Warsaw set of emotional facial expression pictures: a validation study of facial display photographs

Abstract

Emotional facial expressions play a critical role in theories of emotion and figure prominently in research on almost every aspect of emotion. This article provides a background for a new database of basic emotional expressions. The goal in creating this set was to provide high quality photographs of genuine facial expressions. Thus, after proper training, participants were inclined to express "felt" emotions. The novel approach taken in this study was also used to establish whether a given expression was perceived as intended by untrained judges. The judgment task for perceivers was designed to be sensitive to subtle changes in meaning caused by the way an emotional display was evoked and expressed. Consequently, this allowed us to measure the purity and intensity of emotional displays, which are parameters that validation methods used by other researchers do not capture. The final set is comprised of those pictures that received the highest recognition marks (e.g., accuracy with intended display) from independent judges, totaling 210 high quality photographs of 30 individuals. Descriptions of the accuracy, intensity, and purity of displayed emotion as well as FACS AU's codes are provided for each picture. Given the unique methodology applied to gathering and validating this set of pictures, it may be a useful tool for research using face stimuli. The Warsaw Set of Emotional Facial Expression Pictures (WSEFEP) is freely accessible to the scientific community for non-commercial use by request at http://www.emotional-face.org.

Keywords: basic emotions; emotion; emotion recognition; face perception; facial expression recognition; facial expressions of emotion; pictures; validation.

Figure 1

Examples of photographs from WSEFEP with received ratings. Each mark represents a rating from a single participant. The letters indicate: N, number participants evaluating picture; A, accuracy of displayed emotion; P, purity of displayed emotion, and I, intensity of displayed emotion.

Figure 2

Ratings distribution for facial expression of anger, disgust, fear, joy, sadness, surprise, and neutral faces from WSEFEP.

Figure 3

Examples of purity and intensity scores. Purity scores were based on relative difference of angles between the radius line directly crossing the middle of the field of a given emotion field (e.g., fear) and the radius line crossing through the answer point. In this example the answer “A” received 1 point as it is located directly on the line. Answer “B” received 5 point as α₁ is 5 smaller than α. Answer “C” received 0 points as it is located outside of the emotion field (displayed emotion is not recognized as intended). Intensity scores were calculated as the relative distance of segment “ab” starting from point “a” (border of internal wheel labeled neutral scored 0) to the wheel border—point “b” (scored 1). Thus, answer “A” was scored 58 on the intensity scale.