Given that most research examining prosocial behaviours with regard to nonhuman apes is focusing on chimpanzees and studies including the bonobo are scarce, in this study we are specifically comparing bonobos with chimpanzees. Chimpanzees and bonobos are differing on several types of behaviours such as social tolerance and stress reactivity, which are thought to influence expressions of prosociality [1, 2]. Moreover, researchers found differences between bonobos and chimpanzees in brain structures related to empathic abilities [2]. It is yet unknown whether such structural differences also result in differences in overt behaviours, and whether empathy is underlying prosociality also in nonhuman primates. In this study, six bonobo and chimpanzee pairs are presented with an instrumental helping design through which it is examined whether the helper of each pair is transferring tools to a conspecific. The level of cognitive complexity underlying such helping is additionally examined. More specifically, if the helpers are able to demonstrate a self-other distinction, hence, understand that the other might need a different tool to the one currently needed by themselves. Behavioural measures are taken to examine their relationship to the frequency of tool sharing. During the first testing phase, prosocial acts will have no benefit for the helper. However, during the second testing phase the helper will acquire the reward only through transferring a correct tool to the conspecific. For the third testing phase the procedure will be switched back to the initial set up, resulting in an ABA design. We hypothesize that the frequency of tool transfers will increase when the helper is benefiting from such cooperation, and will decrease again when no benefit results from helping. This study is currently ongoing.