Harvard's IATs

Interesting tests. Does anyone know much about the principles behind them? I took the test on race, and it asked me to group pictures/words as quickly as possible. Pictures of faces had to be classified as African-American or European-American, while words had to be either good or bad. At times you had to group pictures and words simultaneously. (For example, in one round, good and European-American are represented by the same button, while in the next round it might be good and African-American.)

I assume that they are looking for some sort of hesitance, since the test instructs you to react as quickly as possible. For the record, I apparently have no racial preferences. But couldn't this just as easily be an indicator of my ability to sort rapidly and accurately? As a control of sorts, I took the test on religious preference. Unsurprisingly, Christianity was the religion I viewed most positively, followed by Judaism. However, Islam scored higher than Hinduism. Any conscious preferences I have between the two faiths definitely fall out in favor of Hinduism. This leads me to another thought. Perhaps our brains are quicker at sorting the familiar than the unfamiliar? While I may prefer Hinduism, I have far less experience with it, and am far less likely to be using Hindu terms in daily conversation. If my suspicion is correct, it seems like it might have a material impact on how we assess the results of the racial test as well. Thoughts?

For some discussion of these tests, look here and here.