EFFECTS OF A DRL CONTINGENCY ADDED TO A FIXED-INTERVAL REINFORCEMENT SCHEDULE.

The team added a DRL rule on top of a 30-second fixed-interval schedule. A DRL rule means the next response has to wait a set time or it does not count. They watched how this extra rule changed the speed of responding.

They ran the test in a lab with single-case methods. The goal was to see if DRL could fine-tune response rate without killing the basic FI pattern.

Adding the DRL rule pushed response rates down in a smooth, curved way. The longer the DRL requirement, the slower the responses. After each reinforcer, the next pause was extra sharp. After non-reinforced responses, timing was looser.

MOLLIVER (1963) had already shown that a pure DRL schedule can slow down single words. The new study goes further: it proves DRL still works when it is stacked on top of an FI schedule.

SHETTLEWORTCHARNEY et al. (1965) used both FI and DRL with brain-stimulation reward. They found schedule control looks the same no matter what the reinforcer is. The 1964 paper matches that pattern, but shows the control can come from two schedules acting together.

Thomas (1968) later broke FI responding into tiny sequential parts. The smooth rate drops seen here gave him the clean baseline he needed for that deeper cut.

If you need to cut rapid, stereotypic responses, you can layer a short DRL window onto any existing FI program. You keep the FI payoff, but the client learns to wait a beat. Try a 3-second DRL on a 30-second FI for mouthing or repetitive button pushes. Watch the inter-response times stretch; reinforce the first response after the window passes. Fade the DRL requirement once the pace feels safe.