Walking alone through a parking garage you see a figure lurking by your car. An unsettling feeling in the pit of your stomach alerts you to turn and walk the other way. Before that person can prove their intent, intelligence or charisma, you have already formed an impression. Instinct is nature’s surest defense mechanism, and it’s deeply rooted in our anatomy.

But what goes through the mind when seeing a face? When cavemen saw an unfamiliar person, they didn’t have the brain power to ask about purpose. All they had were visual cues. Today, judging someone’s intentions is a little more complex, but appearance still has everything to do with a first impression.

“You want to get some sort of immediate physical indicator of the person’s intentions, whether it’s going to be helpful or harmful,” says Dr. Alan Swinkels, psychology professor at St. Edward’s University.
This same idea inspired a study by two psychologists who wanted to know more about mixed signals during first impressions. Princeton psychologist Alexander Todorov and NYU psychologist James Uleman created a program that helps determine what facial features people do and don’t trust.

University students were simply exposed to a series of different computer-generated faces.
Each face was randomly matched with one of the seven basic human emotions: anger, sadness, fear, surprise, disgust, contempt and happiness. Nearly every time, participants linked the same traits to the same faces.

“From an evolutionary standpoint, it makes a lot more sense to do a quick sizing-them-up based on facial appearance alone,” says Swinkels. “That’s what is going to be more adaptive, because people are going to stay alive longer, be able to procreate and make a new generation.”

A topic Swinkels focuses on in social psychology is automatic versus controlled processing. Controlled is very deliberate, because all the evidence comes from being rational and taking things step-by-step. Automatic processing instantly gives all the information needed to make a judgment.

“It turns out that humans are pretty good with automatic judgments,” he says. “It’s also turning out that a lot of social life is at this automatic level. When somebody walks by, you think you know everything you need to know about that person. Almost everybody works that way.”

More research by Todorov exposes a tiny, almond-shaped part of the brain called the amygdala, which is primary for emotional reactions. According to Swinkels, there is an entire constellation of cells that process facial features and expressions; although each individual cell may play a different role. When someone sees a face they think is threatening, the amygdala alerts their nervous system. Reasoning comes from the cortex, a frontal development of the brain.

What about a non-threatening face? Someone with “baby-face” qualities, such as big eyes, small chin and round cheeks, was tested as the most trustworthy. Even if the person is a grown adult, they are still associated with child-like characteristics. A good example, Swinkels says, is a construction worker with a boyish face. No matter how much weight he is carrying over his shoulder, your brain registers how youthful he looks. This is your automatic judgment kicking in.
“They’re seen as more naïve and needing of help,” Swinkels says. “Defendants who have baby faces are often given more lenient sentences — precisely because they are seen as less culpable and more innocent.”

Todorov says his research parallels some issues in “Blink,” a book by New York journalist Malcolm Gladwell about the rapid cognition in our minds when making decisions in the “blink” of an eye. Gladwell’s inspiration for the book was the quick judgments people made about him because of his long hair. A social status, like hair length or facial hair, is associated with specific social classes through automatic judgment.

“This paper’s results concern specific mechanisms in the mind, while ‘Blink’ makes broader generalizations,” Todorov said. “Gladwell’s basic message is not essentially different from ours, though he views snap judgments to be primarily rational in nature. Our research finds that this is often the case, but not always.”

All this may or may not be surprising, but it all points back to instinct and intuition. Looks are only half of the final judgment. It also has to do with actions and true intentions. Todorov reiterated that quick first impressions cannot be overcome by the rational mind. Being able to reason and make an educated decision is how we evolve. If judgment was based strictly on instinct, you wouldn’t get much farther than believing what someone looks like must be who they are.

“Instinct is kind of a loaded word,” Swinkels says. “You don’t have to necessarily look at the baby-faced guy and think he is innocent. Whatever you want to call it — instinct, tuition or survival instinct — people have that in the terms of getting immediate information.”