Davison, M., & Baum, W. M. (2002).
Choice in a variable environment: Effects of blackout duration and extinction between components.
Journal of the Experimental Analysis of Behavior,
77, 65-89.
Pigeons were trained in a procedure in which sessions included
seven four- or 10-reinforcer components, each providing a
different reinforcer ratio that ranged from 27:1 to 1:27. The
components were arranged in random order, and no signals
differentiated the component reinforcer ratios. Each condition
lasted 50 sessions, and the data from the last 35 sessions were
analyzed. Previous results using 10-s blackouts between
components showed some carryover of preference from one component
to the next, and this effect was investigated in Experiment 1 by
varying blackout duration from 1 s to 120 s. The amount of
carryover decreased monotonically as the blackout duration was
lengthened. Preference also decreased between reinforcers within
components, suggesting that preference change during blackout
might follow the same function as preference change between
reinforcers. Experiment 2 was designed to measure preference
change between components more directly and to relate this to
preference change during blackout. In two conditions a 60-s
blackout occurred between components, and in two other conditions
a 60-s period of unsignaled extinction occurred between
components. Preference during the extinction period progressively
fell toward indifference, and the level of preference following
extinction was much the same as that following blackout. Although
these results are consistent with Davison and Baum's (2000)
theory of the effects of reinforcers on local preference, other
findings suggest that theory is incomplete: After a sequence of
reinforcers from one alternative, some residual preference
remained after 60 s of extinction or blackout, indicating the
possibility of an additional longer term accumulation of
reinforcer effects than originally suggested.
Key words: concurrent schedules, choice, carryover, blackout,
extinction, key peck, pigeons