Abstract
The purposes of the present study were to examine the effects of nonreinforced preexposure to the discriminative stimuli on the discrimination learning in goldfish (Exp. I), and to investigate the relation of length of daily preexposure time to preexposure effects (Exp. II).
The experiment consisted of adaptation and pretraining period (5 days), nonreinforced preexposure period (10 days), and simultaneous discrimination learning period. In Exp. I, 16 goldfish were divided into two groups and preexposed for 22 hours a day in preexposure period : one group (N=8) was preexposed to the discriminative stimuli (Fig. 2, A) while the other group (N=8) was preexposed to the irrelevant stimuli to later discrimination (Fig. 2, B). In Exp. II, 32 goldfish were divided into three groups and preexposed to the discriminative stimuli in preexposure period : one group (N=10) was preexposed for 22 hours a day, the second group (N=12) was preexposed for 30 minutes a day, and the third group (N=10) as a control was not preexposed.
The main results were as follows : (1) the groups preexposed to the discriminative stimuli were habituated to those stimuli (Table 1, 2); (2) the groups preexposed to the discriminative stimuli were inferior on the discrimination to the groups not preexposed to the discriminative stimuli (Table 1, 2); (3) the group preexposed to the irrelevant stimuli was superior in performance of discrimination to the group preexposed to the discriminative stimuli and to the control group (Table 1, 2); and (4) the longer the daily preexposure time was, the stronger the preexposure effects (habituation to the discriminative stimuli and inferiority on discrimination learning) became (Table 2).
