What can a vine — a five- to 10-second-long video clip — teach you about social intelligence (or people smarts)? Lots, apparently. Long before viral vines came along, social psychologists Nalini Ambady and Robert Rosenthal used them to demonstrate that students could accurately predict the best teachers in a group, even when judging the unfamiliar teachers based on six-second-long silent videotapes. From this work, the psychologists coined the term thin slice to refer to how brief a sample experience is needed for one person to accurately judge another.

In the experiment, the researchers videotaped 13 graduate teaching fellows as they instructed a class. Next, the researchers removed three 10-second clips and spliced them together into one 30-second silent tape for each teacher. Then, the partners showed the clips to new students and tasked them with judging the teachers based on specific traits, including perceived competence, professionalism, enthusiasm, and empathy. After combining individual scores into an overall rating for each, the research team compared these ratings to the teachers’ end-of-semester evaluations from students actually taking their classes.

What did the researchers discover?

The match between evaluations was high — the video-watching students had ranked the unfamiliar teachers more or less the same as students who had actually taken classes with them.

But here’s the kicker: The researchers cut each teacher’s silent videotape down to 15 seconds and then again down to the length of a vine — six silent seconds long. Again they ran the experiment with a new set of students, and once again, they accurately predicted the most successful teachers… after watching them for just six seconds. It turns out that such thin slices — occurring in less than two seconds (the blink of an eye) — are not only accurate, they are also the basis for many of our opinions and decisions.

Thin Slices in Action

Exploring thin slices in detail, Malcolm Gladwell wrote a book, Blink, examining the wheres and whys of snap judgments. He explained his reasons for writing the book in an interview. One day, he decided to grow out his hair after wearing it conservatively short for some years. After his curly hair had blossomed, he found himself on the receiving end of no small amount of negative attention, including getting stopped for speeding tickets and once being questioned by New York City cops searching for a rapist. What struck him most was the fact that the stereotyping wasn’t about something more obvious, in his words, like skin color or age. “Something about the first impression created by my hair derailed every other consideration in the hunt for the rapist, and the impression formed in those first two seconds exerted a powerful hold over the officers’ thinking over the next twenty minutes,” he stated in an interview. “That episode on the street got me thinking about the weird power of first impressions.”

Importantly, then, it was an instant judgment gone wrong that led Gladwell to write a book about the opposite occurrence: just how often such thin slices lead to correct decisions. He also narrates how a public hospital in Chicago instructed doctors to collect less information from patients experiencing chest pain and encouraged them to be mindful of crucial data, such as blood pressure, while ignoring age and weight and medical history. The result was a radical uptick in correctly diagnosing heart attacks.

In many situations, according to Gladwell, we are making judgments in less than two seconds and though that may seem far from ideal, it really isn’t a bad thing. “There are lots of situations — particularly at times of high pressure and stress — when… our snap judgments and first impressions offer a much better means of making sense of the world,” he said in an interview. Effectively, we can think without thinking in the briefest snatch of time, and in many situations, it is actually best not to over-think the issue, as your friend might say.

We all know, though, that snap judgments are not always accurate or helpful. Gladwell’s long hair, for instance, misled some to judge him incorrectly. Consider, too, the many women who say they didn’t really like, at least at first, the guy they end up marrying. (Seems like fewer guys ever say that!) Awareness, then, is key. Once you understand this ability (and tendency) to judge in the blink of an eye, the choice is yours to ponder some decisions in some cases… and to act on instinct in others.