There’s no hiding prejudice from your own subconscious or, for that matter, from the Implicit Association Test (IAT), an exam that can elicit biased feelings from even the most self-proclaimed tolerant among us. While it’s clear how prejudice appears in social settings, little has been known about how it occurs in the brain, until now.

In a recent study, researchers from the University of Bern in Switzerland used the IAT in conjunction with brain scans to better understand the bias. Word association tests like the IAT have long been used to show how different target words can be perceived as either positive or negative depending on the person’s prejudice. That’s because it usually takes longer for a person to associate a target with a positive attribute when they’re already prejudiced against it.

Researchers tested this effect on 83 participants who considered themselves soccer fans or political supporters. Each completed an IAT that involved clicking a button whenever a positive term appeared on the screen. The catch, however, was that each of these terms was associated with either an “in-group,” such as the preferred soccer team or political party, or an “out-group” — an opposing team or party. As participants clicked the button, their brain activity was scanned with an electroencephalogram (EEG).

Dr. Lorene Gianotti, a co-author of the study, said her team was able to create a “microstate analysis,” which mapped out brain activity among the participants while they completed their tasks. “It enabled us to depict all processes in the brain for the first time — from the presentation of a word up to pressing the button — temporally and also spatially," she said in a press release.

It took less than a second for participants to go from seeing each word — no matter its association — to clicking the button. During this time, the EEGs showed all participants’ brains completed a total of seven processes. This goes against the idea behind IAT, which is that prejudiced feelings cause the brain to take longer to respond because it requires the use of extra processes. Instead, the researchers found there were simply delays within these seven processes, caused by the hesitation from prejudice.

While the findings do not change what we already know about prejudice — that it’s both innate and automatic — they show the neurological underpinnings behind it. And in the study of human behavior, Knoch says understanding these processes is essential to gaining new insights.

Source: Schiller B, Gianotti LRR, Baumgartner T, Nash K, Koenig T, Knoch D. Clocking the social mind by identifying mental processes in the IAT with electrical neuroimaging. PNAS .2016