The breakfast effect revisited: Dogs’ scent detection performance before and after a meal

The influence of a recent meal on dogs’ scent-detection performance has not been systematically evaluated. The motivating operations account of motivation suggests that, when hungrier, scent-detection animals will treat a broader range of stimuli as target stimuli, thereby resulting in higher false alarm rates. In the present study, we tested this prediction by evaluating six dogs’ performance in a mixture-detection task using an alternating-treatments design in which they received breakfast prior to the task on some days and after the task on other days. Following training to use an airflow olfactometer, dogs’ indication responses in the presence of the target mixture were reinforced while indications to a non-target chemical or mixture were not reinforced. A key finding from this study was that, as predicted by the motivating operations account, dogs produced significantly more false alarms when they were working before compared to after breakfast. There was no difference in dogs’ mean hit rates between the two conditions, and there were no significant effects on log d (a measure of sensitivity to the target) or log B (a measure of bias). We predicted that dogs would take longer to complete the task in the breakfast compared to the no-breakfast condition, but no significant difference in session duration was found between the two conditions. These findings have important implications for applications involving scent-detection animals. They also raise a variety of additional questions related to the role of motivation and nutrition in scent-detection performance that should be addressed in future research.