A blink takes about 300 milliseconds. The time it takes to read this sentence? Several seconds. The time it takes someone to decide whether you're trustworthy, competent, and likeable? One hundred milliseconds. Less than half a blink.
This isn't a metaphor or an exaggeration. It's a research finding that should fundamentally change how you think about first impressions. By the time your audience becomes consciously aware of you, they've already made up their minds.
The Research
In 2006, Princeton psychologists Janine Willis and Alexander Todorov published a study that quantified something most of us suspected but couldn't prove: first impressions form almost instantaneously.
They ran five experiments with approximately 200 total participants. The methodology was elegantly simple. Participants viewed faces of unfamiliar people for varying lengths of time: 100 milliseconds, 500 milliseconds, 1000 milliseconds, or with unlimited time to study the face. After each exposure, they rated the faces on key traits including trustworthiness, competence, likeability, aggressiveness, and attractiveness.
The findings were remarkable. Judgments made after just 100 milliseconds of exposure correlated highly with judgments made when participants had unlimited time. A tenth of a second was enough to form opinions that matched what careful, deliberate evaluation would produce.
Of all the traits measured, trustworthiness was judged fastest. This makes evolutionary sense. Knowing whether someone poses a threat requires an immediate answer. You can take your time assessing competence. You cannot take your time assessing danger.
Why This Happens
The speed of these judgments isn't a flaw in human cognition. It's a feature. Our ancestors who waited to carefully evaluate whether an approaching stranger was friend or foe often didn't survive long enough to have descendants. The humans who made it this far are the ones whose brains were wired for rapid threat assessment.
What's remarkable is how this ancient survival mechanism operates today. Your brain makes complex social evaluations in the same time it takes to process basic visual information. These aren't snap judgments that get revised with more data. The Willis and Todorov research showed that additional time beyond 100 milliseconds only increased participants' confidence in their judgments. It didn't change what those judgments were. People didn't become more accurate with more time. They just became more certain they were right.
This has profound implications for anyone who speaks, presents, or interviews. The moment you step into a room or begin speaking, the evaluation is already underway. And it's not a preliminary assessment that gets refined. It's a first impression that additional information tends to confirm rather than revise.
Practical Applications
Knowing that 100 milliseconds determines so much, what can you actually do about it?
1. Master Your Opening Energy
Most speakers obsess over their first sentence. The research suggests your tone and presence have already communicated something before your first word lands. Start with the energy you want to project. Let your voice convey warmth and confidence from the very first syllable. These signals register before conscious processing kicks in.
2. Prepare Your Presence, Not Just Your Content
Rehearsing what you'll say is valuable. Rehearsing how you'll sound in those first moments is equally important. Record yourself starting a presentation. Notice your tone, your pace, your energy in that initial second. That's what your audience is evaluating while you're still saying hello.
3. Warm Up Before You Speak
Your first words in any situation carry disproportionate weight. If you're about to interview, give a presentation, or join an important meeting, do a vocal warmup first. A few minutes of speaking aloud, even to yourself, ensures your voice is ready to project confidence when it matters most.
4. Accept the Information Asymmetry
You cannot force someone to find you trustworthy or competent. You can only present yourself authentically and let their rapid evaluation process do its work. Trying to manipulate these instant impressions tends to backfire. People are remarkably good at detecting inauthenticity, even in a fraction of a second.
The Bottom Line
One hundred milliseconds is less time than you can consciously perceive. Yet in that microscopic window, your audience forms judgments about trustworthiness, competence, and likeability that additional time merely reinforces. This isn't something to fear. It's something to accept and prepare for. The evaluation begins the instant you start speaking. Make those milliseconds count by being genuinely present, energized, and ready before the moment arrives.
Put This Into Practice
While this research focuses on visual first impressions, the same principle applies to how you sound. People judge your voice just as quickly: confidence, competence, and warmth all come through in your first few words.
Impromptu practice in speaking.app lets you record yourself responding to unexpected questions, so you can hear how you come across in those critical first moments. Interview practice helps you nail your greeting and "tell me about yourself" response. You'll get AI feedback on filler words, pacing, and structure, helping you sound confident and prepared before the real stakes arrive.
Practice your presence, not just your words.