Signalled Reinforcement and Dimensional Stimulus Control

For four pigeons reinforcement was signalled in one component of a multiple variable-interval 1-min variable-interval 1-min schedule, and two pigeons were trained on a multiple variable-interval 1-min extinction schedule. Following training each bird was given a resistance-to-extinction generalization test, followed by an additional training session, and a final resistance-to-reinforcement generalization test. Test stimuli were combined with presence or absence of the signal. Generalization tests uniformly showed differential dimensional stimulus control in the presence and absence of the signal for three of the four signalled-reinforcement subjects. However, excitatory dimension stimulus control was obtained for the one signalled-reinforcement bird that did not respond differentially during training. Similarly, nondifferential, flat, or inhibitory gradients were obtained for the two extinction subjects. These data support an analysis of signalled reinforcement as a conditional discrimination.