How the Brain Forms First Impressions

Melissa Hughes
May 1
3 min read

You know the feeling.

You meet someone and immediately get that gut reaction—something’s off.

You don’t trust them.

You don’t like them.

You don’t know why.

Spoiler alert: It’s not just intuition.It’s neuroscience.

With every new encounter, you form an immediate impression and another person's immediate impression of you is formed. These first impressions are powerful forces in setting the tone for that single exchange or the quality of the relationship you may have with him or her going forward.

In a fraction of a second, you determine a level or like or dislike about someone you’ve never met. In fact, studies have demonstrated that it only takes 100 milliseconds to form a first impression about a stranger. To put that into perspective, it takes about four times longer to blink.

In less than a tenth of a second, your amazing brain is able to piece together information from emotional memories, past experiences and personal values to form a judgement about that person. In the next few seconds, you have a bias about that person - either positive or negative.

Your brain is constantly taking mental shortcuts called heuristics. They're efficient, but not always accurate. We “thin slice”—using just a sliver of information to make broad assumptions.We also rely on confirmation bias—the tendency to notice things that support our initial impression and ignore the rest.

So if someone seemed standoffish in the first few seconds, our brains go hunting for more reasons to justify that opinion. It’s not just about faces, either. Tone of voice, posture, clothing, eye contact, and even microexpressions all get processed and interpreted—lightning fast.

Oddly enough, giving someone additional time doesn’t improve the judgements made. According to research, when exposure time increased from 100 to 500 milliseconds, people felt more confident in their initial impressions rather than alter the judgements based upon any additional information they may be able to collect about them.

Physical characteristics such as piercings, hair color, tattoos, and clothing all influence that fraction of a second judgement about someone. People who smile are perceived to be more attractive. Attractiveness aside, our first impressions are largely distilled down to friend-or-foe and powerful-or-no. Impressions of trustworthiness and power form the basis of the structure of impressions. In other words, it’s all about our perception of someone’s intentions towards us.

Researchers are now using computer-generated morphed and synthetic faces to explore this further. Alexander Todorov, a psychology professor at Princeton University, is leading the way in this field. He discovered that candidates in an election who were judged to look more competent than their rivals by naive voters were also more likely to have won.

Other studies have found that 7-month-old babies make the same judgements about trustworthiness as adults, and that simply increasing or decreasing skin brightness can radically alter impressions. Brighter faces appear more trustworthy, submissive and feminine. Changing the “reflectance” without altering anything else can change a male-looking face into a female-looking face, and the reverse is also true.

Other studies have also suggested that media can largely affect how we form first impressions. People who reported frequent media multitasking are more likely to be distracted by irrelevant information when making first impressions about someone they had never met, compared with those who did not engage in frequent media multitasking. Multitasking with media had a direct correlation with character judgements based on physical attributes.

The Cost of a Bad First Impression

Here’s the kicker: once that negative impression is made, it’s hard to undo.Studies show that even when presented with new, positive information, people often stick with their initial gut feeling. That’s because the brain prefers consistency over correction. It takes more cognitive effort to revise an opinion than to maintain one.

Whether you’re in hospitality, leadership, sales, or just meeting someone new—you are either winning or losing in those first moments.

This isn’t about being fake. It’s about being aware. When we understand the brain’s default settings, we can: