Drs. David Matsumoto, Humintell’s director, and Hyisung Hwang continue their research into facial expressions of emotion with their latest research on judgments of subtle facial expressions of emotion.

Past Studies:
Previous studies on judgments of facial expressions of emotion have primarily utilized prototypical, high-intensity expressions. These are expressions that involve full-face configurations with contractions of muscles at high-intensity levels with no other muscle innervations.

This study: Subtle Facial Expressions of Emotion
This research examined judgments of subtle facial expressions of emotion, not only low-intensity versions of full-face prototypes, but also variants of those prototypes. It also examined how signal and intensity clarities of the expressions were associated with judgment-agreement levels.

Subtle facial expressions are not a new concept and were originally suggested over 30 years ago in the original version of the Facial Action Coding System Manual (FACS).  FACS is a technique for measuring any facial behavior including but not limited to emotional expressions.  It allows for the identification of each of the functionally independent muscle movements in the face.  There are roughly 40 AUs (action units) that are currently identifiable.

The seven universal facial expressions of emotion all have a listing of the proposed AU configurations for each expression including the proposed variants of each facial expression of emotion. However, there has not been an operational definition for subtle expressions that involve low-intensity and/or few appearance changes in the face.

There are two theories on the existence of subtle expressions:
1.      The first is that they are produced because of learned cultural and/or individual habits that modify the full-face, prototypic configurations.
2.    The second suggests that subtle expressions are produced as the result of a cumulative series of sequential checks in the appraisal process that can produce a wide variety of expressive configurations.

It is important to note that this study’s purpose was not to examine which theory is more accurate on the underlying reasons subtle expressions exist, but to identify which subtle expressions may have signal value as emotions.

The Study’s Findings:  Examination of variant expression obtained significantly greater-than-chance percentage-agreement rates of the intended emotion suggested potentially new facial configurations of subtle emotional expressions.

Low-intensity, full-face prototypical expressions of emotion were judged as the intended emotions at rates significantly greater than chance. A number of the proposed FACS variants were also judged as the intended emotions, as were a number of other proposed variants. Both signal and intensity clarities were individually associated with judgment-agreement rates; when their inter-relationships were taken into account.  However, signal clarity independently predicted agreement rates, but intensity clarity did not. The presence or absence of specific AUs appeared to be more important to agreement rates than their intensity levels, with the exception of the relationship between AU 12 and agreement rates for judgments of joy.

The data provided in this study highlights which expressions and AUs are associated with emotion judgments and thus are the likely candidates to be considered as signals of either modified innate programs or an appraisal process.

The current findings also demonstrate that signal clarity derived from combinations of specific AUs predicts emotion judgment-agreement rates, suggesting that signal clarity be taken into account in theories and studies of the role of context in emotion perception

To read more on Drs. Matsumoto & Hwang’s other research projects  click here.