The Role of symmetry and facial expressions of emotions in evaluation of attractiveness and perceived symmetry : an eye tracking study

Hepsomalı, Pırıl
In social interaction, faces convey plenty of information such as gender, age, attractiveness and expressions of emotions. Amongst these cues, attractiveness and facial expressions of emotions are considered more substantial, since processing and evaluation of such information rapidly has adaptive relevance in order to avoid or approach. One of the indicators of attractiveness, symmetry, is preferred by many species and it is known that symmetrical faces are rated as more attractive by humans. Moreover, facial expressions of emotions contribute to attractiveness judgements. The aim of the current study is to investigate attractiveness and perceived symmetry judgements for symmetric or original (asymmetric) facial expressions while physiological responses are collected through an eye-tracking system. We used a subset of expressions and images from the Karolinska Directed Emotional Faces (KDEF) as stimuli. The experimental conditions consisted of original and bi-laterally symmetric forms of face images. Three facial expressions are chosen from the KDEF with neutral, highly arousing positive (surprise) and highly arousing negative (angry) facial expressions. The subjects are asked to evaluate the face images in two phases: phase I consisted of attractiveness judgement and phase II consisted of symmetry judgement, both on a 9 point Likert scale. During experimentation, The TOBII T120 eye tracker that has pupillary response collection ability is used to facilitate interpretation of fixation duration as well as pupil diameter responses in terms of cognitive load, attention, and arousal. In this study, when the subjects judged attractiveness, the finding that symmetrical images are rated as more attractive is replicated. Moreover, we found that fixation durations to symmetrical images are longer while pupil diameters are smaller with respect to their original counterparts. Since, longer fixation durations are related with attention, and focused attention constricts pupil, we conclude that symmetrical faces capture attention during judgement of attractiveness. While considering emotions, neutral facial expressions were rated as more attractive than angry and surprised facial expressions. Furthermore, fixation durations and pupillary diameters are observed to be longer and bigger for highly arousing affective stimuli. These findings implicate that the survival value of the stimuli (i.e. arousal) play an important part in initiating physiological responses during attractiveness judgement. Physiological responses did not differ when subjects were asked to judge symmetry of the facial stimulus instead of their attractiveness leading into a conclusion that attractiveness judgements involve cognitive processes that interact with emotion compared to symmetry judgements, while symmetry judgements are limited to automatic processes. To the best of our knowledge this is the first study that investigates subjective judgments of faces under different symmetry and facial expression conditions along with physiological responses such as eye fixation duration and pupillary response.
Citation Formats
P. Hepsomalı, “The Role of symmetry and facial expressions of emotions in evaluation of attractiveness and perceived symmetry : an eye tracking study ,” M.S. - Master of Science, Middle East Technical University, 2013.