Independence of stimulus discriminability from absolute rate of reinforcement in a signal-detection procedure.

Rapport et al. (1982) worked with pigeons in a signal-detection box. Birds pecked left or right depending on how long a light stayed on.

The team kept the light cues the same but doubled, then tripled, the grain payoff for correct guesses. They wanted to know if bigger payoffs would make the birds better at telling the durations apart.

Payoff size did not budge the birds’ accuracy. Discriminability stayed flat while reinforcement rate swung from lean to rich.

The result says stimulus properties, not the size of the prize, control how well a subject can see (or hear) the difference.

Two years earlier the same lab wrote Gentry et al. (1980). That paper showed relative payoff shifts response bias but leaves sensitivity untouched. The 1982 study widened the test to absolute rate and found the same independence, forming a clean replication line.

Malouff et al. (1985) then extended the claim to free-operant detection. Even when grain dripped at very different speeds within components, discriminability held steady, strengthening the rule across procedures.

LeBlanc et al. (2003) looks like a contradiction: richer schedules lifted both response rate and discrimination accuracy. The clash fades when you see they tested resistance to disruption, not moment-to-moment sensitivity. Higher rate strengthened maintenance, not the birds’ raw ability to tell stimuli apart.

For BCBAs this splits the ABC you control. Reinforcement rules your client’s willingness to respond (bias), but it will not sharpen blurry stimulus control. If a learner mixes up ‘b’ and ‘d’, raise reinforcement to keep them trying, then turn to stimulus shaping, errorless teaching, or better discrimination training to fix the blur.