First impressions matter, as the saying goes. They matter enough for researchers to dedicate their researching to figuring out how they’re formed in the brain. To this end, a team of psychologists and neuroscientists at NYU have correlated activity in two ares of the brain with first-time social evaluation.
The team set up a paradigm in which subjects, abed inside an MRI machine, were shown pictures of a face (all were male, to control for gender biases). After a few seconds, they were shown either three negative sentences or three positive sentences, all describing the “face’s” personal character (i.e. “He did a mean thing” or “He helped a little old lady cross the street”). After a few-second interval, they were given the other three sentences (positive if the first three were negative, or vice versa). At the end, the subjects were asked to rate their impression of the face on a scale of 1 (don’t like) to 8 (really like).
(Oh, by the by, please keep in mind that throughout this whole procedure, the researchers were imaging the subjects’ brains with the MRI.)
So after all the evaluations were done, the researchers went on to correlate brain activity with individual impressions of the face. (This, as it were, is the point of any MRI study.) If the subject gave the face a positive score, then the team looked at the brain activity during the presentation of the positive sentences (the “evaluation-relevant” information). Conversely, if the subject said they didn’t like the face, the brain activity during the presentation of the negative sentences was used. In both cases, the sentences opposite the subjects’ evaluations were the “evaluation-irrelevant” information.
With these statistical parameters in hand, the team could isolate which areas of the brain were being called upon when the subjects were forming their impression of the face. The difference in brain activity between presentation of the evaluation-relevant and evaluation-irrelevant sentences should theoretically isolate which areas are specifically utilized to, well, evaluate!
And so it was. Two areas in particular–the amygdala and the posterior cingulate cortex (PCC)–were more highly activated during presentation of information used to make first impressions than when the irrelevant information was presented. Also interesting is the fact that the strength of the activity was tied to how positive or negative the impression was. The stronger the impression (in either direction), the more active the amygdala/PCC.
The amygdala and PCC aren’t the only areas used to form impressions, but they’re undoubtedly important, and they’ve been shown to play critical roles in the general areas of learning, emotion, and arousal (as in motivation, not sexy stuff). A study like this one is instructive, but it’s not going to lay out exactly how impressions are formed on a neural-circuit-based level. There’s no A-to-B here, but rather an A-affects-B-to-a-certain-extent. But being able to point to two areas and say: “These are critical” is neveretheless pretty astounding.