Objectives: The current study sought to contrast predictions of social versus cognitive influences on face perception. To study how social personality traits influence face-related activity, the relationship between gamma synchrony and social motivation was examined. The social motivation hypothesis would predict significant correlations between gamma synchrony and extraversion, while cognitive accounts would predict no relationship.
Methods: 96 typically-developing adults (34 male) were pre-screened with the Eysenck Personality Questionnaire Revised Short Scale (EPQ-R) for high or low (+/- 1 SD) scores on the extraversion subscale. 24 extreme scorers (14 extraverts, 10 introverts) viewed 60 trials each of upright and inverted faces, while EEG was recorded with a 128-channel Geodesic Sensor Net. EEG signals were decomposed to the gamma frequency band (30-50 Hz) using wavelet analysis based on 4-6 cycles, a 148 ms window size and 547.2 ms epochs, including a -25.6 ms baseline. Synchrony based on phase difference was calculated between all channel pairs and measured between 0 and 1, where 1 indicates two perfectly synchronized signals.
Results: ERP results indicated that the inversion effect significantly interacted with personality type: F (1, 22) = 5.11, p = .03, MSE = 0.86, η2partial = .19. Paired-sample t-tests revealed a significant difference in N170 amplitude between upright and inverted faces for the extraversion group, t (13) = 4.43, p = .001, but no significant difference for the introversion group. Gamma analyses in progress reveal right-lateralized frontal/posterior coherence around 270 ms post-stimulus onset. We predict significantly greater synchrony in this time window in extroverted individuals.
Conclusions: Results reflect the influence of social drive on face perception in typical development. This is the first study to demonstrate association between evoked gamma synchrony to faces and social personality traits. These findings parallel relationships observed in ASD and are consistent with the predictions of social motivation models of ASD.