The Red Queen_ Sex and the Evolution of Human Nature - Matt Ridley [158]
If, indeed, we are the product of our nurture (and who can deny that many childhood influences are ineluctable – witness accent?), then we have been programmed by our various upbringings to be what we are and we cannot change it – rich man, poor man, beggarman, thief. Environmental determinism of the sort most sociologists espouse is as cruel and horrific a creed as the biological determinism they attack. The truth is, fortunately, that we are an inextricable and flexible mixture of the two. To the extent that we are the product of the genes, they are all and always will be genes that develop and are calibrated by experience, as the eye learns to find edges or the mind learns its vocabulary. To the extent that we are products of the environment, it is an environment that our designed brains choose to learn from. We do not respond to the ‘royal jelly’ that worker bees feed to certain grubs to turn them into queens. Nor does a bee learn that a mother’s smile is a cause for happiness.
The Mental Program
When, in the 1980s, artificial-intelligence researchers joined the ranks of those searching for the mechanism of mind, they too began with behaviourist assumptions: that the human brain, like a computer, was an association device. They quickly discovered that a computer was only as good as its programs. You would not dream of trying to use a computer as a word processor unless you had a word-processing program. In the same way, to make a computer capable of object recognition, or motion perception, or medical diagnosis, or chess, you had to program it with ‘knowledge’. Even the ‘neural network’ enthusiasts of the late 1980s quickly admitted that their claim to have found a general learning-by-association device was false: neural networks depend crucially on being told what answer to reach, or what pattern to find, or on being designed for a particular task, or on being given straightforward examples to learn from. The ‘connectionists’, who placed such high hopes in neural networks, had stumbled straight into the traps that had caught the behaviourists a generation earlier. Untrained connectionist networks proved incapable even of learning the past tense in English.13
The alternative to connectionism, and to behaviourism before it, was the ‘cognitive’ approach, which set out to discover the mind’s internal mechanisms. This first flowered with Noam Chomsky’s assertions in Syntactic Structures, a book published in 1957, that general-purpose association-learning devices simply could not solve the problem of inferring the rules of grammar from speech.14 It needed a mechanism equipped with knowledge about what to look for. Linguists gradually came to accept Chomsky’s argument. Those studying human vision, meanwhile, found it fruitful to pursue the ‘computational’ approach advocated by David Marr, a young British scientist at MIT. Marr and Tomaso Poggio systematically laid bare the mathematical tricks that the brain was using to recognize solid objects in the image formed in the eye. For example, the retina of the eye is wired up in such a way as to be especially sensitive to edges between contrasting dark and light parts of an image: optical illusions prove that people use such edges to delineate the boundaries of objects. These and other mechanisms in the brain are ‘innate’ and highly specific to their task, but they are probably perfected by exposure to examples. No general-purpose induction here.15
Almost every scientist who studies language or perception now admits that the brain is equipped with mechanisms, which it did not ‘learn’ from the culture, but developed with exposure to the world, that specialize in interpreting the signals that are perceived. Tooby and Cosmides argue that ‘higher’ mental mechanisms