BRAIN-STIMULATION INTENSITY, RATE OF SELF-STIMULATION, AND REINFORCEMENT STRENGTH: AN ANALYSIS THROUGH CHAINING.

The team built a two-link chain. First link: wait an average of 30 s, then press a lever. Second link: press five times and the brain gets a tiny electric pulse.

They slowly turned up the pulse strength. At each level they counted how fast the animal worked for the pulse alone and how fast it worked inside the chain.

Raw self-stimulation rate peaked at one intensity, then fell. But the chained response kept climbing.

The chain showed stronger reinforcement even after the pulse that felt “best” had passed. Simple rate had hidden the true strength.

Baum (2025) later explained why. Ratio schedules shrink the unit of work, so lean pay breaks them. Interval schedules keep the unit big, letting chains hold steady.

Benway et al. (2024) moved the same chaining logic to speech therapy. Kids practiced /ɹ/ steps online and the skill spread to new words, showing the 1964 rule works outside the lab.

Jones et al. (2024) found interval schedules make cocaine seeking hard to punish. Their result echoes the 1964 finding: interval timing builds tough, persistent behavior.

If you test reinforcer strength only with free-access or simple ratio probes, you may quit too early. Run a short chain or interval schedule. The extra steps can reveal hidden power in a token, game, or break that looks weak on rate alone.