The Length of a Microexpression

What exactly are microexpressions?

While we certainly know how important microexpressions are in reading other people, there are still a great deal of outstanding questions. One of these concerns the very nature of a microexpression: how long do they last? This is an important question in better understanding to what extent they are categorically different from normal expressions.

This was exactly what Dr. Xunbing Shen and his team sought to determine in a 2016 study. They suspected that the process of recognizing a short (less than 200 milliseconds) and a long (greater than 200 milliseconds) expression were distinctive neurological processes. Therefore, they hypothesized that this distinction was also what could distinguish microexpressions from normal, macroexpressions.

Importantly, the researchers employed an “affective priming paradigm,” which utilized a picture of a facial expression to prime an associated emotional word. This attempts to elicit distinctive brain responses when there is a mismatch between word and expression, in this case seeking to hold a microscope up to differing reactions to micro and macroexpressions.

In order to answer their hypothesis, Dr. Shen’s team compiled a small team of volunteers. These participants were shown a series of images showcasing 30 different expressions, displaying either fear, happiness, or a neutral expression, alongside a related series of 100 emotionally significant words.

The series of faces were paired with words, some of which matching the emotion expressed and some of which not. Moreover, the exposure to faces was varied from 40 to 300 milliseconds, in order to test the impact of fleeting microexpressions. During this process, brain scans recorded activity that occurred as participants attempted to identify the emotions expressed.

After completing the experiment, Dr. Shen and his team compared brain activity during both long and short duration expressions. They found significant differences, with the brain’s left hemisphere more active while perceiving microexpressions, for example.

While these results may seem strange, given that expressions are the same regardless of the duration. The study concludes by offering some possible explanations. Essentially, it takes more attention to perceive a shorter expression. This may be because mimicry is crucial to detecting expressions, and this is hard to do quickly. Instead, participants were forced to tap into their memory in hopes of identifying the expression that way.

There are certainly still some unanswered questions, but this work helps further distinguish the process of expression recognition. It is not just a matter of recognizing fleeting variants of normal expressions, as microexpression recognition is a wholly distinctive neurological process.

Naturally, Humintell is pretty excited at the multitude of directions that exist to study microexpressions. If you share this enthusiasm, check out some more information or consider enrolling in a relevant training class!

One response to “The Length of a Microexpression”

  1. Julien Michaliszyn says:

    Very interesting.

    However, it seems to me that this study is more about the nature of the processing of micro vs macro expression by the brain that about the nature of these expressions and their production. The study illustrate well the dichotomy between preception and production : in the study, the nature of the stimuli is the same (a picture of an emotional expression on a screen) and the only thing that differs is the length of exposition. But the brain react differently to different length for stimuli of “same nature”.

    This lead me to a question, that I had ask you before. Your answer was a link to some articles of this blog. Unfortunately, these articles doesn’t answer this specific question, so I take the liberty to ask you again :

    H1 :Does macro and micro-expression are really two distinct category of facial expressions with a “gap” of length between them (the micro with a lenth of 1/25 of s, Nothing between and at 1 secondand more we have macro-expression) ?
    H2 : Or it is a continuum (with some expressions that are a bit longer than a micro but not to the extent that we can consider them as a macro-expression either) ?
    If H1 is exact, do you have hypothesis about why there is a gap with no expression with in-between length are produced ?
    If H2 is exact, why the length of 1/25 of a second is the threshold ?

    Thank you for your attention, of to continue this blog that is really interesting ad informative.

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