A laboratory model of canine search vigilance decrement, I

Previous studies have found that infrequent targets can reduce dogs' vigilance. The purpose of this study was to develop a laboratory model to evaluate the effects of infrequent targets on dogs' search behavior and performance. Dogs (n = 18) were trained to detect smokeless powder in an automated olfactometer in two distinct rooms ("operational" and "training"). During baseline, the dogs received five daily sessions at a high target odor frequency (90%) in both rooms. Subsequently, the frequency of the target odor was decreased to 10% only in the "operational" room but remained at 90% in the training room. Last, the odor prevalence was returned to 90% in both rooms. All dogs showed a significant decrement in detection performance in the operational room when the target odor frequency was decreased but simultaneusly mantained high performance in the training room. This decrement was largely due to decreases in adequate search behavior. All dogs recovered performance when the odor frequency was increased again to 90%. Trial accuracy was associated with tail position, search score, latency, and duration of environmentally directed behaviors. The data show that low target odor prevalence significantly reduced search behavior and performance and that there are behaviors that can be used by handlers to assess their dog's search state.