Use of progressive fixed-ratio procedures in the assessment of intracranial reinforcement.

E and his team worked with rats that had tiny wires in their brains. When the rat pressed a lever, it got a mild electric pulse to a pleasure center.

Instead of paying every press, the scientists made the price go up. First press gave one pulse, then two presses, then four, and so on. This is called a progressive fixed-ratio schedule.

The higher the price, the less the rats pressed. The curve was smooth and orderly. Stronger current made the rats press more at every price.

The method gave cleaner data than the old way of paying every single press. It showed a clear dose-response line for brain stimulation.

Capriotti et al. (2017) tried the same idea with kids who have tics. They compared a fixed DRO schedule with a progressive DRO schedule. Both cut tics the same amount, but the kids liked the fixed version better.

Iannaccone et al. (2021) moved the idea to human adults. They used progressive delays instead of progressive ratios. DRA with growing delays worked better than DRO with growing delays.

Hearst (1960) used plain fixed-ratio baselines to test amphetamines in rats. The 1968 paper keeps the FR base but adds the climbing-ratio twist to map brain reward.

If you need to find how strong a reinforcer is, make the cost rise. The progressive ratio gives you a single break-point number you can compare across clients or sessions. Try it next time you assess whether a new token, snack, or game really has muscle. Start with one response, then two, four, eight, and watch where the client stops. That break point tells you the true value of the reward.