Cross-adaptation Of Facial Weight And Expression:A Behavioral And ERP Study

Overweight has become very common all over the world.Being overweight not just has an implication of physical health problems but also has an implication of psychosocial consequences.For example,overweight individuals are more likely to be perceived as less attractive in social interactions.Previous studies have revealed a closely association between weight judgments and facial expression judgments.On the one hand,the weight of a face affects how its facial expression is perceived;on the other hand,facial expressions also affect how the weight of their faces is perceived.Based upon these findings,we hypothesized that the perception of body weight and emotion in faces may share some neural mechanisms.Thus,using a psychophysical method and event-related potential(ERP)technology,the current study aimed to investigate whether body weight and emotion reflected by human face could share common neural mechanisms by virtue of a cross-category paradigm.The aim of Experiment 1 was to explore whether there was a cross-adaptation between facial information about overweight,thin,and normal-weight and facial information about happy and angry.Experiment 1therefore used the visual adaptation paradigm to explore whether adaptation to overweight,thin,and normal-weight faces could lead to bias in the judgment of subsequent emotionally ambiguous test stimuli.The results of Experiment 1have shown that the adaptation of overweight faces leads us to think that the subsequent test stimulation is more likely to be happy.That is to say,according to the classic aftereffect of emotional adaptation,our overweight facial stimulation is considered to be negative in the emotional dimension.However,we found that after the adaptation of thin faces,there was no deviation in the judgment of test stimuli.In order to verify that the result of Experiment 1 is not caused by low-level features such as external shape contour of adaptive stimulus,we conducted Experiment 2.Experiment 2 used an ellipse of the same size as the facial stimulus in Experiment 1 as the adaptive stimulus,while the test stimulus and Experiment 1 remained unchanged.The results showed that there was no difference in the adaptation of the three sizes of ellipses in the subsequent test stimuli.Therefore,the results of Experiment 2 confirmed that the results of Experiment 1 are reliable.To explore whether adaptation to emotional stimuli could lead to an effect on subsequent test stimuli for weight ambiguity,we conducted Experiment 3.The adaptive and test stimuli in Experiment 3 were opposite to those in Experiment 1.Our results suggest that adaptation to the emotional stimulus of angry does make us more likely to judge a subsequent test stimulus with a fuzzy weight as thin.Finally,in order to study the stage of cross-adaptation and neural correlation proved in Experiment 1,we conducted Experiment 4.In view of the non-significant thin condition in Experiment 1,we only used two adaptive stimuli of overweight and normal weight in Experiment 4.In addition,in order to eliminate the influence of low-level features in the later stage,we made phase randomized control conditions for these two adaptive stimuli.The behavioral results showed that,compared with normal adaptation,the participants tended to make a happy response to the test stimulus after adaptation to overweight conditions.In other words,overweight faces are more likely to be seen as angry.This finding is consistent with the results of our Experiment 1,indicating that there is cross category adaptation between overweight and emotional expression,and they may share some common neural mechanisms.For ERP results,we found potential neural correlates of perceptual bias.As expected,after being exposed to overweight,N170 amplitude for emotional test stimuli was significantly greater than normal within 160-220 msec.Our results provided evidence for the cross-adaptation between overweight and emotional expressions and its neural correlates.In sum,combining adaptation paradigms and event-related potential techniques,the current findings demonstrated that there was a cross-adaptation effect between body weight and emotion reflected by human face.