Table 1. Criteria used for identifying intentional production of communicative signals, as outlined in the study of great ape gestures [19]–[36].
Criteria | Explanation |
Social use | The signal is directed at a recipient. This can be assessed at various levels: |
1. Presence/absence audience effect: the signal is only produced in the presence of a recipient. | |
2. Composition of audience: the signal is only produced in the presence of certain recipients (e.g., kin, dominants, friends) | |
3. Behaviour of audience: signal production is contingent on the behaviour of the recipient | |
Sensitivity to attentionalstate of recipient* | Visual signals are only produced in the field of view of recipients. If signaller does not have a recipient’s visual attention, tactile or auditory signals should be produced. This can also be considered a level (3) audience effect. |
Manipulation of attentional state of recipient* | Before a visual signal is produced, attention-getting behaviours are directed towards a recipient who is not visually attending to the signaller. |
Audience checking andgaze alternation | Signaller monitors the audience and visually orients towards the recipient before producing a signal. If a third entity is involved, gaze alternation may occur between recipients and this entity. |
Persistence or elaboration | Goal-directed signalling shown by repetition of the same signal (persistence), or production of different signals (elaboration) until the desired goal is met. |
indicates applicable only to visual signals and therefore not relevant for vocal production.