Response cost and time-place discrimination by rats in maze tasks

Abstract

Time-place discrimination has been shown reliably in several avian and insect species, but only occasionally in rats and fish. In the present experiments, we explored the effects of response cost on time-place discrimination by rats. In the first experiment, we increased the cost of making a choice and the cost of recovering from a wrong choice in two types of maze, a radial arm and a vertical maze. In the radial arm maze, we found only general place preference, whereas in the vertical maze, we obtained evidence of time-place discrimination. In the second experiment, we found that the proportion of rats showing time-place discrimination increased with the height and, therefore, the response cost of the vertical maze. These results suggest that rats do not automatically store and/or retrieve the time and place of reward events but that response cost is an important trigger for time-place discrimination.

Rats acquire a low-response-cost daily time-place task with differential amounts of food

“…Currently, the best hypothesis to explain why rats learn some TPL tasks but not others is the responsecost hypothesis put forth by Widman et al (2000), but this hypothesis cannot explain the present data or some of the other inconsistencies summarized in the introduction. One thing that is clear, however, is that Gallistel's (1990) tripartite theory needs to be revised.…”

“…Some researchers have found daily TPL in operant response tasks (Carr & Wilkie, 1997a, 1997b, 1999Mistlberger, de Groot, Bossert, & Marchant, 1996;Pizzo & Crystal, 2002), whereas others using very similar paradigms and similar reinforcement schedules have failed to find it (Boulos & Logothetis, 1990;Thorpe et al, 2003;White & Timberlake, 1990). Although Widman et al (2000) believe that response-cost ratios (the relative cost of making an error) are the critical determinants of whether an animal learns a time-place task, it is not clear from a theoretical perspective why this should be the case. Nor does the response-cost theory account for the many inconsistencies in the research findings.…”

“…Neither making the two places more distinctive nor making the two times farther apart during the day significantly increased rats' success rate on the task. Widman et al (2000) discovered that, by increasing the response cost (i.e., effort) in TPL tasks, they increased the probability that the rats would learn the tasks. In a simple radial arm maze similar to those described above (i.e., one arm baited in morning sessions, another arm baited in afternoon sessions), the rats did learn a general place preference (i.e., they learned which two arms were baited), but they did not learn when those places were baited.…”

The influence of temporal spacing on time-place discrimination

“…Thorpe et al also suggested that the reason that their animals did not acquire both components in time-place discrimination relates to the low response cost in their paradigms. Responses cost (i.e., making a choice effortful) promotes time-place discrimination (Widman et al, 2000). Thorpe et al proposed that a high response cost is necessary to encode both time and place.…”

“…Initially, the requirement was an FR1; the ratio was doubled until FR32 or FR64 was reached, thereby increasing the response cost; a high response cost promotes time-place discrimination (Widman, Gordon, & Timberlake, 2000;Widman, Sermania, & Genismore, 2004). Research in our laboratory has suggested that rats show inconsistent performance when the response cost is too high.…”