EFFECTS OF VARIABLE-INTERVAL VALUE AND AMOUNT OF TRAINING ON STIMULUS-GENERALIZATION

In Experiment 1 pigeons pecked a key that was illuminated with a 501-n m light and obtained food by doing so according to a variable-interval (VI) schedule of reinforcement, the mean value of which differed acro ss groups: either 30 s, 120 s, or 240 s. The pigeons in all three grou ps were trained for 10 50-min sessions. Generalization testing was con ducted in extinction with different wavelengths of light. Absolute and relative generalization gradients were similar in shape for the three groups. Experiment 2 was a systematic replication of Experiment 1 usi ng line orientation as the stimulus dimension and a mean VI value of e ither 30 s or 240 s. Again, gradients of generalization were similar f or the two groups. In Experiment 3 pigeons pecked a key that was illum inated with a 501-nm light and obtained food reinforcers according to either a VI 30-s or a 240-s schedule. Training continued until respons e rates stabilized (>30 sessions). For subjects trained with the 30-s schedule, generalization gradients were virtually identical regardless of whether training was for 10 sessions (Experiment 1) or until respo nse rates stabilized. For subjects trained with the VI 240-s schedule, absolute generalization gradients for subjects trained to stability w ere displaced upward relative to gradients for subjects trained for on ly 10 sessions (Experiment 1), and relative generalization gradients w ere slightly flatter. These results indicate that the shape of a gener alization gradient does not necessarily depend on the rate of reinforc ement during 10-session single-stimulus training but that the effects of prolonged training on stimulus generalization may be schedule depen dent.