Uncertainty management in type-2 fuzzy face-space for emotion recognition

Manifestation of a given emotion on facial expression is not always unique, as the facial attributes in different instances of similar emotional experiences may vary widely. When a number of facial attributes are used to recognize the emotion of a subject, the variation of individual attributes together makes the problem more complicated. This variation is the main source of uncertainty in the emotion recognition problem, which has been addressed here in two steps using type-2 fuzzy sets. First a type-2 fuzzy face-space is constructed with the background knowledge of facial features of different subjects for different emotions. Second, the emotion of the unknown subject is determined based on the consensus of the measured facial features with the fuzzy face-space. The face-space comprises both primary and secondary membership distributions. The primary membership distributions here have been constructed based on the highest frequency of occurrence of the individual attributes. Naturally, the membership values of an attribute at all except the point of highest frequency of occurrence suffer from inaccuracy, which has been taken care of by secondary memberships. An algorithm for the evaluation of the secondary membership distribution from its type-2 primary counterpart has been proposed. The uncertainty management policy adopted using general type-2 fuzzy set has a classification accuracy of 96.67% in comparison to 88.67 % obtained by interval type-2 counterpart only.