Any reward will do: Effects of a reverse-reward contingency on size preference with pet dogs (Canis lupus familiaris)

The reverse-reward contingency (RRC) task involves presenting subjects with a choice between one plate containing a large amount of food and a second plate containing a small amount of food. Subjects are then required to select the smaller of the two options in order to receive the larger-magnitude reward. The RRC task is a commonly used paradigm for assessing complex cognition, such as inhibitory control, in subjects. To date, the RRC task has not been tested with pet dogs as subjects, and it may provide insights to their ability to perceive quantities of differing magnitudes. Nine dogs were tested in an RRC task involving three conditions. In Condition 1, plates of food were presented, and the dogs were allowed to consume their choice. In Condition 2, plates with different-sized symbols resembling the quantities of food in Condition 1 were presented, and dogs received food quantities of the same size as their choice (e.g., a larger-magnitude reward for selecting the plate with the larger shape). In Condition 3, the same plates were presented, but dogs received a reverse-sized quantity of food, relative to their choice (e.g., a smaller-magnitude reward for selecting the plate with the larger shape). A novel addition here to the traditional RRC task was the inclusion of a third, empty (control) plate that was present throughout all conditions, and no programmed consequences were provided when that plate was selected. Our results were consistent with the previous RRC literature: All dogs developed and maintained a preference for the larger stimulus option across conditions. The use of symbolic representations did not ameliorate performance on the RRC task. Applied implications are discussed.