Maintaining performance in searching dogs: Evidence from a rat model that training to detect a second (irrelevant) stimulus can maintain search and detection responding.

Scent-detecting dogs perform a sequence, or chain, of behaviors that, at minimum, includes searching followed by a detection behavior that signals the presence of a target stimulus to the handler. However, when working, dogs often engage in prolonged periods of searching without encountering a target. It is therefore important for trainers to use methods that promote persistent search behavior and target detection accuracy. Laboratory models can provide insights to the important variables that influence search persistence and accuracy. The present experiments examined a rat model of detection dog behavior. Two experiments assessed the use of practice with a single target stimulus to maintain search and detection of another previously-trained target. In Experiment 1, after learning a search→detection chain with two auditory targets, rats received either brief or extended training with only one of the targets before being tested for detection of both targets in extinction. The results suggest that single-target training strengthened the ability of the other target to control the detection behavior. Experiment 2 found that even infrequent target encounters were still effective at maintaining detection behavior to the other trained target. Importantly, the treatment was effective when the target stimuli were from different sensory modalities. Overall, the results support the utility of the rat model of search-dog behavior for evaluating novel training methods. We suggest several useful procedures for enhancing search persistence and accuracy in detection dogs that can be implemented in training protocols.

Increasing the persistence of a heterogeneous behavior chain: Studies of extinction in a rat model of search behavior of working dogs.

Dogs trained to search for contraband perform a chain of behavior in which they first search for a target and then make a separate response that indicates to the trainer that they have found one. The dogs often conduct multiple searches without encountering a target and receiving the reinforcer (i.e., no contraband is present). Understanding extinction (i.e., the decline in work rate when reinforcers are no longer encountered) may assist in training dogs to work in conditions where targets are rare. We therefore trained rats on a search-target behavior chain modeled on the search behavior of working dogs. A discriminative stimulus signaled that a search response (e.g., chain pull) led to a second stimulus that set the occasion for a target response (e.g., lever press) that was reinforced by a food pellet. In Experiment 1 training with longer search durations and intermittent (partial) reinforcement of searching (i.e. some trials had no target present) both led to more persistent search responding in extinction. The loss of search behavior in extinction was primarily dependent on the number of non-reinforced searches rather than time searching without reinforcement. In Experiments 2 and 3, delivery of non-contingent reinforcers during extinction increased search persistence provided they had also been presented during training. Thus, results with rats suggest that the persistence of working dog performance (or chained behavior generally) may be improved by training with partial reinforcement of searching and non-contingent reinforcement during both training and work (extinction).