Sounds of emotion: production and perception of affect-related vocal acoustics.
In his writing Darwin emphasized direct veridical links between vocal acoustics and vocalizer emotional state. Yet he also recognized that acoustics influence the emotional state of listeners. This duality-that particular vocal expressions are likely linked to particular internal states, yet may specifically function to influence others-lies at the heart of contemporary efforts aimed at understanding affect-related vocal acoustics. That work has focused most on speech acoustics and laughter, where the most common approach has been to argue that these signals reflect the occurrence of discrete emotional states in the vocalizer. An alternative view is that the underlying states can be better characterized using a small number of continuous dimensions such as arousal (or activation) and a valenced dimension such as pleasantness. A brief review of the evidence suggests, however, that neither approach is correct. Data from speech-related research provides little support for a discrete-emotions view, with emotion-related aspects of the acoustics seeming more to reflect to vocalizer arousal. However, links to a corresponding emotional valence dimension have also been difficult to demonstrate, suggesting a need for interpretations outside this traditional dichotomy. We therefore suggest a different perspective in which the primary function of signaling is not to express signaler emotion, but rather to impact listener affect and thereby influence the behavior of these individuals. In this view, it is not expected that nuances of signaler states will be highly correlated with particular features of the sounds produced, but rather that vocalizers will be using acoustics that readily affect listener arousal and emotion. Attributions concerning signaler states thus become a secondary outcome, reflecting inferences that listeners base on their own affective responses to the sounds, their past experience with such signals, and the context in which signaling is occurring. This approach has found recent support in laughter research, with the bigger picture being that the sounds of emotion-be they carried in speech, laughter, or other species-typical signals--are not informative, veridical beacons on vocalizer states so much as tools of social influence used to capitalize on listener sensitivities.