“…First, partial delay of reinforcement produced greater resistance to extinction than immediate reinforcement when as few as three acquisition trials were given (Hewlett & Sheldon, 1968) or following training with a 24-hour intertrial interval, 90-day suspension of training, and interpolated immediate-reward training (Donin, Surridge, & Amsel, 1967). Second, Wike and Atwood (1970) and Wike, Mellgren, and Cour (1967) found that when a within-groups design was used, partial delay produced less resistance to extinction than immediate reinforcement.…”