A comparison of different measures of response strength in the study of stimulus generalization.

In Experiment 1, three pigeons were given variable interval training to peck at a light of 550 mmu and then were tested for stimulus generalization in extinction to several different wavelengths. A gradient was obtained for latency of the first response in each test period, for the number of test periods in which responding occurred, and for the measure of response rate. When the response rate gradient was corrected for differences in initial latency and in number of responded trials, the change was minimal, indicating that the major component of response rate as usually measured is rate of responding having once responded. In Experiment 2, three other pigeons were trained to respond to 550 mmu (for variable interval reinforcement) and not to 570 mmu (extinguished). Analysis of generalization gradients dictated the same conclusion as that reported for generalization following single stimulus training.