"Knowing you, knowing me":
Can other animals have an identity crisis?
Professor Keith Kendrick
In my last lecture I made the point that if one was unable to demonstrate that an animal species could recognise others as individuals, then its members could hardly be expected to be capable of awareness of self. Indeed, this is why the title of my lecture has deliberately misquoted the words of the ABBA song to read "Knowing you knowing me" rather than the correct version of "Knowing me, knowing you". This is not simply playing with words but tries to make a serious evolutionary point. While as humans we appreciate that self-awareness is an essential tool for appreciating and predicting the thoughts and actions of others it was not essential to evolve this ability first in order to consider and react to others as individuals. The first step was undoubtedly for the perceiver to identify others as individuals and be able to directly interpret the possible immediate consequences of their actions. This can be done through simple learned associations and does not necessarily imply that a perceiver is, in any real sense, actually consciously aware of him or herself.
To simply be able to recognise and respond to the actions of other individuals has two serious limitations. In the first place you are locked in the present and what you can sense directly, in the second place you have no way of really appreciating the psychological processes and intentions behind the actions of others. At this stage many would consider that the next phase was to develop self-awareness so that by appreciating one's own experiences one can respond to others better by being able to attribute the same experiences to them. This is something of a non-sequitor however because the evolutionary driver is being better able to interpret the actions of other individuals. In theory therefore one should have developed the capacity for appreciating the importance of perceiving psychological processes in others first before developing self-awareness to improve this skill. The same point has been made by the philosopher, Strawson (Strawson 1958/64).
What this means when we are considering other species is that we might expect to find evidence for some where individuals are able to detect psychological processes in others without the ability to be aware of similar processes in themselves. This sounds strange, and even contradictory, but what we are mainly talking about is having the ability to detect intentions to act in a particular way (i.e. to be able to predict how another individual is going to act in advance). To achieve this one would need to be able to detect very subtle nuances in the behaviour of another individual and to link these to the likely course of action they may subsequently perform (i.e. groom you, attempt to mate with you, attack you etc.).
From an evolutionary standpoint one could postulate that the ability to detect intentions in other individuals may have called for greater and greater sophistication in sensing minute behavioural changes in others. This may of course be extremely difficult to achieve and not give that much advantage in terms of advance warning of the likely actions of another individual. The next step would therefore have been to appreciate how external events lead to the formation of an intention to act. While it is still possible to take this step without an individual having self-awareness, it is clear that using your own experience as a yardstick can be more effective for devising general rules. We would therefore expect that animal species with the capacity for self-awareness would be likely to show ability to understand how external events can lead another animal to form an intention to act in a particular way (even if it is actually the wrong course of action). This would result, for example, in the ability to deceive or empathise.
The problem of consciousness
All this of course makes a massive starting point assumption that some form of consciousness is widespread in other species. The capacity for self-awareness obviously requires consciousness but even some of the steps leading up to its evolution must require some capacity for it as well. However, in many respects it is less difficult to accept, although difficult to prove, that other species are capable of consciousness than it is to accept the more contentious issue that other species can be conscious of a sense of self and to appreciate that others do the same.
The main arguments against consciousness in other species are that:
1. Computers can achieve most of what animals can do without consciousness. This at first sight always seems a convincing argument although if you think about it, as humans, we are unable to perform even simple arithmetic tasks without consciousness. Indeed, likening computers to brains may be useful for descriptive processes but misses the all important point that brains do not work in the same way as computers. For brains, most complex problem solving activities demand consciousness.
2. Neuropsychological studies on humans, and indeed our own experience, have shown us that much can be achieved without awareness. For example, the phenomemon of "blindsight" in humans that has been studied extensively by Larry Weiskrantz has revealed that human patients with damage to the visual areas of their brain may report complete loss of visual awareness (i.e. they say they cannot see anything) but can nevertheless be shown in formal tests to be able to discriminate visually between objects. We also know that we can negotiate quite complex environments when sleepwalking or find ourselves driving or walking to familiar places without being aware of doing so. Similarly we all realise that we must experience complex dreams every night but only become aware of them when we are woken during particular phases of sleep.
All that these latter observations show us however is that the brain can do a number of things without you being aware of them. Of course this is actually true for a whole host of other bodily functions that the brain regulates. What is equally true for us is that there are many things we cannot do without consciousness, and it would be difficult to postulate that other species, which are also capable of highly complex behaviours, do not have at least some capacity in this respect. What we can say is that for many other species, the amount of time spent in conscious mode may be quite limited since their life-styles do not require it. Indeed, a conscious brain is generally a very active one and therefore acting in conscious mode is a very energy consuming business that should be avoided wherever possible.
Self-awareness and the problem of identity
What are the implications of having self-awareness?
As humans we know only too well the often painful process of introspection and self-doubt that can lead to depression or even an identity crisis if we feel that our own mental processes are different from those around us and are apparently belittled or even despised by them. Such feelings are the result of the heightened sense of self-awareness that humans have developed. Are we alone in having to fight such self-generated demons? Do other species have similar powers of self-awareness with their dual potential for promoting both feelings of worth and improved appreciation of the likely actions, needs and feelings of others on the one hand and feelings of negative worth, depression and even self-destruction on the other?
This is a highly controversial question since arguably it is our human capacity for self-awareness which drives our thought processes, artistic and creative abilities and, of course, our conception of the existence of life beyond death and of higher beings that may control our destiny. In a real sense it is our combined abilities to think and to be the object of our own attention that have allowed us to ascribe moral values to our own actions and to those of others. For me, one of the most telling observations to come from Shakespeare's pen is when he makes Hamlet observe "there is nothing either good or bad but thinking makes it so". Without thought and self-awareness the concepts of good and bad are indeed meaningless.
As humans we find it hard to conceive that other species are not aware of themselves as we are and I remember being fascinated as a child by Hans Christian Anderson's story of "the ugly duckling". Could the fostered swan really know that it was not a duck? Years later as an undergraduate I became a devotee of the Norwegian playwright Henrik Ibsen and in his play Brand he puts forward this same idea that other animals might be aware of being misfits:
"When I was a boy, I remember,
Two thoughts kept occurring to me, and made me laugh.
An owl frightened by darkness, and a fish
Afraid of water. Why did I think of them?
Because I felt, dimly, the difference
Between what is and what should be; between
Having to endure and finding one's burden
(Brand, Act 1 – translated by Michael Meyer)
The idea that animals could experience all the negative emotions of a human misfit or a Hamlet, Caliban or King Lear is a serious issue given that, as humans, we impose unnatural social and physical environments on companion, domestic and wild animal species. Up until the early 1970s no scientist had seriously considered the question that other animals may have minds and self-awareness, let alone come up with formal ways to test if they do. Since that time it has remained one of the most controversial and hotly debated areas of psychology and behavioural science. Of course such a fundamental issue is not the exclusive domain of psychologists and the subject has received enthusiastic attention from sociologists, philosophers, theologians, moralists, writers and even computer scientists.
The reason for the hot debate is that much is at stake depending upon the outcome of the final answers that are provided. If other animals are not aware of themselves not only does this make humans unique it also challenges Darwin's evolutionary theories. As we have seen already in my lectures every other aspect of human behaviour is exhibited, at least to some degree, by many other species, as one would predict if we have common ancestry. If self-awareness is only present in humans it would represent a trait that has evolved in a single species. From another standpoint of course, if other species have minds and self-awareness it would greatly enhance their capacity for suffering and increase the importance for considering their moral right to freedom from human control.
So what approaches have been taken so far to address this difficult issue? In the first place numerous individuals have sought to break down self-awareness into different levels or component parts. There is fairly general agreement that there are three broad levels on which self-awareness can operate:
1. First order representation is where awareness of self is exclusive and achieved without the ability to attribute the same state to others – i.e. imagine you and another individual are eyeing up another attractive person. You might be thinking "they're attractive I must make a move to get noticed" but you would not know that the other individual eyeing the same person might have the same thoughts.
2. Second order representation extends to being able to attribute mental states to others (i.e. a representation of a representation). In this case in the same situation you would be aware that the other individual is having the same thoughts as you and you might therefore be thinking "they're attractive, but I've got competition, better make my move fast!"
3. Third order or "metarepresentation" means being able to conceive of second order representations in others (i.e. a representation of a representation of a representation). In this case the example might be that you see that the person you are attracted to is also attracted to you and realise that the other person eyeing up the same individual has understood this and is annoyed that they have missed out.
We know that as humans we are capable of all of these levels of representation but what about other animals?
The story of the monkey in the mirror
In 1970 Gordon Gallup Jr published a landmark paper in Science (Gallup, 1970) which has been the subject of controversial debate ever since. He reasoned that if animals could recognise their image in a mirror as a representation of themselves rather than of another individual then they must have self-awareness in the sense that they could become "the object of their own attention".
He started, not surprisingly, with one of our nearest relatives, the chimpanzee. Since these animals had not experienced mirrors before he first gave them experience of seeing their image in a mirror for 10 days. The animals were then anaesthetised and small dye marks put over one eye and on the tip of the opposite ear. They were then allowed to fully recover and given the mirror again to see whether they showed any interest in the marks on their head that could not be seen except by using the mirror.
Results showed that when the animals first encountered the mirror they interpreted the image as representing another individual and so for the first few days they showed high frequencies of social behaviours towards the mirror. These then declined and clear evidence could be seen of the animals inspecting themselves using the mirror i.e. making faces into it and using it to look at parts of their body that they could not normally see.
When the animals woke up from anaesthesia they immediately started investigating and touching the marks on their faces although for the most part they fairly rapidly seemed to get bored with doing this.
Since this original study 73 out of 163 chimpanzees have been shown to pass this specific mirror test, 5 out of 6 orang-utans but only 6 out of 23 gorillas.
The apparent problems that gorillas have with this task have been the subject of much debate. These animals do seem to use mirrors to examine themselves but since they do not touch the marks on their faces it has been argued that perhaps they are just less motivated to do so. Karyl Swartz and Robert Shumaker (see the Cognitive Animal 2002) came up with a modification of this task where animals were actually rewarded for removing stick-on spots from their body and found that they learned rapidly to do this for spots placed on their heads - which could only be seen by using a mirror. However, since the spots were placed on the animals without anaesthesia they learned quickly to simply wipe their brows even without the mirror. The experimenters then changed tack and used a laser pointer to shine a spot on the animal's head (i.e. the animal could not know when this was happening). The animal could use the mirror to touch the spots under the chin to get a reward but not, interestingly, when they were on the forehead!.
Of the lesser apes, three gibbons have also been tested with the classical mirror self-recognition task and while a few showed clear evidence of self-directed behaviour in the mirror none passed the mark test.
What about monkeys other than apes?
There have been numerous attempts to show mirror self-recognition using the mark test in both Old (baboons, guenons and a number of species of macaques) and New World (owl monkeys, marmosets and tamarins) monkeys and prosimians (lemurs and bush-babies). While occasional claims for success have been made, these have usually been impossible to replicate or have had some fundamental methodological flaw. Perhaps the best example to give is once again work by Gallup himself where even monkeys given years of experience with mirrors failed to show either self-directed behaviour or pass the mark test. They did however learn to use the mirror to detect individuals approaching them from behind!
Dolphins in the mirror
Apart from the great apes Dolphins also have the greatest reputation for intelligence so can they show evidence of mirror recognition? In a recent study Reiss and Marino (2001) claimed to have shown good evidence for this in two animals. The animals showed clear use of reflective surfaces in their pools at the New York Aquarium in Brooklyn to investigate marks that had been placed on their head and other body regions. An interesting difference between dolphins and apes is that the dolphins pay no attention to marks placed on the body or head of other individuals which might be taken as further evidence for specific awareness of self.
Other animal species in the mirror
Apart from a so far unpublished observation by Patricia Simonet on a 45-year old elephant mother and her 8-year old calf (performers in a Los Angeles casino) which apparently passed the mark test, no other mammalian or avian species looked at has shown any clear evidence for mirror self-recognition. Like most Old and New world monkeys it is clear that when an animal views itself in the mirror it reacts as if it is seeing another individual and may well show extreme aggression towards it.
Humans in the mirror
Human infants do not normally pass the equivalent of Gallup's mirror recognition test until 18-24 months of age (obviously anaesthetics are not used in this case and the mark is normally placed on the nose). Indeed it is extremely rare for any individual to be able to recall events or experiences before this self-recognition stage is reached (so called "infant amnesia"). However, in an interesting variation of the task where video tapes are recorded of the marking procedure and then a few minutes later played back through a television, individuals need to be closer to four years old before they make the link that the child in the video is actually them and act to remove the mark on their face. No other species has ever passed this video test variation!
So does passing the mirror self-recognition test constitute proof of theory of mind?
If we accept that evidence for recognising oneself in a mirror as proof of awareness of your own psychological processes, the theory should be that the species that pass this test will show good evidence for being able to attribute mental states to others (i.e. at least the second order representation described earlier). Do they, or is mirror recognition only evidence for first order representation (i.e. awareness of you own thought but not of those of others)?
This is where most of the controversy really starts. It is obviously really difficult to devise good strategies for getting animals to show that they are aware of mental processes in others. There have however been some interesting attempts and one must remember that in most instances the requirement for the animals to demonstrate that they have a theory of mind is that they perform the tasks on encountering them for the first time. With practice animals will usually learn how to do even quite complex tasks but these can be done by simple rule learning rather than by appreciation of what others know or may be feeling.
Gallup for example reports a task where chimps have to join forces with humans to get a food reward. Here one individual is able to see which of a number of cups contains a food reward but cannot get access to them without the other individual using a handle to pull the cups within reach. The individual who had seen which cup contained the food had to then point to it so that the other individual could obtain it. Chimps were able to do this but could also happily switch roles with the human. Pairs of rhesus monkeys on the other hand could learn the task but seemed unable to switch roles with each other without having to completely re-learn the task. Gallup argues that this is evidence for cognitive empathy in chimps.
Knowing that someone can see you
Daniel Povinelli (a long term collaborator with Gallup) on the other hand, has come to the conclusion that chimps that pass the mirror recognition test may not actually be capable of such cognitive empathy. He has carried out a series of experiments that have tried to address the simple question of whether chimps know that others can see.
Chimps, like most non-human primates, readily beg for food from either humans or other animals. Povinelli simply asked the question whether they would realise immediately that there was no point begging for food from a human handler if the human's eyes were covered? The chimps themselves frequently played a game where they covered their heads with buckets or blankets and clearly knew that this stopped them being able to see what was going on (i.e. when they bumped into things they raised to bucket to see where they were). The first experiments therefore used a bucket to obscure the head of one of two human handlers but amazingly the chimps failed to show any immediate evidence that they knew they were better off begging from the other human who was holding the same kind of bucket but did not have their head covered. The chimps did of course learn quite quickly not to beg from the individual wearing a bucket but had they learned about the consequences of the importance of their being able to see or just to avoid begging from an individual wearing a bucket on their head? It seemed that they had not learned about the importance of another individual being able to see because if the bucket was substituted for a blindfold they went back to making random choices again.
Povinelli did find that the chimps would make the right choice if faced with a pair of humans where one was sitting facing and looking at them whereas the other was sitting with their back to the chimp and facing away from them. However it again appeared that this had more to do with the chimps having learned to beg from a human body that is turned towards you rather then whether the human could see them. Thus when an individual facing away from the chimp turned their head to face towards them they still avoided begging from them.
Two-year old humans that can pass the mirror self-recognition tests have no problem showing understanding that another individual needs to be able to see them in a similar context.
Evidence for false belief
One of the most crucial and accepted tests for establishing the presence of a theory of mind is that of false belief. This requires that an individual can either juggle mentally with two opposing solutions to a problem simultaneously, or show understanding that the beliefs of others can be very different from what we know to be true or to our own beliefs. A classic test of this in human children is a scenario where a child sees another child place an object in a container and then leave the room. The child's mother then enters the room and takes the object and places it in another container. The observing child is then asked which container the child will look for the object in when they return. Children under 4 years old typically indicate the one where the object currently resides (i.e. where the mother put it) whereas older children correctly indicate the container the child originally chose (i.e. they understood that the child will have a false belief that the object is still there). This seems like a simple task but chimpanzees do not seem to be able to progress to the false belief stage.
A number of species have been shown to employ deception strategies in order to maintain exclusive access to a food supply or a mate. However this does not necessarily imply attribution of mental states to others. There are amusing examples of individual vervet monkeys imitating the calls of a predator (a leopard) for their own gain. One of the nicest stories from chimps is of an individual called Sarah who was taught by observation the critical steps to setting up a record player and then had to provide help to one of her trainers to overcome deliberate problems with the set up (not plugged in or a cut in the power cord for example). She learned to indicate the solution to the problem to her favourite trainer even though she had nothing immediate to gain by doing so (i.e. it was not her problem really). Interestingly though she learned to deliberately offer the wrong solution to a trainer she did not like! This implies that the animal had the ability to know what others wanted to do and could use this knowledge to aid or hinder them achieving it (see Cheney and Seyfarth, 1990).
Empathy with other individuals showing grief or depression
Chimpanzees like most great apes, and indeed some other species, can be seen to exhibit something akin to grief or depression following some form of bereavement or separation from a close companion. However, even in apes it is rare for any other individual to ostensibly show emotional empathy and either join in by exhibiting the same emotional state or offer any form of physical consolation. This contrasts with observations of behaviour towards wounded members of a social group where other individuals (especially close family) will often help tend to wounds and feed the individual or in other ways adapt their life styles to help them recover. This is not however evidence that they can appreciate the emotional state of the wounded animal but could simply be a generalised response to the sight or smell of a wound and the survival advantage of maintaining numbers in a social group.
Many different animal species show clear evidence of imitation and this may even result in sophisticated tool use. Learning by social demonstration is widespread in the animal kingdom. Chimps and indeed some other primate species also seem to understand the importance of pointing and gaze direction to indicate where to look for things. However, being able to imitate others or guide them into looking at what you are looking at does not provide strong evidence for attribution of mental states to others or even a high-level of self-awareness.
Knowing your place and the places of others in a social hierarchy
Dorothy Cheney and Robert Seyfarth (1990) have also considered whether knowledge of positions in a social hierarchy and relationships between individuals may constitute evidence for a theory of mind. In many social mammals, and most notably primates, individuals within a social group do indeed seem to have a very accurate sense of social awareness in that they know their place within dominance hierarchies and even who is related to who. The latter is nicely illustrated by monkeys and apes who having been defeated or irritated by a more dominant individual are likely to vent their frustration by attacking or irritating one of the less dominant relatives of that individual. Similarly we have the example I gave in my previous lectures of vervet monkeys appreciating third party relationships using vocal recognition (i.e. they show knowledge that a particular baby is calling to a mother other than themselves). A final anecdotal example in vervet monkeys is the individual mimicking leopard calls to deceive other monkeys. This individual was very low down in the dominance hieracrchy and was seen to use this strategy when another individual was trying to join the group. By doing this the monkey prevented the new individual from joining the group and one might consider the motivation for doing this was the appreciation that the new monkey might occupy a more elevated position in the hierarchy (i.e. he was trying to stop having any more animals dominating him on a daily basis!).
However, it is not too difficult to come up with learning explanations to account for these observations which do not require attribution of a theory of mind.
So what might apes see in the mirror?
So what are we to make of all this? If Povinelli is right, then in chimps, unlike humans, mirror self-recognition does not indicate ability to attribute mental states to others (i.e. they may only be capable of first but not second order representation). What he and some others argue is that mirror recognition in apes is more to do with an appreciation of body image and movement than it is to do with self-concept. One argument that has been put forward (see Robert Mitchell in "The Cognitive Animal" 2002) is that large apes such as chimps and orangutans that have maintained an arboreal habitat needed to develop a more sophisticated visual appreciation of their body image to help move around optimally in the trees (a task that is effectively much easier for the majority of smaller monkeys). Thus when they see their image in the mirror they quickly recognise that it matches with their own self-image and can use it accordingly (i.e. the equivalent of "That's the same as me" rather than "That's me"). The argument is extended to postulate that since Gorillas have largely abandoned trees and are primarily ground dwellers they did not need to develop this improved visualisation of personal body image and hence find it difficult to see the match between the image in the mirror and that of their own body.
Support for this argument comes from the observation that any form of delay imposed between the chimps moving and seeing their image move on a video monitor seems to destroy their ability to treat the image as a representation of themselves. As humans we also have an internal visual representation of body image and this is demonstrated clearly by conditions such as anorexia where a distorted perception of this image can occur.
Thus a number of scientists are currently highly sceptical of, or completely reject, the possibility that even the great apes have a theory of mind that allows them to know what others may be thinking. Indeed, Povinelli has likened them and other animals to "radical behaviourists" in that everything they do is determined by their amazing abilities to learn associations between observable behaviours and their likely outcomes. This leaves only humans as "cognitive psychologists" capable of knowing that they know what others know.
This seems pretty extreme but does conveniently explain the major differences between humans and other species. However, we should be careful not to abandon the possibility of self-awareness in other animals too quickly. The majority of formal tests of awareness of mental states in others that are conducted on animals are assessing whether they are aware of information that others possess. Looking at the developmental sequence in humans we find that mirror self-recognition does indeed occur precisely at the time when children show clear abilities to attribute feelings and emotions to others. However ability to attribute informational states of mind does not occur until later. Thus it is possible that other animals that pass the mirror test may also be able to attribute emotional states to others. Indeed, many would claim that this ability is widespread in animals (not just ones that can pass the mirror test). However, one has to be careful in saying that this is mental state attribution rather than animals simply using their heightened sensory abilities to detect emotional states in others and matching this with previously learned associations about the likely consequences.
Another factor, which Gallup emphasises, is that mirror self-recognition is much slower to develop in Chimpanzees (than in humans). Thus few, if any chimps pass the test before the age of 8 years (compared with 18-24 months in humans). After this time between the ages of 8-15 years 75% of animals passed the test. Interestingly ageing has a big impact on this as well with only 26% of animals from 16-39 years passing the test. Thus failure to find good evidence for mental state attribution in chimps may have been contributed to by the fact that the animals only attain their peak performance for a short period of their lives.
Are there situations where humans fail the mirror test, or tests of theory of mind, and what can they tell us?
Apart from cases of brain damage, which I will deal with shortly, the main examples where serious impairments in mirror self-recognition or theory of mind tests occur are autism, schizophrenia, bipolar disorder and Alzheimer's. The same can often also be said for severely mentally retarded individuals. Like chimps we also show reduced abilities in this area with advancing age although in our case, effects are normally only observable in extreme senility. In most of these cases impairments in self-recognition are strongly associated with similar inability to accurately attribute mental states to others. So on the face of it these observations in humans strongly support Gallup's original theory that ability to recognise yourself in the mirror is likely to be good evidence that you can accurately attribute mental states to others.
So are most animals equivalent, for example, to autistic humans? I have already mentioned that many animals are quite good at detecting emotional states in others and so in this sense they might not be seen as equivalent to autistic humans. As I have already indicated this may be simply because other animals have developed better sensory skills than us for doing this. Indeed, one could argue that development of self-awareness and mental state attribution skills in humans may have contributed to a downgrading of our sensory skills for detecting emotional or even psychological states (notably in the area of odour detection!).
Alternative strategies for achieving theory of mind
Recent work on autistic humans has suggested that they can acquire an alternative method for correctly attributing beliefs and mental states to others. This is based on "picture in the head" teaching. If such individuals can learn to visualise "thought-bubbles" indicating the likely thoughts of others with whom they are interacting they show improved abilities to gauge their thoughts and pass tests of false belief (Wellman et al., 2003).
As I mentioned briefly in my talk on individual recognition the ability to form and use visual mental images may be quite widespread in the animal kingdom with my own work indicating that even the lowly sheep may be capable of this (Kendrick et al., 2001). Obviously animals without language could not imagine thought bubbles with words but on detecting a change in emotional or psychological state in another individual they could possibly generate a mental pictorial sequence to represent how that individual might act, based upon previous experience. Similarly perceived changes by an animal of external events or its internal state might lead to the generation of self-directed mental images of past events.
Thus past or present experience of events involving self in relation to others could occur in a largely involuntary way in animals (i.e. not under their own volitional control). This would be rather like having the ability to experience short action replays of past events as mental images in the head (it is easiest to consider these as visual but they could equally well be smell, sound or touch based or a combination). This might then allow animals, like humans with autism, to show a better appreciation of the consequences of emotional, motivational or even informational states in others without either being ostensibly self-aware or being able to actually empathise with them.
At first site this "action replay" scenario tends to suggest that other animals are no more than complex machines with a subscription to "Sky Digital interactive". However, the ability to re-run events mentally could potentially carry with it ability to re-run the corresponding emotional reactions to those events (a feature not yet integral to Sky Digital!). Thus animals would be capable of re-experiencing past stress or trauma.
What parts of the human brain are involved in self-recognition and what is different about them in other species?
Neuropsychological studies on humans with brain damage and functional brain imaging techniques have now given us a pretty good idea of the critical brain regions for self-recognition and an associated human theory of mind. These studies have now repeatedly emphasised a key role for the frontal cortex (Suss et al., 2001) and more recently the amygdala (Stone et al., 2003). In both humans and other animals, damage to these brain regions is often also associated with anti-social behaviours such as impulsivity and/or aggression and poor interpersonal skills.
Recent psychological and brain imaging studies have implicated the prefrontal cortex of the right brain hemisphere as being of particular importance for self face-recognition. Thus we are better at distinguishing our own face from that of a famous person when using our left hand to respond than when using the right. This is because the left hand is controlled by the right brain hemisphere. Similarly, brain imaging studies, and neuropsychological observations on human patients where some of the main connections between the two brain hemispheres have had to be cut, have also emphasised the importance of the right brain hemisphere for self-recognition. This is not just restricted to recognising your own face but also, for example, your own name (see Keenan et al., 2000).
These studies on humans do leave us with something of a problem when considering animals. The brain structures implicated in self-recognition and theory of mind are present to varying degrees in a number of different species and yet we are arguing that only humans have developed them. Although the frontal cortex in particular has increased in size considerably in humans compared with other animals, and Gallup argues that this expansion may explain why Gorillas fail the mirror test (their frontal cortex is less well developed than the chimpanzee or orangutan), it is difficult to satisfactorily explain the large difference between us and other species on brain size alone. Instead the differences must mainly reside in patterns of connectivity and this can also explain why problems can occur with autism and other human conditions even though brain size is normal.
Perhaps our development of language to increase communication and information exchange between individuals has progressively allowed the strengthening of feedback interactions between key brain regions to occur and with it development of greater voluntary control over imagining and thinking about past events. Such voluntary control would allow flexibility to put together diverse events occurring in separate contexts in order to run through multiple scenarios and thereby better predict the outcome of future actions or events. It would also progressively reinforce the concept and feeling of self.
So can other species have an identity crisis?
The evidence to date would suggest that no other species has the degree of self-awareness, introspection and knowledge about what others might think to develop the perception that they are social misfits and perhaps develop an identity crisis. Their failure to pass false belief tests in particular illustrates a lack of ability to appreciate that other individuals can have a different perspective from their own. You might argue that being unable to appreciate the fact that another individual is capable of having different information or beliefs from your own is an annoying trait in opinionated humans, particularly those that are in a position to control our lives. However, apart from some unfortunate individuals with developmental, psychiatric or neurodegenerative disorders we also appreciate the fact that the individuals concerned do have at least the potential for appreciating the views held by others.
Perhaps some of the best examples to support this view are the large numbers of animals raised by other species (usually humans) with minimal contact with their own. Such animals do not normally have major psychological problems and are rarely confused about which species they actually belong to.
Furthermore, when we have deliberately foster-reared sheep with goats and vice versa these animals have grown up preferring to socialise and mate with the species of their foster mother rather than their genetic one. We have never seen anything to support the view that such animals recognised the mismatch between what they looked like and what the animals they were attracted to looked like (Kendrick et al., 1998). If they had, this would have had all the hallmarks of a situation that might provoke a true identity crisis. Similar observations have also been made with cross-fostered monkeys. Thus there are really no grounds for the concept of "the ugly duckling", "a fish afraid of water" or "an owl frightened by darkness".
Some final conclusions
Awareness of self may be very limited in other animals
Ability to empathise with others' thoughts and feelings may also be limited
Only some great apes and dolphins recognise themselves in the mirror
This may be more a recognition that - "that is the same as me" than "that is me"
There may be something special about the way a human brain achieves theory of mind
Perhaps other animals can approximate to this through generating action-replay imagery
Perhaps the lack of theory of mind is why other animals have retained sophisticated senses for detecting emotional and psychological states in others.
With a limited self-concept or ability to conceive of others as holding different views, other species cannot develop an identity crisis.
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