Preference for mixed versus constant delay of reinforcement.

Pigeons pecked two keys. One key gave food after a fixed delay. The other key gave food after a mixed bag of short and long delays.

The researchers widened the spread of the mixed delays across tests. They wanted to see if more variety made the mixed key even more attractive.

Birds strongly preferred the key with mixed delays. The wider the spread, the stronger the preference.

Even when the average wait was the same, variety won.

Rojahn et al. (1994) later showed the same trick boosts self-control. Pigeons picked the larger, later reward more often when its delay varied instead of staying fixed.

Fine et al. (2005) looked similar but got weaker results. Pigeons only mildly preferred variable-interval over fixed-interval schedules. The difference: the 2005 study used interval schedules, not pure delays, so the payoff rhythm was messier.

Azrin et al. (1967) had already proven that shorter delays win. Cicerone (1976) adds that a mix of delays can beat one steady delay of the same average length.

If a client tires during long, fixed wait times, shake the schedule up. Alternate short and long delays instead of keeping every wait identical.

Try this when teaching tolerance to delayed reinforcement: give the first reinforcer after 2 s, the next after 8 s, then 3 s. The variety itself can keep the learner engaged and may reduce problem behavior that stems from rigid wait expectations.