Mazur, J. E. (1998).
Procrastination by pigeons with fixed-interval response requirements.
Journal of the Experimental Analysis of Behavior,
69, 185-197.
Two experiments studied the phenomenon of procrastination, in
which pigeons chose a larger, more delayed response requirement
over a smaller, more immediate response requirement. The response
requirements were fixed-interval schedules that did not lead to
an immediate food reinforcer, but that interrupted a 55-s period
in which food was delivered at random times. The experiments used
an adjusting-delay procedure in which the delay to the start of
one fixed-interval requirement was varied over trials to estimate
an indifference point -- a delay at which the two alternatives
were chosen about equally often. Experiment 1 found that as the
delay to a shorter fixed-interval requirement was increased, the
adjusting delay to a longer fixed-interval requirement also
increased, and the rate of increase depended on the duration of
the longer fixed-interval requirement. Experiment 2 found a
strong preference for a fixed delay of 10 s to the start of a
fixed-interval requirement compared to a mixed delay of either 0
or 20 s. The results help to distinguish among different
equations that might describe the decreasing effectiveness of a
response requirement with increasing delay, and they suggest that
delayed reinforcers and delayed response requirements have
symmetrical but opposite effects on choice.
Key words: choice, fixed-interval schedules, delay,
procrastination, key peck, pigeons