Understanding communicative intentions and semiotic vehicles by children and chimpanzees

Developmental and comparative studies of the ability to understand communicative intentions using object-choice tasks raise questions concerning the semiotic properties of the communicative signals, and the roles of rearing histories, language and familiarity. We adapted a study by Tomasello, Call, and Gluckman (1997), in which a “helper” indicated the location of a hidden reward to children of three ages (18, 24, and 30 months) and to four chimpanzees, by means of one of four cues: Pointing, Marker, Picture and Replica. For the chimpanzees, we controlled for familiarity by using two helpers, one unfamiliar and one highly familiar. Even 18-months performed well on Pointing and Marker, while only the oldest group clearly succeeded with Picture and Replica. Performance did not correlate with scores for the Swedish Early Communicative Development Inventory (SECDI). While there were no positive results for the chimpanzees on the group level, and no effect of familiarity, two chimpanzees succeeded on Pointing and Marker. Results support proposals of a species difference in understanding communicative intentions, but also highlight the need to distinguish these from the complexity of semiotic vehicles and to consider both factors.