Author: Stephanie McGowan
McGowan, Stephanie, 2025 Alexithymia and Emotional Face Detection: Testing the Anger Superiority Effect, Flinders University, College of Education, Psychology and Social Work
Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact copyright@flinders.edu.au with the details.
Alexithymia is a dimensional personality trait primarily associated with difficulty identifying and describing emotions. While present in roughly 10% of the general population, its prevalence is significantly higher in clinical groups, including individuals with autism spectrum disorder, depression, social anxiety, schizophrenia, anorexia nervosa, and substance use disorders. Although prior research has examined how alexithymia affects emotional face processing, little is known about its role in the detection of social threats.
Visual search studies in the general population have demonstrated an anger superiority effect, whereby angry faces are detected more quickly and accurately than other emotional expressions. However, the findings have been inconsistent. This thesis investigates whether alexithymia modulates the anger superiority effect using variations of the face-in-the-crowd paradigm across six studies.
Studies 1A-1C used schematic facial stimuli to compare search performance across low, medium, and high alexithymia conditions. Study 1A (angry vs. happy faces) found that participants with higher alexithymia responded faster and with flatter search slopes, but with comparable accuracy. An anger superiority effect was observed overall. Study 1B (angry vs. sad faces) did not replicate these alexithymia-related differences but again supported the anger superiority effect. Study 1C included all three emotions and again supported the anger superiority effect, though no differences emerged across alexithymia levels.
Study 2 employed photographic stimuli to increase ecological validity. No anger superiority effect or alexithymia-related differences were found. Study 3 tested non-emotional visual search using numeric distractors (i.e., finding a “2” among “5”s) and found no differences across alexithymia conditions, suggesting similar general visual search performance across alexithymia severities.
Study 4 reintroduced schematic faces and included electroencephalography (EEG) to assess attentional allocation on a neural level using the N2pc component. Behavioural data again
supported the anger superiority effect, while EEG results showed faster N2pc onset for angry targets. No neural or behavioural differences were observed between the alexithymia conditions.
Across all studies, both frequentist and Bayesian analyses were used to evaluate effects and to explore the robustness of findings. Overall, the results suggest that higher levels of alexithymia do not impair emotional face detection or reduce the anger superiority effect. The anger superiority effect was reliably observed with schematic stimuli but not with photographic images, indicating the effect may vary based on the complexity of emotional stimuli. These findings suggest that the deficits in facial emotion processing associated with alexithymia either occur at a later stage of processing or are potentially overstated in the current alexithymia literature. In relation to the anger superiority effect, while evidence was found supporting its existence, the failure to replicate this effect using photographic stimuli indicates that it may be sensitive to stimulus type and complexity. Recommendations for future research are provided based on the findings.
Keywords: alexithymia, anger superiority effect, emotional face detection, visual search, N2pc, face-in-the-crowd, threat detection
Subject: Psychology thesis
Thesis type: Doctor of Philosophy
Completed: 2025
School: College of Education, Psychology and Social Work
Supervisor: Professor Mike Nicholls