Below is a summary of a study conducted by Dr. Adam Kay‘s Animal Behavior class (BIOL 330) at the University of St. Thomas in April 2013. Students collected data with help from friends and families. Students then wrote blog posts that they submitted as an assignment. Below are excerpts (in quotations) from these posts, with some text (from Adam) to tie things together. A complete list of authors (i.e., students in the class) is at the end of the post. We are grateful to the owners and dogs that participated in the study.
“Imagine a scenario in which you and your sibling are paid to walk your family’s dog. That sounds great at first. But then imagine you find out that your sibling is being paid twice as much as you to do the same task. Not fair! How would you respond to such a situation? You might put less effort into doing the chore or maybe even refuse to cooperate altogether because you know you’re not being fairly compensated. This behavior, a resistance to perceived unfairness in social situations, is known as inequity aversion, and its existence is thought to explain some uncooperative behaviors in otherwise cooperative species.”
“Humans show a strong aversion to inequity (Fehr & Schmidt 1999), as do other primates like chimpanzees (Brosnan, Schiff, & de Waal 2005)”, however the prevalence of inequity aversion in non-primates is not yet known. “Crows and ravens have shown remarkable sensitivity to equity in the quality of a reward as well as the effort required to obtain said reward (Wascher & Bugnyar, 2013). In trials where subjects were required to perform a task for a reward after observing a conspecific either acquiring a better-quality reward or obtaining the same reward for performing no task at all, subjects were significantly more unlikely to cooperate in the task than in control experiments where rewards and effort were equal.” “A recent study (Range et al. 2009) suggested that this behavior may also be present in dogs; the study showed that dogs were less likely to perform the energy-costing trick of shaking paws if a dog treat was given to another dog who did not perform a trick than if they were given a treat or if the treat was simply withheld.” “Dogs are inherently social, pack animals. They have been thought to be selected for their cooperativeness through domestication by humans. Over 80% of dog owners think that their pets feel jealousy, which requires that the dogs have some understanding of fairness and equality (Morris, Doe & Godsell, 2008).”
We used social connections to recruit participants for the study. “The experiment consisted of 43 domestic dogs. Experiments asked for the primary dog to shake its paw up to 30 times for each condition. The number of shakes given and number of whines by the primary dog were recorded. We conducted two-way ANOVA tests to analyze the data to find main effects and interactions between the various conditions. “(See here for complete methods)
Number of shakes (Fig. 1) differed significantly in the reward condition (F1, 161=34.30, P<0.0001) but not amongst the social condition (F1, 161= 0.685, P=0.418).” Importantly, “the interaction of grouping and presence of treat did not have an effect on number of shakes (p = 0.2431). “
“These results imply that based on our research, there was no significant inequity aversion by the dogs, but rather just a simple reaction based on if a reward was given for completing a task. These results are contrary to the findings of Range et al. suggesting that dogs do not display inequity aversion behaviors.“
Interestingly, “after removing outliers from the data, we did find a significant interaction (Fig. 2) between reward presence and social grouping (p=0.0317)” as predicted by Range et al. 2009. Note however that the interaction is due to more shakes in the social-treat situation, not fewer shakes in the social-no treat condition.
“One reason for [the discrepancy between our results and those of Range et al. (2009)] may be the environment in which testing took place. Range et al. conducted tests either in a lab or in the owner’s home, whereas we conducted tests exclusively in owner’s home. Range et al. also noted that the dogs tested were ‘trained’ to work with their owners daily.” Overall, these results suggest that inequity aversion in dogs may be a relatively unimportant phenomenon that can only be demonstrated in highly structured conditions. Instead, the presence of food may have an overwhelming influence on dog responsiveness to human commands, regardless of the social context.
Authors: Tyler Abrahamson; Ari Althoff; Stephen Buckeye; Farida Ekue-Hettah; Lauren Friess; Heather Gilbert; Alison Inhelder; Andrea Keller; Joseph Lackner; Breann MacFadyen; Jack Massee; Luke Nolby; Caitlynne Owens; Katie Rehs; Leah Richman; Hailey Roberts; Devon Sauerer; Samantha Schwab; Elizabeth Shearer; Anthony Spano; Nick Spielman; Kim Uy; Jason Yick; Gavin Yseth.