The invitation says cocktails at 6:30. You’re already fashionably late because you’re waiting for your nails and shimmer body lotion to dry. As you lean into the mirror to do your mascara, you review the possibilities.

Will you meet a new man or will the evening be romantically uneventful? Eyes done, you move on to your lips. a new tube of crimson-red lipstick gives you a shot of confidence before you slip on the pièce de résistance: your little black party dress.

It too you two hours to get ready, but within seconds of making your party entrance, other guests will already have a first impression of you. “At five seconds, we can be fairly accurate about how attractive and extroverted a person is, but if we want to know how conscientious or neurotic the person might be, we need more time — at least a minute or more,” explains Randy Colvin, associate professor of psychology at Northeastern University in Boston.

“Strangers only see a sample of you in that time, a tiny percentage of your life,” add Anne Demarais and Valerie White, authours of First Impressions: What You Don’t Know About How Others See You, “but they unconsciously assume that small sample is an accurate representation of all of you.” Sure, it may be unfair, but that’s how human interactions work.

Photo courtesy of Le ChateauAccording to Nalini Ambady, professor of psychology at Tufts University in Medford, Mass., we form certain types of impressions or “thin slices of experience” in a primitive area of the brain where feelings are processed. This accounts for the emotional response — both negative and positive — we can have when we first meet someone. “We probably have it hard-wired into our system, to figure out certain types of relationships,” she explains. “Is this person going to be a foe or a friend? Are they dominant or aggressive?”

So how reliable are these first impressions? A lot depends upon the person we’re sizing up, says Colvin. People who are mentally healthy are the easiest to judge because their body language is a direct reflection of their internal views of themselves. In other words, what you see is what you get. Emotionally stable or not, we can all be fooled by physical features. For example, we tend to view people with a “baby face” (round cheeks, large eyes, a small nose and chin) as non-threatening and more trustworthy. On the flip side, if someone has large ears, we may think they’re dumbos with a lowe IQ, says Colvin.

In the end, while good grooming, the right wardrobe and the right body language all matter, the trick to making a good first impression, says Demarais, is really about being socially generous. “It’s about putting aside your own needs, focusing on making the other person feel good and knowing that eventually it will come back to you.”

Photo courtesy of Le Chateau