review of more recent findings, however, Tomasello Call, & Hare (2003) state that the situation has now changed and there is evidence that chimpanzees - as most of the research has been done in chimpanzees - do, in fact, understand something about the psychological states of conspecifics. The real question is, which psychological states do they understand and how much about them do they understand? What, then, has happened in the research over this intervening period to bring some researchers to these new conceptions?

Early studies cited anecdotal evidence to show that chimpanzees had a theory of mind. For example Whiten & Byrne (1988) explained how chimpanzees often appear to deceive each other in the wild for tactical reasons. Critics of this sort of anecdotal evidence complained that it was easy to construct a method for how these types of behaviours might have developed without the requirement that the chimpanzee might be able to reason about the psychological states of conspecifics. An alternative approach was required.

In order to be interested in another person's state of mind, it is necessary to be looking at them and taking notice of their behaviour, even before making any guesses about what that behaviour might mean. Povinelli & Eddy (1996) examined how chimpanzees reacted to the type of eye contact that was directed towards them. They report two experiments, the first of which found that chimpanzees were more likely to gesture for food from a person who had made eye-contact with them. In the second they looked at the effect of head orientation and head movement. The researchers also found that this was important in which researcher the chimpanzee chose to gesture at. These kind of results might be construed as evidence that chimpanzees do have a theory of mind, after all young children are aware of gaze direction and make inferences from it. But Povinelli & Eddy (1996) admit that their results are open to two different interpretations. The first is that there is an attentional bias, that the chimpanzee has a behavioural connection triggered between the gaze and the possibility of getting food. The second interpretation might be that there is evidence of a theory of mind, although it might only be evidence that the chimpanzee understands attention is important, not that it understands what the person is thinking.

While the evidence from this study is open to interpretation, that carried out by Hare, Call, Agnetta & Tomasello (2000) is more specific. Theoretically they concentrate on a line of evidence that comes out of Povinelli & Eddy's (1996) findings and focuses on the visual perception of chimpanzees. Hare, Call, Agnetta & Tomasello (2000) in reporting the evidence about how chimpanzees follow gaze, state that the evidence indicates that it is only in some situations that they are able to use this information effectively. They criticise previous research for involving chimpanzees in an unnatural test. Instead they devised an experiment that placed a subordinate and dominant chimpanzee in competition for two pieces of food. They varied the conditions in which the two pieces of food were visible to each of the chimpanzees. When the subordinate chimpanzee could see food and the dominant chimpanzee could not, and when the subordinate chimpanzee had a head start they tended to go for the food only they could see. This ruled out the possibility that one chimpanzee was monitoring the other for cues. What this research suggests is that chimpanzees seem to be able understand what a conspecifics can or cannot see. Otherwise it is difficult to explain the behaviour of the chimpanzees in this experiment. Another variation of this experiment in which the dominant chimpanzee could see the hidden food tended to confirm the experimental hypothesis, as in this situation the chimpanzee went for the visible food first. Furthermore they suggest that a test, like this one, that involves no training and little setting up is more natural and so more likely to find an effect.

These results seem very convincing, but the research has not been so clear cut. Karin-D'Arcy & Povinelli (2002) carried out a series of experiments were they failed to replicate the full results of Hare, Call, Agnetta & Tomasello (2000). The problem was that it appeared in this research that the chimpanzees were not able to distinguish between when their rival was able to see the food and when they were not. The authors of this study differentiate between two hypotheses, the visual perspective theory (VPT) and the peripheralised feeding hypothesis (PF). The former requires that the chimpanzee does not approach the food that is visible to the other chimpanzee first. The latter states that in a competitive situation chimpanzees tend to avoid food in the open and be more attracted to food near physical structures. Karin-D'Arcy & Povinelli (2002) argue that in not fully replicating Hare, Call, Agnetta & Tomasello's (2000) study, the findings do not support the VPT, but could be more parsimoniously explained by the PF hypothesis. Povinelli & Giambrone (2001) make the same point saying that chimpanzees in the wild quickly learn that they will be beaten if they take food that is out in the open. Essentially while the behaviour may indicate an understanding of mental states, an alternative behavioural hypothesis may be more parsimonious.

Tomasello, Call, & Hare (2003), however argue that these alternative hypotheses are not valid as their second set of experiments only involved the use of one set of food. In addition they ran a control experiment in which they tested whether the chimpanzees preferred food next to barriers: they did not. In trying to explain the mixed results from these experiments they argue that chimpanzees in the wild do not generally communicate about the location of food to each other in the wild. Their experiments, they claim, are better because they place more emphasis on naturalistic conditions. It could still be successfully argued, however, despite these claims, that they have not fully rebutted the criticisms of Karin-D'Arcy & Povinelli (2002). Tomasello, Call, & Hare (2003) do report a separate line of evidence from an unpublished study (Call et al. unpublished) in which they claim to have found that chimpanzees can understand the intentional states of others. In this research chimpanzees seemed to understand the difference between a human who was trying to complete a particular action and one simply teasing them.

While this line of evidence about chimpanzees in various situations provide some interesting evidence, it is relatively easy to criticise on the fundamental basis that they are still not showing an understanding of mental states. Povinelli & Vonk (2003) make the point that it is only natural for us, as humans, to assume that chimpanzees, our closest relatives, have similar thought processes to us - they look in our eyes and appear to frown, might they not be thinking the same thing as us? The argument is turned around: is it possible that we are reading too much into the simple learned and genetically inherited behaviour of animals? Povinelli & Vonk (2003) argue that although we share considerable genetic similarities with chimpanzees, we are still not that similar in evolutionary terms, even compared to our closest relatives humans are still completely different in many ways. They again raise the 'reinterpretation hypothesis', also outlined in Povinelli & Giambrone (2001). This hypothesis makes a distinction between first order and second order intentional. The first contains all of those mental states that both humans and chimpanzees share, the second contains all of those that are commonly described as indicating a theory of mind - or a real understanding of other's mental states. The theory posits that the same behaviours can be launched by either first order or second order mental states, but only when an understanding of the theory of mind is present are second order states seen to regulate and organise those behaviours. Suddendorf & Whitten (2001) make the case for the presence of second order states in the great apes but Povinelli & Vonk (2003) explain that the debate on understanding of mental states tends to end up with deciding which explanation of behaviour is more parsimonious. Since inevitably, this is an extremely difficult task, an alternative experimental paradigm is required. They suggest that one example of this type of paradigm is the situation in which one being has to make an extrapolation of its own thoughts onto the mental states of another. In other words making assumptions about another being's behaviour from its own experience. Perhaps this will provide a way forward at this interpretational impasse.

Chimpanzees, while being closely related to us are not the only animals in which an understanding of mental states has been examined. Hare, Addessi, Call, Tomasello & Visalberghi (2003) applied similar experimental paradigm as Hare, Call, Agnetta & Tomasello (2000) to investigate what capuchin monkeys understand about the mental states of others. In this research the subordinate monkeys were released before the dominant monkeys but did not show a preference for the food that was hidden from the view of the dominant monkey. Therefore they found little evidence that capuchin monkeys understand the mental states of conspecifics. Interpreting this data, it can easily be postulated that capuchin monkeys simply do not have the same level of understanding as chimpanzees - however those findings are interpreted.

More concrete evidence about the understanding of mental states in animals comes from the study of domestic dogs. Miklosi, Polgardi, Topal, & Csanyi (1998) found that dogs were able take cues from the experimenter to find hidden food including the bowing of the head, pointing, head turning and pointing. The dogs were also able to take their experience from their owner and generalise it onto a stranger. While this is intelligent behaviour it does not at first show evidence of understanding of mental states, more of the following of behavioural cues. Soproni, Miklosi, Topal, & Csanyi, (2001) carried out an extension of this type of study, in fact a parallel of that carried out by Povinelli & Eddy (1996) (discussed earlier). This research looked at how dogs interpret four different types of directional cues: glancing only, head-nodding, pointing and gazing and head turning. The results showed that dogs behaved more like children than chimpanzees in response to these experimental conditions. They showed a greater propensity to interpret the behaviour as a form of communication than did the chimpanzees. These results are open to a similar range of interpretations as previous findings, including the idea that dogs have had extensive experience in interpreting human gestures so the behaviour might be learned. Still Soproni, Miklosi, Topal, & Csanyi, (2001) argue that because of the adaptability of the dogs, their data supports the hypothesis supports a higher level of understanding of mental states.

What is clear from the vociferous debates in the literature is that whether chimpanzees and other animals understand much about each other's mental states is a highly controversial topic open to various interpretations. Summarising, Tomasello, Call, & Hare (2003) claim that chimpanzees monitor the gaze of others, appear to know what conspecifics are seeing as well as understanding something about the intentional states of others and Soproni, Miklosi, Topal, & Csanyi, (2001) show that dogs may have similarities in understand of gesture with children. Perhaps the most damning argument of these approaches comes from Povinelli & Vonk (2003) who suggest that using the current methodologies an answer is practically impossible and an alternative paradigm is required to push the debate forward.

References

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

Hare, B., Addessi, E., Call, J., Tomasello, M., Visalberghi, E. (2003) Do capuchin monkeys, Cebus apella, know what conspecifics do and do not see? Animal Behaviour, 65, 131–142

Karin-D'Arcy, M. R., Povinelli, D. J. (2002) Do Chimpanzees Know What Each Other See? A Closer Look. International Journal of Comparative Psychology, 15, 21-54.

Miklosi, A., Polgardi, R., Topal, J., & Csanyi, V. (1998). Use of experimenter-given cues in dogs. Animal Cognition, 1, 113-121.

Povinelli, D. J., Eddy, T. J. (1996) Factors Influencing Young Chimpanzees' (Pan troglodytes) Recognition of Attention. Journal of Comparative Psychology, 110, 4, 178-191

Povinelli, D. J., & Giambrone, S. (2001). Reasoning about beliefs: A human specialization? Child Development, 72, 691-695.

Povinelli, D.J. & Vonk, J. (2003). Chimpanzees minds: Suspiciously human? Trends in Cognitive Sciences, 7, 157-160.

Soproni, K., Miklosi, A., Topal, J., & Csanyi, V. (2001). Comprehension of human communicative signs in pet dogs (canis familiaris). Journal of Comparative Psychology, 115, 122-126.

Suddendorf, T., & Whitten, A. (2001). Mental evolution and development: Evidence for secondary representations in children, great apes, and other animals. Psychological Bulletin, 127, 629 – 650.

Tomasello, M., & Call, J. (1997). Primate cognition. New York: Oxford University Press.

Tomasello, M., Call, J., & Hare, B. (2003). Chimpanzees understand psychological states – the question is which ones and to what extent. Trends in Cognitive Sciences, 7, 153-156.