Discover the neuroscience of smiling and first impressions. Research shows people judge you in just 100 milliseconds—learn how to make those milliseconds count.
Written by Laura Bouttell • Sat 24th January 2026
Here's a number that should change how you think about meeting people: 100 milliseconds.
That's one tenth of a second. That's how long it takes for someone to form their first impression of you.
Princeton psychologists Janine Willis and Alexander Todorov conducted a series of experiments showing participants photographs of faces for varying durations: 100 milliseconds, 500 milliseconds, and 1,000 milliseconds. They found that impressions formed in just 100 milliseconds didn't significantly change with longer exposure. More time increased confidence in the judgement, but the judgement itself was already made.
Another study from the University of York suggested that a single glance of 33 to 100 milliseconds is enough to form a first impression. Thirty-three milliseconds. The blink of an eye takes longer.
This isn't about conscious evaluation. It's not someone carefully weighing your qualities. It's your brain's ancient threat-detection system firing before you've had a chance to say hello.
The fastest judgements? Attractiveness and trustworthiness. Before you've opened your mouth, people have already decided whether they find you trustworthy.
Knowing that impressions form instantly, what can you control? You can't change your bone structure in the reception area. You can't redo your haircut between shaking hands.
But you can smile.
And here's what's remarkable about smiling: it changes you as much as it changes how others perceive you.
When you smile, your brain releases neuropeptides that reduce stress. Neurotransmitters like dopamine, endorphins, and serotonin flood your system. This isn't metaphorical—it's measurable neurochemistry.
Even forcing a smile during stress reduces the intensity of your body's stress response. The physical act of smiling triggers the emotional state associated with genuine happiness. Your body works backwards, using the expression to generate the feeling.
So when you walk into a room smiling, you're not just looking more approachable—you're actually becoming calmer, more confident, more present. The smile works on you while it works on them.
Smiles spread.
Mirror neurons in the human brain fire when we observe expressions in others, causing us to automatically mimic them. When you smile at someone, they almost always smile back. It's not a choice—it's neural architecture.
This means your smile creates a cascade. You smile, they smile, their mood lifts, they treat the next person better. One genuine smile can ripple through an entire office.
Think about the people you most enjoy being around. Chances are they smile easily. They bring positive energy into rooms. Being around them feels good. That's not personality—that's contagion. And it's learnable.
Of course, not all smiles are equal.
A forced smile—what psychologists call a "non-Duchenne smile"—involves only the mouth. The lips curve upward, but the eyes stay unchanged. We can spot these almost instantly, even if we can't articulate what's wrong.
A genuine smile—a "Duchenne smile"—engages the orbicularis oculi muscles around the eyes. The eyes crinkle, the cheeks lift. It's involuntary, which is why it's hard to fake.
People know the difference, even unconsciously. A fake smile triggers suspicion. A genuine smile triggers trust.
So how do you generate a genuine smile on command? You don't fake the expression—you create the feeling.
Before walking into a meeting, take five seconds to think of something that makes you happy. A loved one. A favourite memory. An accomplishment you're proud of. A joke that still makes you laugh.
Your face will respond naturally. Now you're not manufacturing an expression—you're experiencing an emotion that happens to show on your face.
Build a habit. Every time you're about to meet someone new, trigger your genuine smile:
After a few weeks, the ritual becomes automatic. Your brain associates "about to meet someone" with the positive feeling, and the smile comes without conscious effort.
Don't reserve your smiles for important people. Smile at the receptionist, the security guard, the person in the lift. Each interaction is practice. Each positive response reinforces the habit.
And you never know who matters. The person you dismissed in the lobby might be the CEO's spouse. More importantly, they're a human being who deserves your courtesy.
Here's something that surprises people: your smile affects your voice even when the other person can't see you.
When you answer the phone with a smile, your voice changes. The tone lifts. The warmth comes through. Telephone operators trained to smile during calls consistently report better customer interactions.
Try this experiment: record yourself saying "Hello, how can I help you?" with a frown, then with a genuine smile. Play back the recordings. The difference is unmistakable.
Your body is integrated. What shows on your face shows in your voice.
The most valuable smile is one that persists regardless of external conditions.
Anyone can smile when things are going well. The client just signed. The presentation went perfectly. You got the promotion.
But the person who can maintain underlying warmth during difficulty—who doesn't let temporary setbacks drain their positive energy—stands out.
This doesn't mean suppressing genuine emotions or pretending everything is fine when it isn't. It means not letting your default state become negative. It means choosing, moment by moment, to approach the world with openness rather than defensiveness.
As the old Chinese proverb says: "A man without a smiling face must not open a shop."
William B. Steinhardt, a New York stockbroker, had been married for eighteen years. In all that time, he rarely smiled at his wife from the moment he left for work until he sat down to dinner.
When challenged to try smiling for just one week, he decided to start that very morning. He looked in the mirror and said to himself: "Bill, you're going to wipe that scowl off your face today. You're going to smile."
At breakfast, he greeted his wife with "Good morning, my dear" and a smile.
She was stunned. She asked if he was all right.
He kept it up. "This has been the happiest day of our married life," his wife later told him.
Steinhardt continued the practice. Two months later, he reported: "There is more happiness in my home than ever before. When I leave for work I smile at the doorman and say good morning. I find that smiles are bringing me dollars—many dollars every day."
The man hadn't changed his circumstances. He'd changed his expression. And his entire life transformed.
Consider what a smile gives you:
Consider what not smiling costs you:
The maths is overwhelming. And yet most people walk around with their default expression somewhere between "mildly concerned" and "vaguely annoyed."
A smile opens the door. It creates the initial warmth that makes someone willing to engage with you.
But it's just the beginning. Once you've created that initial connection, the next step is to remember and use people's names—the sweetest sound in any language.
Then you show genuine interest through listening and talking about their interests.
Your smile gets you in the door. These other skills keep it open.
On our Quarterdeck courses, we suggest a simple daily practice.
Every morning, as you're getting ready:
This isn't positive affirmation nonsense. It's training your face to remember what smiling feels like, so you can access that expression more easily throughout the day.
Do it for a week. Notice what changes.
Principle 2: Smile.