Chapter 2. Addressing the problems of intentionality and granularity in non-human primate gesture

Any study of communicative gesture must identify which movements are purposeful (intentionality) and which examples of movements should be grouped into a single gesture (granularity). Where researchers studying human gesture are aided by linguistic context, researchers studying non-human primates must rely on their subjects’ movements alone to address these questions. We propose an approach to intentionality and granularity in non-human primate gesture based first on the possibility that only some, but not all individuals that use particular movements do so as intentional gestures, and second on the premise that gestures found to have specific meanings reflect real-world distinctions made by the animals. We apply this approach to the behavior of 28 captive orangutans and identify 64 distinct gestures, 29 of which have specific, predictable meanings.