Spontaneous use of gesture sequences in orangutans

Great apes use gestures flexibly across different contexts and with a considerable degree of individual variability. However, little is still known about whether great apes combine gestures to increase the efficacy of their communicative attempts – either by anticipatorily attracting the attention of the recipient towards themselves or by continuing to gesture in case the recipient does not respond. The few existing studies are not consistent in their conclusions. The present study thus aims to contribute to this discussion by providing a systematic investigation of gesture sequences of 16 captive orangutans. Our results showed that 20% of their gestures were part of a sequence and consisted mostly of combinations of two gestures with the majority representing repetitions of the same gesture. In addition, senders continued to gesture regardless of whether recipients responded to the initial gesture, they did not use particular gestures at the beginning of a sequence to attract the attention of recipients, and they did not switch to more efficient gestures in case the recipient did not respond. These findings therefore do not support the assumption that orangutans’ use of gesture sequences reflects goal directedness in achieving a particular goal, but may rather be the result of the arousal of the gesturing individual in particular contexts, such as play.