A recent poll by Washington Post/ABC News showed that while Mitt Romney leads Barack Obama by 60% to 37% among white voters, Obama leads the challenger among 79% of non-white voters.
Of course there are many reasons other than race which contribute to this difference, but there can be little doubt that attitudes to race play a very significant part in this close electoral contest. This has been highlighted by the rumor and innuendo surrounding the supposed doubt about Obama's place of birth.
In May 2008, when Barack Obama and Hilary Clinton were slugging it out in a series of primaries for the Democratic nomination for the presidential election, E. Ashby Plant and colleagues from Florida State University discovered a quite remarkable change happening in the brains of a sample of US citizens.
They used a method for measuring unconscious or 'implicit' attitudes to race using a method called the Implicit Association Test, or the IAT. Plant and his colleagues used this method to study the implicit racial attitudes of non-black people in the context of Barack Obama's campaign for the Democratic Party presidential candidacy. They were puzzled to find significantly lower levels of unconscious prejudice against black people during the Democratic primaries than had previously been measured. The exposure to the positive example of a highly intelligent and effective black person in a pre-eminent position - Barack Obama - seems to have reshaped the unconscious attitudes embedded invisibly in the tissue of some brains.
That we are really talking about physical changes in the brain underpinning these attitudes, is shown by research by Elizabeth Phelps and her colleagues from New York University who showed pictures of black and white strangers to white people whose degree of racial prejudice they had measured in two ways - by giving them a standard attitudes questionnaire, or using the IAT to measure their unconscious bias.
Phelps used fMRI brain imaging to look at activity in the amygdala - a key brain area for emotions such as fear and anger. While conscious racial prejudice measured by the questionnaire was unrelated to the amygdala's activity in the brain, unconscious, implicit prejudice was strongly related to the amount of amygdala activity while the participants saw black rather than to white faces.
Conscious thought is slow and has a very narrow bottleneck, meaning that it is very hard to follow more than one train of thought at a time. Unconscious thought, on the other hand, is very fast and does not have the same bottleneck. For this simple reason, most of the time in the business of everyday life, what we do and say is much more controlled by implicit, unconscious processes than it is by conscious ones.
This makes it less surprising that how we think we feel about politics and race does not map well onto the activity in the parts of the brain that really count when it comes to predicting how we will behave in a given situation. Our unconscious, implicit attitudes, in other words, are probably a more accurate measure of what we really prefer, than what we consciously think and say to ourselves and other people.
But elections should force us to sit back and allow our slow, deliberative, conscious minds to weigh up who would do the best job as president. Democracy depends on rational, mature decisions and should not be shaped by unconscious, gut responses. But the polarization in US politics is such that this is probably a vain hope and race may be the trump card in the final result.