Abstract
BACKGROUND: Although gestural communication is widespread in primates, few studies focused on the cognitive processes underlying gestures produced by monkeys. METHODOLOGY/PRINCIPAL FINDINGS: The present study asked whether red-capped mangabeys (Cercocebus torquatus) trained to produce visually based requesting gestures modify their gestural behavior in response to human's attentional states. The experimenter held a food item and displayed five different attentional states that differed on the basis of body, head and gaze orientation; mangabeys had to request food by extending an arm toward the food item (begging gesture). Mangabeys were sensitive, at least to some extent, to the human's attentional state. They reacted to some postural cues of a human recipient: they gestured more and faster when both the body and the head of the experimenter were oriented toward them than when they were oriented away. However, they did not seem to use gaze cues to recognize an attentive human: monkeys begged at similar levels regardless of the experimenter's eyes state. CONCLUSIONS/SIGNIFICANCE: These results indicate that mangabeys lowered their production of begging gestures when these could not be perceived by the human who had to respond to it. This finding provides important evidence that acquired begging gestures of monkeys might be used intentionally.