Changing the question “Are faces special?” to “In what way are faces special?” : An investigation of face recognition and perceptual learning.

Abstract

This thesis investigates the new possibility that both expertise and face specific mechanisms play a role in face recognition, which have conventionally been treated as two contending notions competing with one another (e.g., Yin, 1969, Diamond & Carey, 1986). Results will be provided from behavioral and transcranial-Direct Current Stimulation (tDCS) experiments using face stimuli and prototype-defined checkerboard stimuli that have been used in a line of research that has demonstrated a role for expertise via perceptual learning in face recognition (McLaren, 1997; Civile, Zhao, et al., 2014; Civile, Verbruggen, et al., 2016; Civile, McLaren, et al., 2018). Each of the 7 chapters in this thesis contribute to the further understanding of the role perceptual learning plays in face recognition, and the extent to which face specific processing is additionally involved. Chapter 1 discusses the background literature and key theories/debates in the face recognition research to set the scene. Chapter 2 compares the effects of tDCS on the face inversion and checkerboard inversion effect. It was this difference in the tDCS-induced decrement in the inversion effect between the two stimuli that instigated the suggestion of an additional component alongside perceptual learning, that is possibly face specific. The experiments reported here contributed to Civile, Quaglia, Waguri, Ward, McLaren, and McLaren (2021). Chapter 3 sets out to identify what the face specific component is, and whether this could be attributed to configural/holistic processing as indexed by the composite face effect. As a first step in testing this, the congruency effect (a component of the composite effect) was investigated with checkerboard stimuli. This experiment contributed to Waguri, McLaren, McLaren, and Civile, (2021). Chapter 4 extends the work in Chapter 3, and sets out to comparatively investigate the composite effect in checkerboards and faces. This work contributed to Waguri, McLaren, McLaren, and Civile (2022). Chapter 5 investigated the role of proactive interference, as this was found to be contributing to the results on the composite effect in Chapter 4. This was investigated via the inversion effect and assessed to see if it would affect the perceptual learning interpretation of the role tDCS plays in modulating face recognition. Chapter 6 explores the behavioral and electrophysiological effects of the tDCS procedure (as used in Chapter 2), in circumstances where harmful generalization induced by Thatcherized faces has influenced the inversion effect for “normal” faces. This work contributed to Civile, Waguri, McLaren, Cooke, and McLaren, (under review). Finally, Chapter 7 summarizes the chapters and discuss the implications of the work for the face recognition literature and the key debates regarding the underlying mechanisms.