How Many Friends Does One Person Need? (20 page)

We have, I think, to be a bit dissatisfied with this conclusion. It’s a bit like being handed a detailed summary of all the bricks, mortar, slates, wood and windows that make up a house, but without the breath of a mention of what the building itself looks like or why it’s there. Or being given a detailed account of all the bits and pieces under the bonnet of a car, but not a word about how they function to propel the car along the road or why one might even want to do that. To me, that smacks a bit of trainspot-ting – making endless lists of engine numbers without taking the trouble to ask what trains are actually there for.

In fact, there is reason to think that at least some of the monkeys and apes are a bit different from the run-of-the-mill mammal and bird. It’s their ability to handle social complexity that seems to mark them out, and this seems to depend on a peculiar kind of cognition that has come to be known as ‘social cognition’. Monkeys and apes seem to differ from other animals in the intrinsic complexity of their social relationships. The important thing here is not that they can do certain kinds of behaviours that others cannot, but rather
how
they do them.

Primates engage in forms of behaviour that are unique
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and do not occur in other non-primate species, as for example Dick Byrne and Andy Whiten’s study of ‘tactical deception’ showed.
*

*
See Chapter 3

The important issue seems to be that they are able to appreciate how what they do will be mis-interpreted by the other individual, and thus result in that individual behaving in a way beneficial to the actor.

The idea that monkeys and apes read minds (like humans do) rather than just behaviour (like all other species seem to do) has, however, faded somewhat with time. There is simply no evidence that any primates other than humans have a generalised capacity in this respect. Indeed, the only evidence for any kind of nonhuman mind-reading is from great apes. Even so, the evidence is not straightforward. While there is a lot of experimental evidence to show that chimpanzees can understand another individual’s perspective, evidence that they have full-blown theory of mind is more equivocal. One study found that chimpanzees failed the critical kind of mind-reading task (the ‘false belief’ task) that young children pass with ease, while a second study showed that, although chimpanzees did do better than autistic humans (who definitively lack mind-reading capacities), they only did about as well as normal four-year-old children (who are in the process of acquiring mind-reading capacities, and so only have this skill imperfectly). It was this ambiguity that led Cartmill and Byrne to try a different tack with their orang utans.

Despite this, there is something very intense and personal about the social relationships of monkeys and apes that marks them out as very different from the kinds of relationships exhibited by other species. So far as I can
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see, the only real exception in this respect seems to be domestic dogs, who seem to have been bred explicitly to exhibit the same kind of intense social commitment that primates have. Whether dogs’ capacity to behave in this way is merely a superficial behavioural analogy of monkeys’ capabilities or whether they produce these behavioural effects using the same kind of underpinning psychological mechanisms remains to be seen.

Nonetheless, these mind-reading abilities seem to give us some purchase on just what the differences between humans and other animals actually are. Intentionality is the capacity to reflect on the contents of one’s mind, as reflected in the use of verbs like
suppose
,
think
,
wonder
(whether... ),
believe
, etc. The capacity to use these words defines first-order intentionality: such an animal is capable of knowing its own mind. Most mammals and birds probably fall into this category.

More interesting are those cases in which the individual is capable of reflecting on someone else’s mind state:
I suppose that you believe
. . . That capacity defines a higher level of intentionality, conventionally referred to as second order. It is equivalent to the stage that children achieve at about the age of five when they first acquire theory of mind. More interesting still is whether this sequence can be extended reflexively to yet higher orders. We have shown experimentally that normal adult humans can aspire to fifth-order intentionality as a matter of course, but that this represents a real upper limit for most people. Fifth order is the equivalent of being able to say:
I suppose
[1]
that you
believe
[2]
that I want
[3]
you to think
[4]
that I intend...
[5] (with the successive orders of intentionality marked out in square brackets).
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The hierarchical nature of intentionality provides us with a natural metric for scaling species’ social cognitive abilities. If humans have a limit at fifth-order intentionality, chimpanzees (and perhaps other great apes) at second order, and monkeys at first order, then it turns out that these capacities are a linear function of the relative size of the frontal lobe of the brain (and only of the frontal lobe). This is interesting for two reasons. One is that the brain (and particularly the neocortex, the thin outer sheet that is both a mammal speciality and the seat of most of the complex behaviours we associate with ‘thinking’) has evolved from back (the location of the visual processing areas) to front. The frontal lobe is particularly associated with those capacities that psychologists refer to as ‘exec-utive function’ (in very crude terms, conscious thought). Second, large neocortices in general (and large frontal lobes in particular) are a primate speciality, suggesting that whatever psychological capacities are underpinned by these neural structures are likely to be especially well represented among (if not unique to) primates.

So what are these capacities that monkeys and apes have?

In my view, it is not so much the capacities that differ between monkeys, apes and humans, but the scale at which each species can exercise these individual capacities. These capacities are in fact those basic to the lives of all mammals and birds. Minimally, they include the ability to reason causally, to reason analogically, to run two or more models of the world simultaneously, and the length of time into the future that any such model can be run. When these individual capacities are brought together on a large enough scale, mind-reading pops out as an emergent prop-
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erty. It looks like something special, and in one sense it genuinely is, but it is not some kind of specialised primate or even human capacity. Rather, it is the capacity to do better what everyone else does. In short, the differences between the various species of mammals on the scale of rats to humans is simply one of what might be termed the computational advantages of scale.

Despite this, the mind that has given us poetry as well as modern science sometimes seems incredibly limited. One example of this is the fact that we so often seem to make do with simple dichotomies. We are ‘for or against’, ‘on the left or the right’, ‘beyond the pale’ (as opposed to within it), ‘friend or foe’. And it’s not just English-speakers that go in for these simple views. Like many traditional peoples, the San bushmen refer to themselves as
Zhu/twasi
–meaning ‘real people’ as opposed to the rest of them.

Which set me thinking. We seem to have an awful lot of these dichotomies in science. There is the well-known debate on the nature of light, for example. Is it really waves as the Newtonians supposed, or is it made up of particles (in the form of photons) as the quantum theorists argued? Then there was the great debate among the nineteenth-century geologists, between the ‘catastrophists’ and the ‘uniformitarians’. The catastrophists followed the influential French taxonomist Baron Cuvier in arguing from the geological evidence that dramatic changes in the environment, such as floods and volcanic eruptions, led to the complete extinction of certain forms of life and their subsequent replacement by entirely new ones.
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Uniformitarians, such as the eminent British geologist Sir Charles Lyell who was one of Darwin’s mentors, insisted that the geological record showed gradual change, with a correspondingly gradual evolution of life forms.

Comparable debates occurred in physiology. In the mid-nineteenth century, the physicists Thomas Young and Herman von Helmholtz between them developed the familiar ‘trichromatic theory’ of colour vision, a view that gained credence from the discovery that the retina of the eye contains just three types of cells that respond to colour, one for each of the ‘primary’ colours (red, green and blue) identified by the physicists. A few decades later, however, the German physiologist Ewald Hering developed the so-called ‘opponent colour theory’ on the basis of experiments which suggested that the visual system perceives colours in terms of complementary pairs – blue/yellow and red/green. What is perhaps more interesting than the dichotomies is the fact that the often vitriolic debates that have accom-panied them were eventually resolved when someone pointed out that both theories were in fact right. Light does behave like both waves and particles on different occasions, and the choice may be as much a matter of analytical convenience as of underlying reality. Similarly, evolution does proceed at different rates at different times. Volcanic eruptions or comet impacts do force the pace by causing mass extinctions, but at other times evolution proceeds at a more leisurely rate with a steady turnover of mutations. And the two theories of colour vision turn out to apply at different levels within the visual system: the retina analyses light according to the three-colour theory, but the visual cortex does so according to the four-colour
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version.

Nor are these examples unusual. The way in which mammals perceive sound long provided the basis for an acrimonious argument between the ‘place’ and ‘frequency’ theorists. One group argued that the pitch of a sound is determined by how far up the organ of Corti the vibrations transmitted by the cochlea travel;
*
their opponents argued that it was the frequency with which the organ itself vibrated that determined the pitch. In fact, both theories are right: for good physical reasons, low-pitched sounds are analysed on the basis of frequency, while high-pitched ones are analysed on the place theory.

*
The organ of Corti is a highly sensitive membrane in the inner ear. The twenty thousand or so fine hairs that attach it to the fluid-filled compartment of the cochlea register the sound waves transmitted from the ear and turn them into nerve signals to the hearing centres in the brain.

We’ve even had the same kind of disputes in mathematics. In 1764, the Reverend Thomas Bayes, an English Presbyterian minister and Fellow of the Royal Society, published a posthumous paper in which he sketched out a theory of probability based on confidence. It was an elegantly simple theory based on a single mathematical theorem that could be applied under any circumstances. But later mathematicians baulked at his ideas, preferring something that was more firmly rooted in observable facts: they argued that probability is better defined as something about the frequencies with which events (such as tosses of a coin) happen. Thomas Bayes and his theorem fell into obscurity. But the last laugh was on Bayes: it turns out that the frequency theory of probability is really just a special case of his theorem about confidence.

Then there is that old chestnut of ‘nature versus nur-
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ture’, which reappears with such monotonous regularity as almost to count as a law of nature itself. And every time it reappears, it is resolved in exactly the same way. In the 1940s, nature versus nurture was the focus for the debate over the inheritance of IQ; later, in the 1950s, it resurfaced in ethology in the debate about the nature of instincts; then in the 1970s, it resurfaced in the even more vitriolic but no less muddled controversy that grew up around sociobiology. And it resurfaced again in the 1990s with the appearance of evolutionary psychology and the rather predictable response to that from the social sciences and parts of mainstream psychology. And each time someone eventually remarked that we cannot separate genetic from environmental influences in the development of organisms in so simple a fashion, even though, like waves and particles in light, it is sometimes convenient to talk of one to the exclusion of the other.

Our problem is that our minds just lack the intellectual capacity to deal with continua, especially if these continua involve the interaction of several variables operating along different dimensions. We are happiest with simple dichotomies because they save us having to think. Although evolution has no doubt provided us with a satisfactory rule of thumb for getting by in everyday life, thinking in dichotomies becomes increasingly unsatisfactory for handling the complexities beneath the surface that are the real stuff of science. Knowledge, it seems, is perpetually threatened by our own intrinsic limitations.

Well, I’m still waiting for some enterprising chemist to resurrect Joseph Priestley’s phlogiston theory of combustion by showing that it is complementary to the oxygen theory that we owe to his arch rival, the Frenchman
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Antoine Lavoisier. Lavoisier – who ended up on the guil-lotine for being one of Louis XVI’s tax collectors – argued that things burn by consuming oxygen from the air, whereas Priestley (and pretty much everyone else at the time) claimed that when things burned they gave up a substance called phlogiston. Lavoisier used his skills as an accountant to show that things got heavier, not lighter, when they burned up, and so must have taken in something, not given it up, thereby paving the way for the modern atomic theory of chemistry. It’s never likely to happen, of course; still, one has to wonder whether as great a chemist as Priestley could have been all wrong...

And here’s another example of our sometimes distressing inability to think things through properly. Some years ago in the days before email, my Monday post brought a large brown envelope. To my surprise, it contained a request to take part in a chain letter. ‘Send no money!’ it said. Just send copies of this message on to five other friends and colleagues within four days and ask them to do the same. ‘If you don’t,’ it went on ominously, ‘bad luck will befall you.’ Simple as that.