Temporal organisation of action in baboons: comparisons with the temporal segmentation in chimpanzee and human...

The durations of sequences of functionally related movements, or action units, were analysed in the baboons Papio hamadryas and Papio anubis. Action units are completed within a narrow time span or temporal segment as found previously in pongids and humans. Although the temporal segmentation is generally similar in the three species, baboons show several differences from both chimpanzees and humans. Firstly, their temporal segments are shorter and less variable and the different sorts of action units, such as hand-body contact or interactions with an object, show slight but significant differences in duration. Secondly, those action units that consist of movements occurring twice last almost twice as long as action units without repetitions. In contrast, in chimpanzees and humans, repetition of a set of movements compresses the first set so that the action unit duration does not increase. This is thought to be due to a form of presyntactical motor planning. Its absence in baboons shows that presyntactical motor planning is confined to those primates with language ability and so provides further support for a relationship between motor and language systems.