NOTE OF CHANGES IN RESPONSE LATENCY FOLLOWING DISCRIMINATION TRAINING IN THE MONKEY.

Two monkeys learned a simple discrimination task. A light came on. If it was the "correct" color, the monkeys had to let go of a key fast to earn food.

The researchers then switched which color paid off. They tracked how quickly the monkeys released the key after the light changed.

As soon as the payoff rule flipped, the monkeys' release times dropped. Responses to the new "correct" color became both faster and less variable.

Reinforcement did not just make the response more likely. It also sharpened the speed and steadiness of the response itself.

Fox et al. (2001) later showed the same pattern in rats. A single hidden factor—response strength—links speed, probability, and how long the animal keeps trying.

Staddon et al. (2002) built math models that predict exactly this link. Their equations treat faster latency as one face of stronger reinforcement control.

Fahmie et al. (2013) added a twist. When payoff odds shift, response bias changes right away, but accurate discrimination takes extra trials. The 1964 monkey data fit this: latency moved first, then steady stimulus control followed.

Latency is a cheap, live thermometer for reinforcement control. If a child's correct responses speed up after you deliver praise, you know the contingency is biting. If speed stays choppy, the reinforcer or the discrimination may need tweaking. Track release times, button pushes, or sign-on times—any swift motor act—to catch early gains or losses in learning.