Table 1.

Summary of predictions.

predictionsmodeloutcome
grooming interventions give interveners access to attractive grooming partners
 (1) grooming interventions are more likely when HRG is high-ranking or close to bystander in rank1.1not supported
  (2) grooming interventions are independent of LRG rank1.1not supported
  (3) grooming interventions are more likely when PG has strong affiliative relationship with bystander1.2supported
  (4) grooming intervention likelihood is not affected by affiliative relationship between groomers1.2not supported
  (5) interveners target HRG2not supported
  (6) interveners target PG2not supported
  (7) intervention success independent of affiliative relationships3.2supported
grooming interventions impede grooming with potentially negative consequences for bystander
  (1) grooming interventions are independent of HRG rank1.1supported
  (2) grooming interventions are more likely when LRG is close to bystander in rank1.1supported
  (3) grooming interventions are more likely when PG has strong affiliative relationship with bystander1.2supported
  (4) grooming interventions are more likely if groomers have a weak affiliative relationship1.2supported
  (5) interveners do not target HRG2supported
  (6) interveners do not target PG2supported
  (7) intervention success is independent of affiliative relationships3.2supported
grooming interventions are affected by the social system of the species
  (1) in mangabeys, high-ranking bystanders are more likely to intervene than low-ranking bystanders1.1supported
  (2) in mangabeys, high-ranking interveners are more likely to be successful than low-ranking interveners3.1supported
  (3) in mangabeys, but not chimpanzees, individuals intervene to gain access to high-ranking groomers1.1not supported
  (4) in chimpanzees, but not mangabeys, bystanders intervene more when their affiliative partners are grooming1.2not supported
  (5) in chimpanzees, low- and high-ranking bystanders are equally likely to intervene1.1supported
  (6) in chimpanzees, low- and high-ranking interveners are equally likely to be successful3.1supported