In the latest issue of Scientific American, I have a feature on the biology of intelligence. (Read it online at sciam.com or carlzimmer.com) I’ve been fascinated by the subject for a long time, and I decided recently that the time was right to put together an article.
What’s the news? That there is no news.
Allow me to explain…
A lot of experts on intelligence were very busy late last year trying to clear up some misconceptions about the nature of intelligence in the wake of Nobelist James Watson’s remarks about race and IQ. (The best example I came across at the time was an hour-long discussion that aired in December 2007 on the show On Point. You can listen to it here.) It would be a mistake, however, to conclude that there is no such thing as intelligence–by which I mean something that scientists actively study, testing hypotheses and finding significant results. Intelligence tests do identify a difference among people that has predictive power, and that difference can be linked–in part–to differences in people’s genes.
The news about intelligence is that now scientists have new tools for probing intelligence, from brain scans to gene chips that can search for variations in half a million genetic markers at a time. But so far, those tools are yielding some pretty scant results. For example, just a handful of genes show much sign of influencing intelligence, and yet each one accounts at best for a fraction of one percent of the variation in test scores.
It may not be fashionable to write about the lack of breakthroughs, but in a case like that of intelligence, that’s what fascinates me most. I’ll be curious to hear what others think.
—Update: Where are my manners? For those who want to head for the primary literature, here are two key papers:
Butcher et al, Genome-wide quantitative trait locus association scan of general cognitive ability using pooled DNA and 500K single nucleotide polymorphism microarrays Genes Brain Behav. 2008 June; 7(4): 435–446. (Free full text)
Jung and Haier, The Parieto-Frontal Integration Theory (P-Fit) of intelligence: converging neuroimaging evidence, Behav. Brain Sci. 2007 Apr;30(2):135-54 (Download free pdf here)