Effects of discrete-trial and free-operant procedures on the acquisition and maintenance of successive discrimination in rats.
Rats were trained on a successive discrete-trial discrimination between two tonal stimuli to examine the effects of availability of a lever during intertrial intervals. In the discrete-trial condition, in which a lever was removed from the chamber during intertrial intervals, 10-s trials were initiated by the presentation of both discriminative stimulus and lever. In the free-operant condition, in which a lever was present during both trials and intertrial intervals, 10-s trials were initiated only by the presentation of a discriminative stimulus. Experiment 1 employed 50-s intertrial intervals and demonstrated that discriminative performances were acquired faster and maintained better in the free-operant conditions than in the discrete-trial conditions. Experiment 2 employed 5-s intertrial intervals and showed that poor discriminative performances in the discrete-trial conditions were improved. These results indicate that the presentation of a lever to start a trial can overshadow or mask the control by a discriminative stimulus and thereby obstruct the acquisition and maintenance of discriminative performances. Furthermore, the overshadowing or masking effects are strengthened as a function of the duration of intertrial intervals.
Hachiya
S
S
Osaka City University, Japan.
Ito
M
M
D000818:Animals; D001070:Appetitive Behavior; D001245:Association Learning; D001288:Attention; D003216:Conditioning, Operant; D004193:Discrimination Learning; D008297:Male; D011939:Mental Recall; D010897:Pitch Discrimination; D011597:Psychomotor Performance; D051381:Rats; D011919:Rats, Inbred Strains