ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France; Equipe Cognition Auditive et Psychoacoustique, CRNL, CNRS, Inserm, University Lyon 1, Bron 69500, France; Corresponding author
Mounia Kehy
ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France
Nicolas Boyer
ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France
Aurélie Pradeau
ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France
Léo Papet
ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France
Etienne Gaudrain
Equipe Cognition Auditive et Psychoacoustique, CRNL, CNRS, Inserm, University Lyon 1, Bron 69500, France
Nicolas Grimault
Equipe Cognition Auditive et Psychoacoustique, CRNL, CNRS, Inserm, University Lyon 1, Bron 69500, France
Nicolas Mathevon
ENES Bioacoustics Research Laboratory, CRNL, CNRS, Inserm, University of Saint-Etienne, Saint-Etienne 42100, France; Institut Universitaire de France, Paris, France
Summary: Rapidly sorting the information contained in a stream of stimuli is a major challenge for animals. One cognitive mechanism for achieving this goal is categorization, where the receiving individual considers a continuous variation of a stimulus as belonging to discrete categories. Using playback experiments in a naturalistic setup, here we show that crocodiles confronted with an acoustic continuum ranging from a frog call to a crocodile call classify each acoustic variant into one of these two categories, establishing a meaningful boundary where no acoustic boundary exists. With GO/NO-GO experiments, we then observe that this boundary is defined along the continuum following learning. We further demonstrate that crocodilians rely on the spectral envelope of sounds to categorize stimuli. This study suggests that sound categorization in crocodilians is a pre-wired faculty allowing rapid decision-making and highlights the learning-dependent plasticity involved in defining the boundary between sound categories.
