The absence of reward induces inequity aversion in dogs

The absence of reward inducesinequity aversion in dogs FriederikeRange, Lisa Horn, ZsóﬁaViranyi, & Ludwig Huber Presentation by Christy Samuels

Why test dogs on inequality aversion? • It seems likely that a part of the evolution of cooperation is the ability to compare others’ efforts and gains to one’s own • Non-human primates have been shown to abstain from cooperative problem-solving tasks if they observe a conspecific receive a higher-value reward for the same effort • This inequity aversion hadn’t been studied in non-primates

Previous studies with primates • http://www.nature.com/nature/journal/v425/n6955/full/nature01963.html • Capuchin monkeys exchanged a token with an experimenter for a food reward • The monkeys refused to participate if they saw a conspecific get a higher-value reward for the same effort • This effort effect could not be replicated as decisively in another study, but it seems capuchin monkeys have some sensitivity to unequal reward distribution

Method • 29 dogs in the first experiment, 14 in the second • For each session, dogs were paired and asked to “give paw” • This was repeated for 30 trials, or until the subject refused to work • The experimenter did not communicate with the dogs except to give the command “paw”, and both high-value (sausage) and low-value (dark bread) rewards were present in all sessions

Test conditions

Results • The subjects stopped giving their paw sooner when their partner received a reward and they did not

Results cont. • The subjects also needed to be prompted more and showed more signs of stress in the reward inequity (RI) condition than in the baseline or asocial control

Experiment 2 • To control for the presence of the partner, the researchers did a follow-up study • They repeated the reward inequity (RI) condition and added a social control (SC) where neither dog received a reward

Discussion • These experiments provide evidence for sensitivity toward an unequal reward distribution in a cooperative, non-primate species • The dogs refused to “give paw” earlier, hesitated longer, and showed more signs of stress when their partner received a reward and they did not • The dogs did not act differently when their partner received a higher-value reward

The absence of reward induces inequity aversion in dogs