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

Abstract

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).

How effective are trained dogs at alerting their owners to changes in blood glycaemic levels?: Variations in performance of glycaemia alert dogs

“…This highlights the importance of ongoing training in maintaining a well-functioning working animal (e.g. [19, 20]) and suggests the importance of appropriate selection and training of clients, as well as dogs.…”

Factors that influence the persistence and relapse of discriminated behavior chains

“…A long tradition of research on resistance to extinction of simple Pavlovian and instrumental responses suggests that training that involves nonreinforcement will translate to greater persistence during extinction (Capaldi, 1966, 1994). Likewise, training that increased the number of nonreinforced procurement responses led to slower extinction of procurement (Thrailkill, Kacelnik, et al, 2016). Another way to increase generalization is to continue to present stimuli from training during extinction.…”

“…The results (Figure 3b) clearly suggest that extinction of S1R1 was slower in the group tested with noncontingent pellets (P) than the group tested without (NP). It is notable that in another experiment we found that introducing noncontingent reinforcers for the first time during S1R1 extinction reduced S1R1 responding, presumably by creating generalization decrement (Thrailkill et al, 2016, Experiment 2). Therefore, presenting the noncontingent pellets during training and delivering them in the ITI were each important for enhancing the persistence of S1R1 in extinction.…”

“…Thrailkill, Kacelnik, Porritt, and Bouton (2016) therefore studied the effects of partial reinforcement on the persistence of R1 during extinction after it was trained in our discriminated heterogeneous chain. Training proceeded with a method that was similar to that illustrated in Figure 1.…”

“…That is, a reinforcer that follows a response often precedes the reinforcement of a subsequent response. Therefore, we studied whether presenting the reinforcer noncontingently in extinction would likewise slow down the extinction of chained responding (Thrailkill et al, 2016, Experiment 3). Two groups of rats learned the S1R1-S2R2-O chain under conditions in which each group also received two noncontingent deliveries of the food pellet reinforcer during the last 20 s of the ITI.…”