Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 12 (4), 587-97

Chimpanzees (Pan Troglodytes) Do Not Develop Contingent Reciprocity in an Experimental Task


Chimpanzees (Pan Troglodytes) Do Not Develop Contingent Reciprocity in an Experimental Task

Sarah Frances Brosnan et al. Anim Cogn.


Chimpanzees provide help to unrelated individuals in a broad range of situations. The pattern of helping within pairs suggests that contingent reciprocity may have been an important mechanism in the evolution of altruism in chimpanzees. However, correlational analyses of the cumulative pattern of interactions over time do not demonstrate that helping is contingent upon previous acts of altruism, as required by the theory of reciprocal altruism. Experimental studies provide a controlled approach to examine the importance of contingency in helping interactions. In this study, we evaluated whether chimpanzees would be more likely to provide food to a social partner from their home group if their partner had previously provided food for them. The chimpanzees manipulated a barpull apparatus in which actors could deliver rewards either to themselves and their partners or only to themselves. Our findings indicate that the chimpanzees' responses were not consistently influenced by the behavior of their partners in previous rounds. Only one of the 11 dyads that we tested demonstrated positive reciprocity. We conclude that contingent reciprocity does not spontaneously arise in experimental settings, despite the fact that patterns of behavior in the field indicate that individuals cooperate preferentially with reciprocating partners.


Fig. 1
Fig. 1
A schematic of the barpull apparatus. Two lexan trays were positioned on top of the other, with a vertical separation of approximately 45 cm. The actor could choose to pull, using a rope handle (thick dotted lines) either of the two barpulls (gray bars) forward to receive food (black circles). The recipient only received food if the actor pulled the level baited on the recipient’s side. The position of the ropes alternated from trial to trial, so each individual had the opportunity to pull on alternate trials. The actor and recipient were next to each other, separated by a mesh partition (thin dotted line). Here, the donor is on the right side of the mesh partition, the prosocial option is provided on the top level and the selfish option is provided on the bottom level
Fig. 2
Fig. 2
The distribution and conditional probability of actor’s responses given a behavior of partner on previous trial, b number of 1/1 choices made by partner in previous two trials, c number of 1/1 choices made by partner in previous three trials. The bars indicate 95% confidence intervals based on assuming independence only among dyads
Fig. 3
Fig. 3
The frequency of prosocial (1/1) choices over the course of the six sessions. The dashed horizontal line at 0.5 indicates chance levels of choosing the prosocial option over the selfish (1/0) option. Note that Y-axis scale ranges only from 45 to 55%

Similar articles

  • Chimpanzees Return Favors at a Personal Cost
    M Schmelz et al. Proc Natl Acad Sci U S A 114 (28), 7462-7467. PMID 28630319.
    Humans regularly provide others with resources at a personal cost to themselves. Chimpanzees engage in some cooperative behaviors in the wild as well, but their motivatio …
  • Chimpanzees Help Each Other Upon Request
    S Yamamoto et al. PLoS One 4 (10), e7416. PMID 19826478.
    These results provide further evidence for altruistic helping in chimpanzees in the absence of direct personal gain or even immediate reciprocation. Our findings addition …
  • Do Chimpanzees (Pan Troglodytes) Spontaneously Take Turns in a Reciprocal Cooperation Task?
    S Yamamoto et al. J Comp Psychol 123 (3), 242-9. PMID 19685965.
    Reciprocity is considered to be an explanation for altruism toward nonkin. Although there have been many theoretical studies and reciprocity is arguably prevalent in huma …
  • The Roots of Human Altruism
    F Warneken et al. Br J Psychol 100 (Pt 3), 455-71. PMID 19063815. - Review
    Human infants as young as 14 to 18 months of age help others attain their goals, for example, by helping them to fetch out-of-reach objects or opening cabinets for them. …
  • Chimpanzee Social Intelligence: Selfishness, Altruism, and the Mother-Infant Bond
    S Hirata. Primates 50 (1), 3-11. PMID 19137389. - Review
    To better understand the human mind from an evolutionary perspective, a great deal of research has focused on the closest living relative of humans, the chimpanzee, using …
See all similar articles

Cited by 31 PubMed Central articles

See all "Cited by" articles


    1. {'text': '', 'index': 1, 'ids': [{'type': 'DOI', 'value': '10.1126/science.7466396', 'is_inner': False, 'url': ''}, {'type': 'PubMed', 'value': '7466396', 'is_inner': True, 'url': ''}]}
    2. Axelrod R, Hamilton WD (1981) The evolution of cooperation. Science 211:1390–1396 - PubMed
    1. {'text': '', 'index': 1, 'ids': [{'type': 'DOI', 'value': '10.1098/rspb.1999.0687', 'is_inner': False, 'url': ''}]}
    2. Barrett L, Henzi SP, Weingrill T, Lycett JE, Hill RA (1999) Market forces predict grooming reciprocity in female baboons. Proc R Soc Lond Ser B 266:665–670
    1. {'text': '', 'index': 1, 'ids': [{'type': 'DOI', 'value': '10.1016/j.beproc.2006.07.005', 'is_inner': False, 'url': ''}, {'type': 'PubMed', 'value': '16978800', 'is_inner': True, 'url': ''}]}
    2. Beran MJ, Evans TA (2006) Maintenance of delay of gratification by four chimpanzees (Pan troglodytes): the effects of delayed reward visibility, experimenter presence, and extended delay intervals. Behav Process 73:315–324 - PubMed
    1. {'text': '', 'index': 1, 'ids': [{'type': 'DOI', 'value': '10.1002/ajp.20261', 'is_inner': False, 'url': ''}, {'type': 'PubMed', 'value': '16786518', 'is_inner': True, 'url': ''}]}
    2. Brosnan SF, Freeman C, de Waal FBM (2006) Partner’s behavior, not reward distribution, determines success in an unequal cooperative task in capuchin monkeys. Am J Primatol 68:713–724 - PubMed
    1. {'text': '', 'index': 1, 'ids': [{'type': 'DOI', 'value': '10.1371/journal.pone.0001518', 'is_inner': False, 'url': ''}, {'type': 'PMC', 'value': 'PMC2204064', 'is_inner': False, 'url': ''}, {'type': 'PubMed', 'value': '18231604', 'is_inner': True, 'url': ''}]}
    2. Brosnan SF, Grady M, Lambeth S, Schapiro S, Beran MJ (2008) Chimpanzee autarky. PLoS ONE 3(1):e1518 - PMC - PubMed

Publication types