Not surprisingly, we tend to hear the most about bigotry and prejudice when it surfaces explicitly: see Oprah Winfrey's recent experience in a high-end Swiss boutique, for example, or the New York police department's stop-and-frisk policies, ruled racially discriminatory by a judge this week. But the truth is that much prejudice – perhaps most of it – flourishes below the level of conscious thought. Which means, alarmingly, that it's entirely possible to hold strong beliefs that point in one direction while demonstrating behaviour that points in the other. The classic (if controversial) demonstration of this is Harvard's Project Implicit, made famous in Malcolm Gladwell's book Blink. You can take the test here: whatever your race, there's a strong chance you'll take a split second longer to associate positive concepts with black faces than white ones.

Two recent pieces of research underline just how ubiquitous this kind of bias could be. One survey, reported at Inside Higher Education, involved asking white people in California how they felt about meritocracy as the basis for college admissions. The argument in favour of meritocracy, of course, is often used in opposition to affirmative action, which gives extra weighting to black students' applications. But if white Californians backed meritocracy out of pure principle, you'd expect their beliefs to hold firm no matter what race they were thinking about. Yet when you phrase the question so as to remind them that Asian American students are disproportionately successful at getting into Californian colleges, their support for meritocracy wanes.

The implication is that for at least some people, belief in meritocracy is flexible on racist grounds: it's drafted in when it helps justify white students' advantages over black ones – but it suddenly grows weaker when it risks justifying Asian American students' advantages over white ones. The urge towards system justification is strong.

A study published earlier this year is even more unsettling: it suggests that if you fail to challenge someone who expresses prejudiced attitudes, you'll actually become more prejudiced yourself. Researchers engineered a situation in which female participants heard a male experimenter make a sexist remark; some were then given the opportunity to call him out on it. Eric Horowitz explains the scenario:

In each experiment, female participants first rated their beliefs about the importance of confronting prejudice and then engaged in a “Deserted Island” task with a confederate. The task involved selecting from an existing set of people those who would be most helpful on a deserted island. The confederate … chose all males until his final selection, when he justified his choice of a female with a sexist remark (“She’s pretty hot. I think we need more women on the island to keep the men satisfied.”)

Those who had the chance to challenge this remark, but didn't do so, rated the experimenter as less sexist – and challenging sexism as less important – than the others. Which would seem to be a case of cognitive dissonance in action: when you're confronted by prejudice and you don't object to it, your own attitudes shift in a more prejudiced direction, to maintain consistency between your behaviour and your beliefs.

And then there's the finding that more intelligent white people are more likely to disavow racism, but no more likely actually to support policies that might remedy the effects of racial inequality. This news was reported as showing that clever people are just better at concealing their racism from others while harbouring bigoted thoughts. But isn't the more worrying possibility that they're concealing their racism from themselves?

Or to put it another way: those of us who reassure ourselves that we're implacably opposed to prejudice could probably do with being a lot less smug about it.