[A study of relation between phrasing and intertrial interval in reinforcement pattern learning in rats].

Abstract

Effects of the temporal interval on reinforcement pattern learning were investigated in four experiments using a runway. The reinforced trial was always the first trial for R5N sequence (Experiments 1a and 1b), and the fourth trial for 3NR2N sequence (Experiments 2a and 2b). Group S-ITI received the given sequence at 30-s ITI, Group L-INT received the same procedure as Group S-ITI except for a 30-min ITI inserted between Trials 3 and 4 (Experiments 1a and 2a). Group L-ITI received at 30-min ITI, Group S-INT did as Group L-ITI except for the ITI between Trials 3 and 4 was 30 seconds (Experiments 1b and 2b). It was found that the running speed on each of Trials 1 and 4 was faster than any other trials under R5N and 3NR2N sequences for Group L-INT. That is, the running pattern for Trials 1-3 was similar to that for Trials 4-6. On the other hand, the running speed on Trial 4 under R5N sequence and that on Trial 1 under 3NR2N sequence did not increase for Group S-INT. These results suggest that a longer or shorter ITI plays the roles of both phrasing cue and discriminative stimulus. For Group S-ITI and Group L-ITI, there was little evidence that sequences were phrased. Therefore, when trials are separated by equal ITIs, neither 30-s ITI nor 30-min ITI becomes a phrasing cue.