Within seconds of meeting someone, you've already decided whether you like them. You've assessed their competence, trustworthiness, and likability based on almost no information—their face, their handshake, a few words. This judgment feels like knowledge, but it's mostly pattern-matching happening below conscious awareness.

First impressions are remarkably sticky. Even when subsequent information contradicts them, the initial judgment influences how we interpret everything that follows. Someone who seemed unfriendly at first must "really" be cold, even when they act warmly later. The first impression becomes a lens that distorts all future perception.

Why are we so quick to judge, and why do those quick judgments persist so stubbornly?

The Problem This Was Meant to Solve

In ancestral environments, encounters with strangers were potentially dangerous. A person approaching your group might be a friend or a threat. You had to decide quickly whether to fight, flee, or welcome them. Taking too long to deliberate could be fatal. Speed of judgment was literally a survival skill.

First impressions evolved as rapid threat assessment. The brain processes visible cues—facial expression, body posture, physical size, group affiliation—and generates an immediate evaluation. This evaluation triggers appropriate responses before conscious thought has time to engage. You react to danger before you "decide" to react.

Beyond threat assessment, first impressions helped navigate social complexity. Tribal societies required tracking many relationships with nuanced dynamics. You couldn't spend unlimited time evaluating every person; you needed shortcuts. First impressions provided quick initial categorizations that could be refined later if the relationship warranted investment.

The stickiness of first impressions also served purposes. Updating beliefs requires cognitive effort. If every new piece of information required complete reevaluation, you'd be paralyzed by processing. Anchoring on first impressions and only adjusting when compelling evidence arrived was more efficient. The system was designed for good-enough judgment, not perfect accuracy.

How It Actually Came to Exist

Research on first impressions began in earnest in the 1940s with psychologist Solomon Asch, who demonstrated that initial information disproportionately shapes overall impressions. In his famous experiments, describing someone as "intelligent, industrious, impulsive, critical, stubborn, envious" created a different impression than the same words in reverse order. What comes first colors everything after.

Neuroscience has identified the amygdala as central to rapid social judgment. This primitive brain structure processes faces extremely quickly—before conscious recognition—and generates emotional responses. The feeling of trust or distrust you experience upon meeting someone often begins in the amygdala's millisecond-fast processing.

The specific dimensions of first impressions have been mapped. Research by Princeton psychologist Alexander Todorov found that faces are primarily judged on warmth (is this person a friend or foe?) and competence (can this person act on their intentions?). These two dimensions capture most of the variation in first impressions and may reflect the most survival-relevant information about others.

Studies have shown that first impressions form in as little as 100 milliseconds—a tenth of a second. Longer exposure increases confidence but doesn't necessarily change the judgment. We decide almost instantly and then become increasingly certain we're right, even without additional information to justify that certainty.

Why It Still Exists Today

First impressions remain psychologically powerful because the underlying cognitive systems haven't changed. We still have amygdalae that process faces quickly. We still make rapid assessments of warmth and competence. Evolution moves too slowly to have rewired these systems for modern environments.

Modern life actually increases reliance on first impressions. We encounter more strangers than our ancestors did—at work, in cities, online. We can't develop deep knowledge of everyone we meet. Quick categorization is more necessary, not less, when the number of people we encounter is so large.

Digital environments have amplified first impressions in new ways. Dating apps require judgments based on photos and brief profiles. LinkedIn creates impressions from headshots and job titles. Social media profiles are exercises in first impression management. The snap judgment that evolved for in-person encounters now operates on digital representations.

Professional contexts have formalized first impressions into institutions. Job interviews, in which candidates are judged quickly on limited information, are essentially structured first impression exercises. Research consistently shows that interviewers form judgments in the first minutes and spend remaining time confirming them.

What People Misunderstand About It

The biggest misconception is that first impressions are accurate. While they do capture some real information—there's modest correlation between first impressions and actual traits—they're also riddled with biases. Attractive people are judged more positively. People who look like those we already trust get automatic trust. First impressions are quick, not accurate.

Many people don't realize how much first impressions are influenced by factors irrelevant to actual character. Height, voice pitch, facial symmetry, clothing—all shape impressions despite having little to do with competence or trustworthiness. The confidence we feel in our judgments isn't matched by their validity.

Another misconception is that first impressions can be easily overcome with contradictory evidence. In reality, the confirmation bias means we interpret ambiguous information in ways consistent with our initial impression. Someone we initially disliked is "obviously faking" their later friendliness. The first impression becomes self-reinforcing.

Perhaps most importantly, people underestimate how much first impressions affect real outcomes. Hiring decisions, voting choices, legal judgments—all are influenced by snap judgments that should be irrelevant. First impressions exist because rapid assessment had survival value, but their persistence in modern contexts where they're inappropriate creates real injustice.