Motivation in concurrent variable-interval schedules with food and water reinforcers.

Researchers set up two levers. Pressing one lever sometimes gave food. Pressing the other sometimes gave water. The schedule was variable-interval for both.

Before sessions they let animals eat or drink their fill. They watched which lever the animals chose after each pre-load.

After free food, animals switched to the water lever. After free water, they switched to the food lever. When both were given, the shifts added together.

One full reinforcer pushed behavior toward the other reinforcer. Satiation drove choice in the opposite direction.

Wallander et al. (1983) repeated the food-load test but kept animals at 80% body weight. Matching to reinforcer rate only held at higher weights. The 1974 effect is stronger after acute pre-feeding than after chronic weight loss.

Rapport et al. (1996) kept the same two-lever setup and showed that exponential timing makes animals switch more sharply than arithmetic timing. The satiation effect is schedule-shape dependent.

Leslie (1981) zoomed in on single VI schedules and found local response rate tracks local reinforcement probability. The 1974 shifts are the macro version of these micro tracking rules.

If you run concurrent reinforcement programs, pre-session snacks can swing client preference. Offer water or a break from edible reinforcers to keep both responses active. Watch for satiation during long sessions; rotate reinforcers or adjust access timing to maintain balanced responding.