How Fast are the Leaked Facial Expressions: The Duration of Micro-Expressions

Micro-expression has gained a lot of attention because of its potential applications (e.g., transportation security) and theoretical implications (e.g., expression of emotions). However, the duration of micro-expression, which is considered as the most important characteristic, has not been firmly established. The present study provides evidence to define the duration of micro-expression by collecting and analyzing the fast facial expressions which are the leakage of genuine emotions. Participants were asked to neutralize their faces while watching emotional video episodes. Among the more than 1,000 elicited facial expressions, 109 leaked fast expressions (less than 500 ms) were selected and analyzed. The distribution curves of total duration and onset duration for the micro-expressions were presented. Based on the distribution and estimation, it seems suitable to define micro-expression by its total duration less than 500 ms or its onset duration less than 260 ms. These findings may facilitate further studies of micro-expressions in the future.