Walker, D. J., & Branch, M. N. (1998).
Effects of variable-interval value and amount of training on stimulus generalization.
Journal of the Experimental Analysis of Behavior,
, 139-163.
In Experiment 1 pigeons pecked a key that was illuminated with a
501-nm light and obtained food by doing so according to a
variable-interval (VI) schedule of reinforcement, the mean value
of which differed across groups: either 30 s, 12 s, or 240 s. The
pigeons in all three groups were trained for 10 50-min sessions.
Generalization testing was conducted 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 using line
orientation as the stimulus dimension and a mean VI value of
either 30 s or 240 s. Again, gradients of generalization were
similar for the two groups. In Experiment 3 pigeons pecked a key
that was illuminated with a 501-nm light and obtained food
reinforcers according to either a VI 30-s or a 240-s schedule.
Training continued until response rates stabilized (;mt30
sessions). For subjects triained with the 30-s schedule,
generalization gradients were virtually identical regardless of
whether training was for 10 sessions (Experiment 1) or until
response rates stabilized. For subjects trained with the VI 240-s
schedule, absolute generalization gradients for subjects trained
to stability were displaced upward relative to gradients for
subjects trained for only 10 sessions (Experiment 1), and
relative generalization gradients were slightly flatter. These
results indicate that the shape of a generalization gradient does
not necessarily depend on the rate of reinforcement during
10-session single-stimulus training but that the effects of
prolonged training on stimulus generalization may be schedule
dependent.
Key words: stimulus generalization, generalization gradient,
reinforcement rate, amount of training, variable- interval
schedule, key peck, pigeons