The embedding is going to be tricky here.
At 04:57 PM 11/21/98 +1100, Tim quoted before commenting:
>Mikey said
>>I would say that since women have a dominant right brain, while men are
>>dominant left,
>
>Patrick wrote
>>How do you come at this? I wasn't aware there was any good evidence
>>differences in lateralization between men and women that contributed to
>>cognitive style. [Any references?]
>
>Dozens.
Observe the shift in meaning. Mike said that men and women have contrary brain dominance (undefined). Patrick asked about the impact on cognitive style of lateralization.
>One reason that there is less on this than one might expect is that
>interest in this topic tends to generate the response that Damien was
>driven to emit, i.e.:
>
>>What? *What????* WHAAAAH
>
>Not conducive to getting grants or publishing work.
My horrified yelp might have been more explicit, it's true. :)
But I wasn't emitting a cry of amazement at the results, but rather a shocked cry at the original claim (as I had read it) being made by an intelligent and informed person. Mikey's claim didn't deal with minor lateralisations but with DOMINANCE. This is not well-defined, I think, but seems to be a rough-and-ready way of indicating which hemisphere houses the main language-processing modules, construed as the locus of awareness, intention, self, something like that (see Gazzaniga, below). That notion in turn reflected the work in the 1960s on cutting the corpus callosum and finding that each hemisphere then showed quite distinct specialties, normally hidden by the ceaseless cross-lobe interactions of the healthy brain. The `left-brain' was found to be `dominant' for language use and abstract reasoning in most humans. Since we're such political animals, the word `dominance' instantly blurred into a general belief about which side of the head was in charge.... boss of the soul, as it were.
You can see how an unconsciously sexist culture quickly read this garbled claim backward into support for its unpleasant ideology. Traditionally, men are rational, articulate, focussed, while women are intuitive blurry babblers. Wow! Maybe that's because men are dominant in their left hemisphere, women in their right. U.s.w. Meanwhile, research was indeed showing small differences in lateralization between male and female populations, which seemed to support that zany (and mischievous) misunderstanding. (It is potentially mischievous in a number of directions. Male supremacists can use it to shove women back inside the house, as the Taliban do. Varieties of feminism can use it to argue that `women's consciousness' is holistic and sui generis.)
Actually, the differences between men and women in respect of any general `dominance' are insignificant compared to what is held in common. To cite Michael S. Gazzaniga, who did much of the work on split brains, `The idea of modularity is central to modern cognitive neuroscience... we now see that only the left hemisphere has the underlying brain organization which allows for high-level consciousness and belief formation' (NATURE'S MIND, Penguin, 121).
As for handedness and speech lateralization, Christine Temple's popular treatment THE BRAIN (Penguin 1993) offers some useful data. 98 percent of RHers (male and female alike, naturally) have left-hemisphere lateralization for language. It's more complex for LHers. Right-hemisphere language dominance seems to be controlled by a single allele (Annett 1985). In any event, Milner (1974) suggested long ago that `in left handers or ambidextrous individuals, in whom there is no evidence of left-hemisphere damage, approx. 70 % will have left-hemisphere speech representation' (Temple 100).
These data might now be out of date, but the only important new work I recall reading shows that women seem to be somewhat better cross-linked than men. The suggestion that women are `right-brain DOMINANT', however, is as absurd as suggesting that most women have their feet on backwards, or perhaps that their internal organs are enantiomorphic to the male. It is also dangerous, since as I noted above such claims are readily conscripted to malign ideological purposes.
Of course I do not wish to imply that anyone on this thread is arguing from those sorts of malevolent or self-serving motives.
Damien Broderick