Mazur, J. E. (1996).
Choice with certain and uncertain reinforcers in an adjusting-delay procedure.
Journal of the Experimental Analysis of Behavior,
66, 63-73.
A discrete-trials adjusting-delay procedure was used to
investigate the conditions under which pigeons might show a
preference for partial reinforcement over 100% reinforcement, an
effect reported in a number of previous experiments. A peck on a
red key always led to a delay with red houselights and then food.
In each condition, the duration of the red-houselight delay was
adjusted to estimate an indifference point. In 100% reinforcement
conditions, a peck on a green key always led to a delay with
green houselights and then food. In partial-reinforcement
conditions, a peck on the green key led either to the green
houselights and food or to white houselights and no food. In some
phases of the experiment, statistically significant preference
for partial reinforcement over 100% reinforcement was found, but
this effect was observed in only about half of the pigeons. The
effect was largely eliminated when variability in the delay
stimulus colors was equated for 50% reinforcement conditions and
100% reinforcement conditions. Idiosyncratic preferences for
certain colors or for stimulus variability may be at least
partially responsible for the effect.
Key words: reinforcement probability, reinforcement delay,
conditioned reinforcers, choice, key peck, pigeons