Examining Categorical Perception of Emotional Facial Expressions

Abstract

Individuals perceive emotional facial expressions in categories. Specifically, for basic emotional expressions, discrimination performance is better for pairs of stimuli that fall in either side of a perceptual category boundary than for those within a perceptual category. In this thesis I have examined categorical perception of emotional facial expressions from a number of different perspectives. In Chapter 2, I found in two experiments that categorical perception of emotional facial expressions of a robust phenomenon with a few consistent individual differences. There findings highlight some of the important caveats that categorical perception researchers face, not only in the area of emotional facial expressions, but across domains as well. In Chapter 3 I show that context has an effect on the visual perception of emotional facial expressions. A surprise-fear continuum was perceived categorically only in the case in which a context story was provided for the surprise face. In Chapter 4 I demonstrate categorical perception of a happy-sad continuum in 3.5-year-olds. This is an important study in development because the current literature is limited by studies that do not compare identification and discrimination performance in these age groups. The experiment in this chapter uses both identification and discrimination tasks and compares the results of 3.5-year-olds to adults who do the exact same task. The results suggest that 3.5-year-olds perceive happy and sad expressions as adults do, categorically. In Chapter 5 I develop a powerful new methodology for the study of the category boundary using non-verbal methods. This investigation with emotional facial expressions shows it can be reliably used to identify category boundary information in adults. Perception of emotional facial expressions is an essential part of successful social cognition, and the phenomenon of categorical perception specifically allows individuals to quickly and accurately respond to expressions. The research in this thesis is a further step in understanding the processes that allows individuals to be successful in a social environment.