Just like falling in love, we can form friendships at first sight

Call it a spark, call it chemistry, call it friendship at first sight; whatever it is, it can happen in just a small handful of seconds, which is the amount of time we need to form a first impression of someone (if that — one study suggests that we make our judgments just a tenth of a second after seeing a face). In a study published in Nature in 2009, researchers identified two areas of the brain that become especially active when we meet someone new: the amygdala, the area of the brain that deals with emotion, and the posterior cingulate cortex, which is linked to autobiographical memory. As Karla Starr noted in Psychology Today, the posterior cingulate cortex also helps us weigh decisions and assign value to objects; we go through a very similar process with humans. “And after we’ve assigned a value to a person, we make the decision about how to orient ourselves to that person,” she wrote. “Do we want to get closer? Knowing what this person’s value is to us, do we want this person to be involved in our network?”

The answer is actually a compilation of several smaller judgments, explains Kelly Campbell, a psychology professor at California State University, San Bernardino. “What are the things we care about in a friend? We care about someone who’s going to be fun, that we can enjoy ourselves with … You need emotional support, social support, you want then to be loyal and trustworthy, you don’t want to feel judged,” she says. “When you first see the person, you don’t realize how many judgments you’re making, but you’re actually gathering information that’s telling you if this person fills those needs for you.”