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a story about physical cause and effect or a series of unlinked sentences. In people with Asperger’s syndrome, however, this area does not light up when reading mental-state stories, but a neighbouring area does, instead. This is an area implicated in general reasoning, which supports the psychologists’ hunch that Asperger’s people reason about social issues rather than empathise about them.³⁹

      All of which rather supports the idea that Jamesian instincts must be manifest in mental circuits called modules, each specifically designed to be good at its specific mental task. Such a modular view of the mind was first enunciated by the philosopher Jerry Fodor in the early 1980s and later developed by the anthropologist John Tooby and the psychologist Leda Cosmides in the 1990s. Tooby and Cosmides were attacking the then widespread belief that the brain is a general-purpose learning device. Instead, said the anthropologist-psychologist couple, the mind is like a Swiss army knife. For blades and screwdrivers and things for helping Boy Scouts get stones out of horses’ hoofs, read vision modules, language modules and empathy modules. Like the tools of a knife, these modules are rich in teleological purpose: it makes sense not just to describe what they are made of and how they do their job, but what they are for. Just as the stomach is for digestion, so the visual system of the brain is for seeing. Both are functional, and functional design implies evolution by natural selection, which implies at least partly a genetic ontology. The mind therefore consists of a collection of content-specific, information-processing modules adapted to past environments. Nativism was back.⁴⁰

      This was the high point of what is sometimes called the cognitive revolution. Though it now owes much to the tragic genius Alan Turing, with his extraordinary mathematical proof that reasoning could take a mechanical form – that it was a form of computation – the cognitive revolution really began with Noam Chomsky in the 1950s. Chomsky argued that the universal features of human language, invariant throughout the world, plus the logical impossibility of a child deducing the rules of a language as quickly as it does merely from the scanty examples available to it, must imply that there was something innate about language. Much later, Steven Pinker dissected the human ‘language instinct’, showed it had all the hallmarks of a Swiss army knife blade – structure designed for function – and added the notion that what the mind was equipped with was not innate data, but innate ways of processing data.⁴¹

      Do not mistake this for an empty or obvious claim. It would be quite possible to imagine that vision, language and empathy are done by different parts of the brain in different people. That indeed is the logical prediction that follows from the empiricist argument that runs from Locke, Hume and Mill right up to the modern ‘connectionists’ who design multi-purpose computer networks to mimic brains. And it is wrong. Neurologists can produce battalions of case histories to support the idea that particular parts of the mind correspond to particular parts of the brain with very little variation all over the world. If you damage one part of your brain, in an accident or after a stroke, you do not suffer some generalised debility: you lose one particular feature of your mind – and the feature you lose depends precisely on which part of the brain is lost. This cannot but imply that different parts of the brain are pre-designed for different jobs, something that could only come about through genes. Genes are often thought of as constraints on the adaptability of human behaviour. The reverse is true. They do not constrain; they enable.

      True, there have been rearguard actions by the retreating empiricists, but these skirmishes have only briefly delayed the advance of the modular mind. There is a degree of plasticity in the brain that allows different areas to compensate for the failure of their neighbouring area. Mriganka Sur has partly rewired the eyes of a ferret to the auditory cortex of its brain rather than the visual cortex, and in some rudimentary way it can still ‘see’, but not very well. Although you might think it remarkable that the ferret can see at all after such surgery, there is disagreement whether Sur’s experiment reveals more about the plasticity of the brain or the limits of that plasticity.⁴²

      If the modular mind is real, then all you have to do to understand the special features of the human mind is to dissect the brain to find out which bits have ‘hypertrophied’ in the past few million years—which modules and therefore which instincts are disproportionately big. Then you will know what makes human beings special. If only it were so easy! Almost everything in the human brain is bigger than in the chimpanzee brain. Human beings apparently do more seeing, more feeling, more moving, more balancing, more remembering and even more smelling than chimps. Far from finding a normal chimpanzee brain with a huge, turbo-charged thinking-and-speaking device attached to it, you find, if you look inside the human skull, more of everything. Closer inspection reveals that there are certain subtle disproportions. In primates generally, compared with rodents, the bits that do smelling have shrunk dramatically and the bits that do seeing have grown. The neocortex has grown at the expense of the rest. But even here the disproportion is not very marked. Indeed, since the neocortex develops last, and the frontal regions last of all, you could simply explain the big human brain as a chimp brain that has been grown for longer. In its extreme form this theory holds that the brain expanded, not because expansion was demanded by the requirement for it to do new functions – specifically language or culture – but because something required the enlargement of the brain stem itself and a bigger cortex came along as a passenger for the ride. Remember the lesson of the IQ domains in the ASPM gene: it is genetically easy just to make every part of the brain bigger. Once the big brain was there, hey presto, 50,000 years ago, Homo sapiens suddenly discovered he could use it to make bows and arrows, paint cave walls and think about the meaning of life.⁴³

      This idea has the advantage of again taking the species down a Cartesian peg – away goes the reassuring notion that humankind was the subject, rather than the object, in its own evolutionary story. But it is not necessarily incompatible with the idea of a modular mind. In fact, you could just as easily turn the logic on its head and argue that human beings were under selective pressure to develop more processing power in the parts of the brain needed for one function – language, say – and the easiest way for the genome to respond was to build a bigger brain generally. The ability to do more seeing and have a greater repertoire of moves was thrown in free. Besides, even a language module is hardly likely to be isolated from other functions. It needs fine discrimination of hearing, finer control of movement in the tongue, lips and chest, greater memory, and so on.⁴⁴

      Scientific theories, however, like empires, are at their most vulnerable when they have vanquished their rivals. No sooner had the modular mind triumphed than one of its main champions started dismantling it. In 2001 Jerry Fodor published a remarkable little book called The Mind Doesn’t Work That Way, which argued that though breaking down the mind into separate computational modules was by far the best theory around, it did not and could not explain how the mind works.⁴⁵ Pointing out the ‘scandalous’ failure of engineers to build robots capable of routine tasks like cooking breakfast, Fodor gently reminded his colleagues how little had yet been discovered and chided Pinker for his cheerful optimism that the mind was explained.⁴⁶ Minds, said Fodor, are capable of abducting global inferences from the information supplied by the parts of the brain. You may see, feel and hear raindrops with three different brain modules linked to different senses, but somewhere in your brain resides the inference: ‘it is raining’. In some inevitable sense, then, thinking is a general activity that integrates vision, language, empathy and other modules: mechanisms that operate as modules presuppose mechanisms that don’t. And almost nothing is known about the mechanisms that are not modular. Fodor’s conclusion was to remind scientists just how much ignorance they had discovered: they had merely thrown some light on how much dark there was.

      But at least this much is clear. To build a brain with instinctive abilities, the Genome Organising Device lays down separate circuits with suitable internal patterns that allow them to carry out suitable computations, then links them with appropriate

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