Lateralisation of affective perception: the impact of unilateral brain damage on the perception of facial emotion

Submission note: A thesis submitted in partial fulfilment for the requirement of the degree of Doctor of Clinical Neuropsychology to the School of Psychological Science, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.

The first Chapter provides a general introduction to the area by reviewing and discussing the available literature on how the brain is lateralised to perceive positive and negative emotions expressed in faces. Chapter two systematically integrated the available research findings to determine how the brain is lateralised to perceive positive and negative facial expressions, using meta-analysis. Overall, the meta-analytic results demonstrated supported for a model whereby negative emotion is controlled by the right hemisphere and both hemispheres process positive emotion from faces. Chapter three included detailed methodological information of the new clinical investigation that comprised Studies two and three reported in the papers in Chapters four and five. Chapter four further assessed the extent to which right and left cerebral damage impact the perception of positive and negative emotion from faces. More specifically, the influence of potential moderators, including participant gender, injury aetiology, injury chronicity, the number of emotions used within a task, and task type, were controlled. Overall, no group differences in the ability to accurately perceive facial expressions according to valence were found, which suggests that both hemispheres process positive and negative facial expressions. Chapter five examined the contributions of configural and featural processing strategies to the left and right hemisphere' affective perception. Overall, no group differences in the processing strategies used to perceive affective faces according to valence were found, suggesting that these processing strategies do not underlie hemispheric differences in the perception of positive and negative emotions. While the findings from each Study are discussed in detail in the discussion of each chapter, the final chapter provides a summary and integration of the major findings in this thesis. The limitations of the current series of research projects and directions for future research is also discussed.