What is intentional communication and how do you measure it?

Intentional communication (IC) is the display of communicative signals that are sensitive to the state of the receiver. Drawing from research into the communication of human infants, IC can be operationalized in accordance with several objective criteria for assessment. First, it is exhibited socially, an audience is required. Second, the signaler adjusts communication in accordance with the behavioral correlates of attention in the receiver. Third, when communication is about an entity or event that is spatially removed from both signaler and receiver, it is exhibited with gaze alternation between this distant entity and the receiver. Another way of stating this is that the visual orienting behavior of the signaler is under the stimulus control of both receiver location and the location of the distant entity. Fourth, if the putative goal of the communicative act is not achieved, the signaler will persist in communicating. Fifth, if initial signals fail to achieve the putative goal, the signaler will elaborate its communication. We present data from several studies of manual gestures in captive chimpanzees (Pan troglodytes) that demonstrates all five of these objective criteria for measuring IC. In human development, IC is of interest because there is a robust, widely replicated developmental transition at or near 12 months of age, in which babies begin to 'take charge' of communicative interactions, for example, through pointing. The evidence therefore suggests that these abilities to engage in joint attention are shared among humans and apes (and perhaps monkeys, as well), with relatively deep phylogenetic roots.