Previous studies have shown an induction phenomenon, i.e. a considerable decrement in behavior variability and facilitation of a running response, of the rat when reinforcement was presented after or between nonreinforced trials in the semi-circular maze. The purpose of the present experiment was to determine the amount of induction found when the reinforced test trials in the semi-circular maze were given immediately after an extinction which was conducted in the runway or the jumping apparatus.
Forty-eight hungry white rats were equally devised into two groups (Group R and J). After exploration and pretraining,
Ss in the former group were given 10 reinforced trials per day in the straight runway apparatus, and, one hr. later, they were also given 20 reinforced trials per day in the semi-circular maze.
Ss in the latter group were similarly treated except that they received the trials in the jumping apparatus followed by the semi-circular maze. The same procedure continued for 4 days. On the following day, half of the
Ss in each group were given 50 extinction trials in the straight runway (Group R-E) or in the jumping apparatus (Group J-E), respectively, and then, immediately after that, they were run 20 reinforced test trials in the semi-circular maze. The other half of the
Ss in each group did not receive the extinction trials; they were given the reinforced test trials in the semi-circular maze without extinction either in the runway (Group R-C) or in the jumping apparatus (Group J-C). These test sessions repeated for 3 days. On the following day, all
Ss were given 60 extinction trials in the semi-circular maze, and immediately afterward 20 reinforced test trials were given in the same maze.
The results obtained during the test trials in the semi-circular maze were:
(1) When compared with the non-extinction groups (Group R-C and J-C), induction, i.e. the decrement of behavior variability (in three measures) and facilitation of running response, were found in the two extinction groups (Group R-E and J-E) in which their responses were extinguished only in the apparatus other than the semi-circular maze. The analysis of variance of the data showed that extinction produced significant differences in three behavior variability measures in Group R and Group J, and in the running time in the Group R.
(2) When these data, however, were compared with those of the previous study in which almost the same number of nonreinforced trials were given in the semi-circular maze, significantly less amount of induction was found in the present experiment.
(3) A significant interaction between amount of induction and maze difference (runway or jumping apparatus) was found. That is, more induction was obtained after extinction in the straight runway than in the jumping apparatus.
(4) The extinction in the same semi-circular maze produced significantly more induction than those obtained after extinction in the other two mazes. Results in (2), (3) and (4) showed that the greater the similarity of the test to the extinction situation, the greater the induction.
From the above results, induction seems to be closely dependent upon some internal state produced by the nonreinforcement whether nonreinforcement was administered in the same maze or not. Secondly, amount of induction was also related to the similarity between the test and the extinction situation.
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