Hearing natural animal sounds: Human emotional valence appraisal is strongly linked with auditory roughness perception

Natural animal sounds can be perceived as "harsh" or "buzzy"-sound descriptions known as auditory roughness. In this study, the association between the human emotional appraisal of animal vocalizations and the perceived roughness was examined across three sound categories-mammals, birds, and insects. Ninety 1-s vocalizations (30 per category) were rated online by two independent groups: one judged perceived roughness, the other judged valence and arousal. Perceived roughness showed a strong negative correlation with valence (rougher sounds were judged more negatively). No clear link between roughness and arousal emerged (no correlation for birds and mammals, and a small one for insects) probably because of the homogeneity of the arousal ratings. Acoustic analyses showed that a variability measure derived from the modulation power spectrum tracked perceived roughness and, inversely, valence within and across categories. Together, these results indicate that humans systematically interpret rough sounds, irrespective of their source species, as cues of negative valence. We propose that roughness is an ecologically meaningful auditory code that drives emotional responses to animal sounds in humans.