The Science of First Impressions

| Fremont, California

A man holding a thumbs down icon and a woman holding a thumbs up icon communicate via speech bubbles, representing opposing impressions.

Have you ever come across someone and immediately gotten an unexpected feeling or comfort, or felt a distinct wave of unease where there’s just something likeable or inherently untrustworthy about them? This could be the newly enrolled student entering the classroom, an interviewer welcoming you in a simple manner, or even a person whose profile you see on your social media Instagram or Tiktok feed. It is a universal human experience to size up a stranger instantly; without conscious thought, everyone subconsciously makes judgements about the people they encounter.You would be surprised to learn that even before they greet you or utter a greeting like “nice to meet you,” chances are that you’ve already formed an impression on them. Despite us being taught the saying, "Don't judge a book by its cover," our brain doesn’t get the message.

Studies show that people tend to form impressions of others in as short as a tenth of a second. In a 2006 study published in Psychological Science by Princeton researchers Janine Wills and Alexander Todorov, participants were exposed to faces for 100 milliseconds, 500 milliseconds, or 1,000 milliseconds. The researchers found that increases in exposure time did not significantly alter the initial judgements; rather the split second window was enough for the brain to lock in its assessment. Our brains make assumptions regarding whether someone looks warm, competent, trustworthy or approachable within that short amount of time. It may seem unjust, but there is a clear scientific explanation why our brains act like a rapid fire personality “Judge Judy”.

A few millions of years ago, long before the invention of fire and early civilizations, our early ancestors had no time to talk and spend hours learning about the strangers they came across in their journey. They had to make quick judgments based on how dangerous or friendly the people around them were. Such assessments helped them to survive in their habitats. However, in the modern era, the question "Is there a potential threat for me in this person?" does not come to mind anymore, but our brain continues to use the same neural shortcuts. In other words, instead of thinking if one could be threatened by someone we come across, we wonder if we would like to work for this person or if that individual could be a future companion, friend, or work buddy.

It is worth noting that the brain does not always help us to draw correct conclusions. For instance, there is such a psychological phenomenon known as the halo effect. When one is coming across someone who dresses up nicely, looks self-confident, and talks eloquently, we may unconsciously consider him or her an intelligent, diligent, and good-natured person. On the contrary, if someone appears shy and nervous, we consider that person as unfriendly or underprepared. In reality, the confident person could be having the worst day of their life, and their counterpart simply needs a few minutes to catch their breath and regain their composure. This aspect of cognitive bias severely damages people’s perceptions and ruins others’ reputations, as it constructs a wall of perfection or flaw based on superficial traits, causing us to overlook flaws or hidden talents.

What is really amazing about these initial moments when you meet someone is that the words used are not always the most important things that go into first impressions. Before any conscious processing starts regarding another person’s statement, the manner in which they say something has the spotlight. A natural smile, posture, eye contact, and even tone of voice are all cues that are picked up almost automatically by our brain. We sort of read an unspoken language without noticing it.

The real challenge comes from the fact that once we form an impression, we get quite adept at defending it. For example, if we feel they are humorous, we will note every single joke or jesting antics they ever tell. On the other hand, if we believe they are being rude, we will spot everything they do that justifies that belief. This is referred to as confirmation bias, and it is one of the reasons why first impressions tend to last so long despite being untrustworthy.

Think about the last time when you have been startled by something. Perhaps your classmate who appeared scary turned out to be a source of endless laughs. Alternatively, maybe an individual you saw as a silent person ended up becoming one of your best friends. In both cases, had you relied on your first impressions only, you wouldn't get to know him or her properly. It seems that first impressions tend to be a very quick, strong, and incomplete manner of categorizing strangers

Are your parents right that first impressions are vitally important? Yes, without doubt, they may affect our relationships, career, and the way other people will remember us. However, first impressions  seem to prove that we like our brains to use shortcuts and take them literally. Next time you find yourself judging somebody based on the very first interaction that lasted for a matter of seconds, remind yourself that your brain does what it has evolved to do, but this doesn't necessarily mean that it knows better.

Works Cited

Casad, Bettina J., and Stephen Eldridge. “Confirmation bias | Definition, Examples, Psychology, & Facts.” Britannica, 11 June 2026, https://www.britannica.com/science/confirmation-bias. 

“First impressions: making up your mind after a 100-ms exposure to a face.” PubMed, https://pubmed.ncbi.nlm.nih.gov/16866745/. 

“Heuristics: Definition, Examples, and How They Work.” Verywell Mind, 4 June 2026, https://www.verywellmind.com/what-is-a-heuristic-2795235. 

Laski, Benjamin. “The Power of First Impressions.” Florida Atlantic University, 17 April 2025, https://www.fau.edu/thrive/students/thrive-thursdays/thepoweroffirstimpressions/. 

Neugaard, Britta, and Naomi Ellemers. “Halo effect | Attribution, Perception, Bias.” Britannica, 26 June 2026, https://www.britannica.com/science/halo-effect.