The hand-on gesture in gorillas (Gorilla gorilla)

The gestural repertoire of captive gorillas contains the so-called “hand-on” (or “pat-off”) gesture in which one animals puts its flat hand on top of another’s head, which often leads to cessation of the receiver’s previous activity. We investigate the origins of this gesture and developmental aspects of gesture creation. We further analyze gesture form and use in relation to the age of the sender with special consideration of the reaction of the receiver to better explain the function of the hand-on. The focus of the study is to compare this gesture across different age groups in gorillas in regard to both production and reception and to get insights into possible origins of the gesture.