FOR white liberals it threatens to be the ultimate embarrassment. A controversial brain imaging study published this week claims to have identified telltale signals linked to closet racial prejudice. It is one of a small but growing number in recent years which appear to indicate that brain science has advanced to the point where it can read our minds and lay bare our innermost prejudices. Can it really?
A century ago, racism was academically respectable. It was quite the fashion for scientists to go around measuring the craniums of peoples of different races in search of evidence of white superiority. These days magnetic resonance scanners have replaced the callipers of old, and the new goal is the mirror image of the old. Researchers no longer search black brains for evidence of intellectual inferiority. They search white brains for evidence of hidden racism.
Take the latest study, published in the journal Nature Neuroscience (DOI: 10.1038/nn1156). In it a team at Dartmouth College in New Hampshire scanned the brains of a group of white students while they viewed black or white faces. None felt they were racially prejudiced, but when presented with the black faces some of the students reacted with higher levels of activity in two particular brain areas near the front of the cortex. Not only that, but the stronger these brain signals were the more likely the student in the scanner was to have unwittingly revealed negative feelings about black people in word-association tests designed to probe concealed prejudice.
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The findings seem to raise the prospect of employers one day using 鈥減rejudice鈥� tests to screen job applicants, or of courtroom lawyers using brain scans to expose the racial biases of suspects or witnesses. In fact, any move in this direction would be misguided.
For a start there is a problem of false positives. Brain-scanning patterns that emerge from studying groups of people are hardly ever reliable enough to make accurate predictions about individuals. And that is the case here: by no means every student who produced strong brain signals displayed racial biases in the word-association tests.
A deeper problem is that it is not at all clear what these brain signals or association tests are really measuring. Psychologists probe for hidden racial biases by measuring how readily people associate race-related words with positive or negative words in computer tests. The study in the news, for example, found that some of the white students were slower at pressing a button to pair typical American black names, such as Tyrone, with positive words like 鈥渉ealth鈥� or 鈥渂eauty鈥� than they were at pairing the words with typically white names, such as Greg. This was said to mark them out as harbouring prejudices.
But as researchers commenting on the study have pointed out, there are plenty of other explanations. Some of the white students could simply have been reacting to the unfamiliarity of the black names: a previous study reported similar effects on reaction times when experimenters replaced the black names with nonsense letter strings. Or it could be that the tests are picking up on the fact that we live in a culture that engenders bias against blacks.
A study published last year found that not only do nearly all white people pair white names with positive words more readily than they pair black names with such words 鈥� most black subjects do as well. And brain scans too show the influence of culture. Previously teams reported a signal in the amygdala, a brain structure involved in registering fear, which only seemed to be present when white people looked at black faces. Tellingly, the signal vanished when the black faces were of well-known celebrities such as Michael Jordan.
It is even possible that some of these studies are detecting not closet racists but the very opposite: people who are aware of the politics of race and anxious not to be branded biased.
The new research is commendably provocative in its ambitions. In the end, however, brain scans read brains. They do not read minds, morals or culpability. Some experts and lawyers, especially in the US, have set out along the dangerous path of trying to bring brain imaging into the courtroom to bear on these questions. We must hope nobody goes down it clutching the idea that a couple of spots of extra activity in someone鈥檚 prefrontal cortex makes them a closet racist.
That really would be a thought crime.