The interaction of stimulus and reinforcer control in complex temporal discrimination.

Rutter et al. (1987) worked with pigeons in a temporal bisection task. Birds pecked left or right after seeing a short or long light. The team changed which duration paid off more often. They wanted to know if the payoff shift changed how well birds told time or just biased their choices.

When short durations paid more, birds pecked the short side more often. When long durations paid more, they pecked the long side more often. Yet the birds' true ability to tell the two durations apart stayed the same. Only their bias moved, not their sensitivity.

Pinheiro de Carvalho et al. (2012) later showed pigeons learn faster when each duration maps to one key, not when durations share keys. This builds on Rutter et al. (1987) by proving absolute stimulus control, not relational rules, drives temporal choices.

McGonigle et al. (1982) found brief immediate stimuli can override delayed rewards. Together with Rutter et al. (1987), the two studies show that cues tied to reinforcers bias choices without changing the animal's underlying discrimination.

Coe et al. (1997) varied reinforcer ratios for frequency, not duration, and saw the same pattern: bias shifts, sensitivity stays flat. The same mechanism appears across stimulus dimensions.

You can shift a client's preference without teaching a new skill. Arrange richer reinforcement for the response you want now, even if the learner can already tell the stimuli apart. Watch for bias changes in your data, not just accuracy jumps.