Jacobs, E. A., & Hackenberg, T. D. (1996).
Humans' choices in situations of time-based diminishing returns: Effects of fixed-interval duration and progressive-interval step size.
Journal of the Experimental Analysis of Behavior,
65, 5-19.
Four adult humans made repeated choices between two time-based
schedules of points exchangeable for money: a fixed-interval
schedule and a progressive interval schedule that began at 0 s
and increased in fixed increments following each point d elivered
by that schedule. Under reset conditions, selection of the fixed
schedule not only produced a point but also reset the progressive
interval to 0 s. Reset conditions alternated with no-reset
conditions, in which the progressive-interval duration was
independent of fixed-interval choices. Fixed-interval duration
and progressive-interval step size were varied independently
across conditions. Subjects were exposed to all step sizes in
ascending order at a given fixed-interval value before the value
was changed. Switching from the progressive-interval schedule to
the fixed-interval schedule was systematically related to
fixed-interval duration, particularly under no-reset conditions.
Switching occurred more frequently and earlier in the
progressive-schedule sequence under reset conditions than under
no-reset conditions. Overall, the switching patterns conformed
closely to predictions of an optimization account based upon
maximization of overall reinforcement density, and did not appear
to depend on schedule-controlled response patterns or on verbal
descriptions of the contingencies.
Key words: choice, optimization, progressive-interval schedules,
fixed-intervalschedules, key press, adult humans