How much time do you need to spend with a person before you’re able to make an accurate judgment of their character? How quickly can you decide if the person is an expert? It turns out you don’t need much time at all. In many instances, our first impressions are more than enough.

In 1993 researchers videotaped several college instructors while they were teaching. Then they extracted sections of the instructors’ presentations—segments of two, five, and, ten seconds long—which they called thin slices. The researchers showed the segments to strangers and asked them to rate each teacher’s effectiveness. They compared the strangers’ assessments with the traditional teacher assessments given by students at the end of a semester of instruction. Remarkably, the strangers’ appraisals of the instructors after just a few seconds of silent video were highly correlated with student assessments after months of interaction.

“Thin slicing,” as the phenomenon was dubbed, refers to our ability to view narrow slivers or samples of situations without losing meaning. Th in slicing has been validated and revalidated many times across many disciplines. It applies to job interviews, dating, sales, doctor/patient relations, and more. Out of necessity, people are slicing subject matter experts more and more thinly and passing judgment more and more quickly. As an SME, you are being thinly sliced.