Does sympathy motivate prosocial behaviour in great apes?

Abstract

Prosocial behaviours such as helping, comforting, or sharing are central to human social life. Because they emerge early in ontogeny, it has been proposed that humans are prosocial by nature and that from early on empathy and sympathy motivate such behaviours. The emerging question is whether humans share these abilities to feel with and for someone with our closest relatives, the great apes. Although several studies demonstrated that great apes help others, little is known about their underlying motivations. This study addresses this issue and investigates whether four species of great apes (Pongo pygmaeus, Gorilla gorilla, Pan troglodytes, Pan paniscus) help a conspecific more after observing the conspecific being harmed (a human experimenter steals the conspecific's food) compared to a condition where no harming occurred. Results showed that in regard to the occurrence of prosocial behaviours, only orangutans, but not the African great apes, help others when help is needed, contrasting prior findings on chimpanzees. However, with the exception of one population of orangutans that helped significantly more after a conspecific was harmed than when no harm occurred, prosocial behaviour in great apes was not motivated by concern for others.

Figure 1. Proportion of trials with stick transfers.

Orangutans transferred more sticks in the Experimental conditions (Take and Give) than in the Control conditions (Control 1: No food and Control 2: No victim), while the occurrence of stick transfers in chimpanzees did not differ between the Experimental and Control conditions.

Figure 2. Mean frequencies of arousal behaviours of the victim during the observation phase.

There was a significant interaction between condition and species (p = 0.011), and a main effect of condition (p = 0.08) and of species (p = 0.015). African great apes, but not orangutans showed more arousal behaviour when interacting with the experimenter in the observation phase of the Take compared to the Give condition (each lasting 60 seconds). Error bars indicate SD.

Figure 3. Mean frequencies of arousal behaviours of the victim during the prosocial phase.

There was a significant interaction between condition and species (p = 0.021) and a main effect of species (p = 0.001), but no main effect of condition (p = 0.859). Bonobos and chimpanzees showed more arousal behaviours in the prosocial phases of the Take and Give condition (each lasting 180 seconds) than orangutans and gorillas. However, only gorillas and bonobos displayed marginally more arousal in the prosocial phase of the Take condition compared to the Give condition. Error bars indicate SD.