Delay of reinforcement in instrumental discrimination learning of rats

Assigned 4 groups of 8 male albino rats each to a 2-choice discrimination task. Ss were reinforced for pressing 1 lever in the presence of 1 auditory stimulus and for pressing an alternative lever in the presence of a 2nd auditory stimulus. Acquisition of the discrimination was retarded when reinforcement was delayed for all or a random half of the correct responses in the presence of each stimulus. However, performance was facilitated when reinforcement was delayed for all of the correct responses in the presence of 1 stimulus but not the other. Results are interpreted in terms of both classical and operant mediational processes