Tennis grunts communicate acoustic cues to sex and contest outcome

Despite their ubiquity in human behaviour, the communicative functions of nonverbal vocalisations remain poorly understood. Here, we analysed the acoustic structure of tennis grunts, nonverbal vocalisations produced in a competitive context. We predicted that tennis grunts convey information about vocalizer and context, similar to nonhuman vocal displays. Specifically, we tested whether the fundamental frequency (F0) of tennis grunts conveys static cues to a player’s sex, height, weight, and age, and covaries dynamically with tennis shot type (a proxy of body posture) and the progress and outcome of male and female professional tennis contests. We also performed playback experiments (using natural and resynthesised stimuli) to assess the perceptual relevance of tennis grunts. The F0 of tennis grunts predicted player sex, but not age or body size. Serve grunts had higher F0 than forehand and backhand grunts, grunts produced later in contests had higher F0 than those produced earlier, and grunts produced during contests that players won had a lower F0 than those produced during lost contests. This difference in F0 between losses and wins emerged early in matches, and did not change in magnitude as the match progressed, suggesting a possible role of physiological and/or psychological factors manifesting early or even before matches. Playbacks revealed that listeners use grunt F0 to infer sex and contest outcome. These findings indicate that tennis grunts communicate information about both vocalizer and contest, consistent with nonhuman mammal vocalisations.