Johnstone, V., & Alsop, B. (1999). Stimulus presentation ratios and the outcomes for correct responses in signal-detection procedures. Journal of the Experimental Analysis of Behavior, 72, 1-20.

Three pigeons were trained to discriminate between two line orientations (S1 and S2). A left-key peck was correct when S1 was presented, and a right key-peck was correct when S2 was presented. In all procedures, correct responses were occasionally reinforced with food paired with the presentation of the magazine light. Incorrect responses produced a blackout. Six detection procedures were used. In the first, the signal presentation ratio was varied across conditions and the reinforcer ratio was allowed to covary. In the second, the signal presentation ratio was held constant at 1:1 and the reinforcer ratio varied across conditions. In the third, the signal presentation ratio was varied across conditions and the reinforcer ratio was held constant at 1:1. In these three procedures, correct responses that were not scheduled for reinforcement were followed by blackout. The remaining three procedures repeated those described above with one procedural change: Nonreinforced but correct trials were followed by the presentation of the magazine light. Birds showed systematic preferences for the key associated with the stimulus presented or reinforced most often. There was no change in the birds' performance over changes in the feedback for nonreinforced but correct responses.

Key words: signal detection, response bias, discriminability, stimulus presentation ratio, outcomes, key peck, pigeons