What if the reward is not as yummy? Study of the effects of successive negative contrast in domestic dogs in two different tasks

Successive negative contrast (SNC) occurs when there is a reduction in the quantity or quality of a reward that is expected according to the presence of contextual cues. This induces an emotional response of "frustration" that is similar to stress. While this phenomenon has been observed in several mammal species, findings in domestic dogs have been inconsistent, although this issue has strong relevance in dog training. The aim of this study was to assess the effects of SNC in two responses that had already been studied in this species, but with an increase in the methodological rigor and variations in the experimental conditions to examine the generalizability of the phenomenon. To this end, experimental dogs experienced a preshift phase in which they received a high-value reward (liver), followed by a postshift phase in which they obtained a low-value reward (dry dog food), and then a reshift phase in which the high-value reward was available again. Control dogs received dry food in all phases. The results show a contrast effect on the behavior of following human pointing to obtain food (study 1). On the contrary, there were no differences in problem-solving behavior after the de- and re-evaluation of the reward during a nonsocial task (study 2). The results support that SNC is not a consistent phenomenon in pet dogs. It is possible that certain characteristics of dogs such as the great availability of high-value rewards in their daily lives could attenuate the effects of a reduction in incentive value.