Search

Faces are a unique type of stimulus for humans. As such, they are processed differently to other types of stimuli like houses or objects. In the past, laboratory based testing has been used to examine the neural correlates of human face processing. However, viewing faces in a laboratory differs considerably from how it occurs the real world. This thesis examines the neural mechanisms underlying the processing of face images in a naturalistic setting. A custom-design mobile brain and body imaging technique was used to explore the neural mechanisms governing naturalistic face processing. Simultaneous mobile electroencephalography (EEG) and eye-tracking data was recorded from participants while they freely viewed images presented in a mock art gallery. The synchronisation of both data streams allowed us to analyse the EEG signal by time-locking markers to naturally occurring visual events captured by the eye tracker. Using this methodology the effects of emotion, familiarity and body posture on the face-sensitive N170 ERP component were investigated. The findings demonstrated, for the first time, the possibility of detecting face-specific brain potentials in freely moving, unrestricted subjects during passive viewing of images, as well as during active interactions with another person. The results present the effects of emotional valence on the N170 amplitude and replicate previous lab-based findings. Furthermore, the effects of body posture on early visual ERPs, but not the face-sensitive N170 contribute new insights to the face processing literature. Finally, the N170 component produced during a dyadic social interaction is described in relation to previous laboratory based reports. The experimental chapters present a novel methodology for recording mobile EEG signals as well as an adaptable experimental design that can be used in a wide variety of fields. The thesis demonstrates that EEG activity associated to the viewing static faces in laboratory conditions resemble those produced in real world environments as well as during natural social interactions. Moreover, the effects of emotional content on face processing were represented in the N170 component particularly, when disgusted faces were viewed.