Categorical perception of vocal emotion expressions

Continua of vocal emotion expressions, ranging from one expression to another, were created using speech synthesis. Each emotion continuum consisted of expressions differing by equal physical amounts. In 2 experiments, subjects identified the emotion of each expression and discriminated between pairs of expressions. Identification results show that the continua were perceived as 2 distinct sections separated by a sudden category boundary. Also, discrimination accuracy was generally higher for pairs of stimuli falling across category boundaries than for pairs belonging to the same category. These results suggest that vocal expressions are perceived categorically. Results are interpreted from an evolutionary perspective on the function of vocal expression.