Wolfgang has raised a point that I started to post several times, but the computer ate unsubmitted.

The work on strong lateralisation as an efficient means of organisation of the brain was done, I believe, some time ago, on a sample of volunteer male students at a university, I think in the US. (My sources, I am afraid, are long forgotten, but are probably New Scientist, with a second choice of Scientific American). It is possible that the sample was of a particular type of male - if mostly scientists, there would have been a higher proportion of autistic spectrum condition than in the normal populace (one suggestion for a cause of this has been a failure of communication between the two sides of the brain)- if mostly sportsmen, maybe another type of bias. These apparent irrelevancies may not be. The work discovered strong lateralisation, which was explained as a good way of working well, by locating resources close together. When work later extended to left-handed individuals, this correlated well with observed weaknesses in language development in the new sample.

Unfortunately, when women's brains were studied (and this is not new work), it was found that the language areas were not strongly lateralised, and that both sides of the brain were involved in various parts of language processing, more like left-handers than the original male sample. But it was already known from other studies that females develop language earlier, and maintain greater skills with language throughout development, so that the original lateralisation argument was shown to be less convincing.

It was then suggested that the differences between the two types of brain depended on the early development of language in the female, which allowed both sides of the brain to be used for language. By the time males started to develop these skills, they had already begun to develop spatial skills, using parts of the brain that the females had already used for language.

As in a lot of the differences between men and women, apart from the obvious and crucial primary and secondary characteristics, there is a lot of variation within the sexes. It begins to look as if it is not differentiation within one brain that matters, but the variety of different styles of differentiation across the population at large that is important. To identify very distinct types of difference by gender, and then use them as characteristics to knock the other by (after discovering the way that women's brains are organised, it suddenly became appropriate to knock their spatial skills, rather than praise the language skills) is not worth the effort.

Penny