On the role of horizontal structure in human face identification

Abstract

The human visual system must quickly and accurately deploy task-and-object-specific processing to successfully navigate the environment, which suggests several interesting research questions: What is the nature of these strategies? Are they flexible? To what extent is this behaviour optimal given the natural statistics of the environment? In this thesis, I explored these questions using human faces, a complex and dynamic source of socially relevant information that we encounter throughout our lives. Specifically, I conducted several experiments examining the role of horizontally-oriented spatial frequency components in face identification. In Chapter 2, I use computational modelling to demonstrate that the structure conveyed by these components is maximally diagnostic for face identity, and show that selective processing of this structure predicts both face identification performance and the face inversion effect. In Chapter 3, I quantify the bandwidth utilized by human observers and relate this sampling strategy to the information structure of face stimuli. In Chapter 4, I show that the selective sampling described in Chapters 2 and 3 is driven by information from the eyes. Finally, in Chapter 5, I show that the impaired horizontal selectivity associated with face inversion is enhanced by practice identifying inverted faces. Together, these experiments characterize a stimulus with differentially diagnostic information sources that, through experience, becomes selectively processed in a manner associated with task performance. These results contribute to our understanding of expert object processing and may have implications for observers experiencing face perception deficits.