The effect of reinforcer delays on the form of the forgetting function.

Madden et al. (2003) worked with pigeons on a delayed matching-to-sample task. Birds saw a color sample, waited 0–16 s, then picked the matching key.

The team changed when food arrived: right after the choice, or 2, 4, or 8 s later. They tracked how quickly memory faded at each food delay.

Longer food delays made the birds forget faster. Early accuracy dropped and the whole forgetting curve became steeper.

Even though the choice delay stayed the same, waiting for food hurt memory more than waiting to choose.

Burgio et al. (1986) saw the same drop when food was late, but they showed the choice delay hurts more than the food delay. Madden et al. (2003) add that once the choice is fixed, food delay still erodes memory.

Rider et al. (1984) first drew the hyperbolic forgetting curve. The new data keep that shape but tilt it further, proving reinforcer timing bends the curve itself.

Eisenmajer et al. (1998) found food timing matters more than choice timing. Madden et al. (2003) agree and spell out the cost: steeper forgetting, not just lower accuracy.

For BCBAs this means delivery speed counts twice: it keeps motivation high and protects the memory you just built. When teaching new discriminations, deliver praise, tokens, or snacks right after the response. Even a few seconds of extra wait can flatten the whole learning curve for that trial and the next.