What sets us apart from other species

Earlier this year, the Royal Institution invited the philosopher AC Grayling, along with Igor Aleksander, professor of neural systems engineering at Imperial College, London, and the historian Felipe Fernandez Armesto, to discuss the question ‘What makes us human?’ Igor Aleksander claims to have built a robot that has consciousness – he was there to address the ways in which human intelligence differs from artificial intelligence. Fernandez Armesto has written a book called So You Think You’re Human? He was defending his claim that there are in fact no great differences between humans and other animals.

The debate soon became a wrangle between the historian and the philosopher. Grayling held that Fernandez Armesto’s argument was based on a mistake: just because some concepts like ‘animals’ and ‘humans’ have fuzzy edges, it does not mean there are not clear and very significant differences between them. One of the arguments Grayling used to defend his position was that humans’ use of language is a significant difference between humans and other species.

Robin Dunbar’s lecture at the 2004 Edinburgh International Book Festival on his new book, The Human Story starts closer to the position that Grayling held during that debate. However, he does not say that language is the area of greatest difference. Dunbar is professor in evolutionary psychology and behavioural ecology at Liverpool University. His tenet is that the significant difference between us and other species is the larger size of our brains. In his book he speculates, ‘what sets us apart is, above all, a life in the mind, the ability to imagine’.

Compared to the great apes, we have an ability to imagine a complex future. We are a species that constantly reasons, deduces, guesses and speculates about what might happen and about the behaviour of others in relation to ourselves. The great apes can only predict future events and, crucially, the behaviour of other apes, to a limited degree. Echoing Schopenhauer’s notion of a ‘world of perception’, Dunbar said that animals ‘have their noses thrust up against the grindstone of the world’.

In his 2003 book What Is Good?, Grayling outlines Kant’s approach to the same question: ‘Human beings are, figuratively speaking, halfway between the animals and the angels in the sense that they have both reason and the full complement of animal appetites and instincts’. But Kant thought this very struggle allowed humans to grasp the concept of morality. He thought that moral value was based on an individual acting out a sense of duty to obey a moral law, identified by that free individual’s reason as the only appropriate response in the circumstances.

There is a common idea here, shared with Dunbar, that it is something about our mind and our use of it to live among other people that sets us apart from animals. Whilst Kant thought it was our reason, and by implication, our moral sense, Dunbar thinks the difference is specifically in the use of our minds to imagine what people might do and thereby anticipate strategies that contribute to social cohesion.

But what is the evolutionary advantage of these capacities of prediction? Our brains are expensive to run. They take up only 2% of our body weight, but maintaining the functioning state of the nerves in the brain costs 20% of the food we eat. Clearly, for our brains to be so large, and so expensive in terms of fuel, they must have an important function. Dunbar proposes that it is our large brains that enable us to predict the motives of others and construct strategies for dealing with them, thereby enabling social cohesion and an efficient, co-operative society.

But why link the brain with social interaction and the ability to predict other peoples’ motives? The answer might lie in the uncanny relationship between the size of the neocortex and the size of social groups. The neocortex is the largest part of the brain – the part we use to think, as distinct from the parts that control our bodies’ mechanisms. Its size correlates almost exactly to the size of each species’ social group. In humans, the average size of the social group is about 150 individuals, that is, the number of people you know as individuals or the number of people who would be likely to do you a favour. It is also that number of individuals within households to which you might send Christmas cards: people who would know how they fit into your social world and you into theirs. In contrast, chimps have a social group size of approximately 50 individuals. We begin to see a link between brain size and social interaction.

But how does the ability to predict motives figure in this relationship between the size of the neocortex and social grouping? Cue theory of mind – the realisation that other people have minds like oneself, and may indeed hold different points of view. Great apes share this characteristic with us, albeit to a more limited degree. Humans develop this ability by the age of four.

At this age, we see theory of mind exemplified by the child’s ability to engage in pretence and in the ability to lie convincingly. Dunbar cites the ‘Sally-Ann false belief task’ to illustrate the point. A child of about four is shown two dollies, Sally and Ann. The child is told that Sally has a ball in her basket and that when Sally isn’t looking, Ann takes the ball and puts it under a box. The child is asked where Sally thinks the ball is. The child above four years demonstrates theory of mind by saying that Sally thinks the ball is in the basket. The child has demonstrated that, given reason for doing so, another individual may hold a different point of view to oneself – even a false belief. For this reason this type of task is known as a false belief task. Before the age of four, children know that adults will believe them if they try very hard to convince them of such and such a fact – but they don’t know why.

Researchers have been able to prove that some animals have a theory of mind at this basic level by devising non-verbal tests that prove the point. When asked what kinds of tests were used, Dunbar explained one used on dolphins, but highlighted the difficulties encountered. One such problem mentioned in his book is the famous ‘Clever Hans’ effect. Clever Hans was the German horse who could count – he would tap out the answer to simple sums with his hooves. As it turned out, when Hans reached the penultimate tap of the hoof, his trainer betrayed an involuntary cue – he instinctively nodded his head – and this told Hans that on the next cue if he stopped tapping he would be rewarded.

The dolphins picked up on a similar cue during the false-belief tasks. At first, the researchers thought that they had managed to demonstrate theory of mind in dolphins, only to realise they were encountering not only the ‘Clever Hans’ effect, but that the dolphins would also try and hedge their bets: not only would they point with their beaks to what they thought might be the correct box used in the task, but they would also drift across the tank towards the neighbouring box. Perhaps the dolphins really did exhibit theory of mind in realising they could manipulate the goodwill of the researchers in giving them the benefit of the doubt. Or perhaps it really was just a ‘Clever Hans’ effect and they simply realised that if they drifted they were more likely to be rewarded.

So where do humans stand compared to the great apes regarding theory of mind? Unlike chimps, we are able to extend our understanding to imagine the mental states of not one, but several individuals in a given scenario. At this point we need to introduce the idea of what is known in philosophy of mind as ‘intentionality’ – the state of being aware of the contents of your own mind. Dunbar defines it as ‘the kinds of mental states that we have when we are conscious of holding some kind of belief, desire or intention… in this scheme of things, computers are zero-order intentional entities: they are not aware of the contents of their ‘minds’. Some living organisms such as bacteria (and perhaps some insects) may also be zero-order intentional beings’.

There can, however, be a hierarchy of intentionality. An example of first order intentionality is awareness of hunger, or of a threat. Most animals appear to demonstrate first order intentionality. The same is true of autistics, who lack the ability to empathise with others and are incapable of lying. Theory of mind, therefore, equates to second order intentionality – an awareness of your own, and someone else’s mind and that their mental states (eg beliefs) may be different from your own.

Human adults can manage about five or six levels of intentionality ie ‘Peter believes (1) that Jane thinks (2) that Sally wants (3)… etc. A core social group consists on average of 10-15 individuals, and Dunbar explained that, interestingly, the more levels of intentionality a person can demonstrate, the larger the core social group. Unsurprisingly, women, with – according to research by Simon Baron Cohen – a greater ability to empathise than men, are often able to demonstrate more levels of intentionality than men. As Dunbar says in the book ‘for a girl, relationships are often so intense and focused that not being invited to Penelope’s party is little short of the end of the world; for boys of a similar age, a relationship largely involves kicking a soccer ball back and forth across a street – a wall would do almost as well as another boy, providing it returned the ball.’

The major difference between our brains and those of the great apes would appear to be the ability to imagine not just another’s point of view, but those of several people. But if we foster social cohesion through being able to grasp the states of mind of several individuals in a group, and to express our thoughts in language, how do great apes achieve the same thing?

Commitment and social bonding among in primates is fostered through grooming. The low-level, repeated tactile stimulation of grooming releases endorphins, triggering a natural high. These opiate surges ensure the individuals are relaxed and contented – ideal conditions for social cohesion. But grooming is labour intensive – a one to one activity. Perhaps in humans, language replaced grooming as a form of social cohesion. Language is not necessary for an individual to possess a theory of mind, but it probably does become necessary in order to express strategies for acting upon the scenarios involved in managing several levels of intentionality.

Sadly there was no time in the talk to explore any relationship between language and intentionality. Language doesn’t produce the same opiate effect as grooming, but it is more effective in communicating with the larger number of individuals found among human groups. Singing, laughter and music, all do, however, produce similar physical effects to grooming. It is well known that religious people live longer than non-believers, besides enjoying better mental health, falling ill less frequently and recovering more quickly. We were left with a final speculation that perhaps religion originated from communal singing.

Dunbar’s argument outlined that groups form in order to solve a problem of ecology or survival, but in order to do so, there needs to be a trade-off between the perceived benefits now and later. Our brains and those of great apes have a mechanism called theory of mind – the ability to grasp what another might be thinking. But human brains are more costly to run than those of the great apes, besides being much larger, and we see a correlation between this fact and the sizes of the respective social groups. In contrast with the great apes we developed beyond grasping a theory of mind, to being able to demonstrate up to six levels of intentionality. If, from this, we are able to predict what others might do we can take measures to foster social cohesion, ensure group tasks are achieved and counter the behaviour, motives and strategies of freeloaders – parasitic individuals who live off the group.

Robin Dunbar is an accomplished, informative and interesting speaker. When necessary he didn’t shirk from explaining the rudiments of philosophy of mind to a mixed and unknown audience. Sadly, he was not specific about where his contribution lay in this field and where it followed on from others, nor about rival views to his own. As outlined in his talk, his theory is optimistic. We predict the motives of others not just to contribute to social cohesion, but to cause strife, win territory and assume power. But a talk that manages to inspire a desire to explore the history of ideas about why we have larger brains than the great apes is sixty minutes well spent.


Credit : Felicity Graham

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