Theory of Mind in Animals

Supposing that some nonhuman animals can think, the question then arises: can they think about thought itself? Given that they have minds, do they recognize this fact? It is by no means guaranteed, for it is possible to possess a property unknowingly. Perhaps animals are limited to thinking about the physical world, so that, whilst capable of simple reasoning about their own behaviour and others’, they lack any conception or awareness of the mental states that underlie this behaviour. The question thus becomes whether animals possess any mentalistic concepts, such as belief or desire, which they attribute to themselves or others, as part of a general ‘theory of mind’. We must be wary not to take a positive answer for granted. Mentalistic attributions come so naturally to human observers that we may be predisposed to assume that other animals share this ability. As Byrne puts it: “we, as normal humans, find it hard to imagine not being able to understand another’s mental viewpoint.”[1] We are masters of the intentional stance,[2] automatically interpreting behaviour as goal-directed, and using this to make inferences about the agent’s beliefs and desires. But despite how easy this seems to us, it is actually quite a cognitive feat, and we cannot assume that evolution will have seen fit to equip other animals with this same ability. Instead, we must look to the empirical evidence for answers.

According to Gallup’s famous “mark test”, you can assess whether an animal is self-aware by whether it can learn to recognize itself in a mirror. In particular, if you secretly mark the animal’s forehead, and it sees this mark in the mirror and responds by touching its own forehead, then this suggests that the animal recognizes itself in the mirror. But this does nothing to show that the animal has knowledge of its own mind. After all, all creatures have some means of distinguishing their own body from those of other animals, and we would not be surprised if an animal touched a mark directly visible on its paw.[3] But a mirror is simply a perceptual tool of a certain kind, allowing creatures to see things that they otherwise might not. In light of this, why should the implications of mirror self-recognition be so different in kind? Granted, it does demonstrate a form of intelligence, or perceptual resourcefulness, for an animal to learn to make use of a mirror for self-exploration. But the mirror test is largely a red-herring so far as research into animal theory of mind is concerned. Passing the mirror test is not sufficient for self-awareness, as explained above. Creatures need not have mastery of mentalistic concepts to recognize themselves. They might identify their body without thereby realizing that the body contains a mind. And neither does the test identify a necessary precondition for self-awareness. In testing visual perceptual flexibility, it disadvantages creatures which favour other sensory modalities such as hearing or olfaction. And an animal might, plausibly, be capable of thinking about its own mental states whilst lacking the perceptual skills required to recognize its body via indirect means. What we really need to test is conceptual, not perceptual, skills.

One promising line of research investigates animals’ self-monitoring of their own mental states. For example, dolphins were trained to distinguish high from low pitched tones, and were rewarded for selecting the correct paddle. As one would expect, they often made mistakes when the tone was close to their discrimination threshold. Interestingly, when an ‘escape’ paddle was introduced – a safe fallback option with no reward or penalty – the dolphins would often select this option in response to tones near their discrimination threshold.[4] A fairly intuitive interpretation would see the dolphin’s “escape” response as signalling its uncertainty as to which of the two other options – “high” or “low” tone – is correct. This interpretation suggests that dolphins can reflect on their own mental states, assessing their subjective confidence in their own judgments, just as humans can. That is, it suggests that dolphins know their own minds.

This conclusion is not assured, however, for deflationary alternative interpretations of the escape response are possible. The metacognitive explanation is second order, i.e. the dolphin’s response expresses a judgment about its own mental states. But it could just as well be a first-order judgment that is solely directed at the external stimulus. Perhaps the dolphin judges that the tone is both high and low, and this ‘cognitive conflict’ – absent any personal recognition of the conflict – causes it to select the escape option.[5] Thus, while these experiments do at least suggest that dolphins have some functionally metacognitive capabilities, being sensitive to the reliability of their own mental states, this does not establish that they possess mentalistic concepts.[6]

But perhaps we are looking in the wrong place. Perhaps second-order thought is more open to experimental verification when directed at the thoughts of others, rather than oneself. Whilst first-personal metacognitive processes might be helpful for regulative purposes, they are not easily distinguished from sub-personal functional equivalents, and the extra information provided by meta-level knowledge of one’s own fallibility seems only moderately useful from an evolutionary perspective. By contrast, the benefit of attributing mental states to other animals is clearly immense, due to the predictive power it provides. Such capabilities are also more open to empirical investigation, as some third-personal mentalistic attributions are comparatively difficult to ‘deflate’.

Tactical deception is an appealing candidate behaviour for second-order intentional interpretation. These involve cases whereby an animal achieves their goal by causing another animal to obtain a false belief. Byrne describes an example wherein a young baboon named Paul found an adult, Mel, who had just dug up a corm, and subsequently fooled his mother into chasing his rival away:

“[Paul] looked around, seeing no other baboon, and screamed loudly. His mother, who was higher ranking than Mel, ran into view grunting aggressively and immediately pursued Mel. When they had both left the immediate area, Paul ate the corm.”[7]

Despite their appeal, such anecdotes provide unreliable evidence for intentional deception. Paul’s behaviour can be explained by his previously learning the correlation between screaming in certain circumstances and thereby obtaining the food reward. Or, more generously, we might even grant that he recognized that screaming would cause his mother to appear and chase off Mel. But neither of these interpretations require that Paul understands his mother has a mind, so we cannot be sure that his intention was to evoke her false belief.

More generally, we are faced with the problem of how to empirically distinguish first-order from second-order intentionality. Given that any case of tactical deception in animals will be instrumental to obtaining some behavioural output from the target of deception, we might plausibly hold that the deceiver merely intends to provoke this behaviour, rather than the false belief that underlies the behaviour.[8] The question then arises how the animal obtained the means-ends belief that his deceptive act would cause the desired behaviour. There seem two plausible candidates: either the animal has learnt from past experience, or else it has some rudimentary understanding of the causal processes underlying behaviour – i.e. a theory of mind – from which it can make successful predictions. Byrne claims that tactical deception has been observed in great ape populations that are under continuous observation, which allows us to rule out previous trial-and-error learning, and thus provides strong evidence for mentalism in these species.[9] Granted, it is possible for goal-achieving novel behaviours to arise through lucky coincidence, but as Dennett points out, once a broad enough range of examples start to pile up, “the claim that it is all just lucky coincidence… becomes the more extravagant hypothesis.”[10]

So far we’ve focused on general evidence, but it is also worth considering the specific abilities that a theory of mind might involve. The most fundamental component is perhaps an understanding of goal-directed behaviour, whereby one recognizes that other creatures are agents whose actions aim at achieving particular goals. Premack’s experiments suggest that chimpanzees are capable of inferring the goal of an actor’s behaviour – correctly selecting the photograph of a ‘solution’ to a videotaped actor’s ‘problems’ – when three year old humans cannot; though these results are controversial.[11] A more advanced step is to recognize that others can have different beliefs from oneself. Humans typically develop this ability at around the age of four, but it isn’t clear whether any other animals can do the same. For example, Cheney and Seyfarth have found that monkey alarm calls are insensitive to the knowledge or ignorance of their audience.[12] However, some chimps can learn to discriminate between trainers that were or were not present to perceive a critical event – a capacity related to recognition of others’ ignorance.[13] We may further ask whether animals are capable of tracking what others perceive. Apes can use the target’s bodily orientation to judge whether to send a visual signal, and some show evidence of understanding the specific importance of eyes in visual perception.[14] While some such results might merely show that apes can use direction of gaze as behavioural cue, language-trained chimpanzees responded correctly to the question “what’s that?” when asked for the first time without pointing, with the trainer instead merely looking at the target. Whiten suggests that this “reinforces the conclusion that chimpanzees do in fact see visual attention as ‘about’ something.”[15] This would seem to constitute a rudimentary form of second-order intentionality.

In sum, it isn’t entirely clear whether any non-human animals have an understanding of minds. There’s certainly scant evidence that they have the rich conceptual understanding that humans do. But some of the more advanced animals might at least exhibit important precursors to a theory of mind. Dolphin behaviour is sensitive to their own uncertainty, even if we cannot be sure that they are aware of this themselves. There is some evidence that apes have some of the core capabilities that amount to a theory of mind, including an understanding of others’ goal-directed behaviour, visual perception, and possibly ignorance. Anecdotes relating tactical deception are especially enticing, though open to deflationary interpretation if not found under controlled conditions. Further research is required to reinforce and build upon these initial successes – or expose their limitations.

Bibliography

Bennett, J. (1991) ‘How to Read Minds in Behaviour’ in A. Whiten (ed.), Natural Theories of Mind. Oxford: B. Blackwell.

Browne, D. (2004) ‘Do Dolphins Know Their Own Minds?’ Biology and Philosophy 19: 633-653.

Byrne, R. (1995) The Thinking Ape. Oxford: Oxford University Press.

Cheney, D. and Seyfarth, R. (1990) How Monkeys See the World. Chicago: University of Chicago Press.

Dennett, D. (1987) The Intentional Stance. Cambridge, Mass.: MIT Press.

Premack, D. (1988) ‘‘Does the chimpanzee have a theory of mind?’ revisited’ in R. Byrne and A. Whiten (eds.) Machiavellian Intelligence. Oxford: Oxford University Press.

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

Whiten, A. (1997) ‘The Machiavellian Mindreader’ in A. Whiten and R. Byrne (eds.) Machiavellian Intelligence II. Cambridge: Cambridge University Press.

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[1] Byrne (1995), p.109.

[2] See Dennett (1987).

[3] Derek Browne, lectures; Tomasello & Call (1997), p.337.

[4] Browne (2004), p.641.

[5] Ibid, p.647.

[6] Ibid, p.651.

[7] Byrne (1995), p.124.

[8] Bennett (1991), p.104.

[9] Byrne (1995), p.133.

[10] Dennett (1987), p.251.

[11] Premack (1988), p.176. But cf. Tomasello & Call (1997), pp.319-322.

[12] Cheney and Seyfarth (1990), pp.219-222.

[13] Whiten (1997), p.161, describes experiments by Povenelli to this effect.

[14] Tomasello & Call (1997), p.340.

[15] Whiten (1997), p.165.