Contiguity of briefly presented stimuli with food reinforcement.

Pigeons pecked a key on a fixed-interval schedule. A brief light flashed right before food arrived.

The team varied how long the light stayed on. They watched how fast the birds pecked.

Shorter light-to-food gaps made the birds peck faster. The response curve looked like a ski slope—slow start, fast finish.

Even a tiny flash worked if it touched the food moment.

Barnard et al. (1977) later showed the same rule in autoshaping. If the response-to-food gap grew past four seconds, pecking stopped.

Catania et al. (2015) counted every millisecond and drew the delay curve. Their numbers now let us predict exactly how much a delay will weaken behavior.

Storch et al. (2012) seems to clash. They saw toy play drop when food itself was the brief cue. The difference is cue function: a neutral light helps, but food-as-a-cue triggers competing eating.

Keep reinforcers close in time. Use a quick praise, token, or beep that lands right before the edible or activity. If you must wait, fill the gap with neutral tasks, not food cues, so you don’t accidentally strengthen the wrong response.