Davison, M. & Baum, W.M. (2007).
Local effects of delayed food.
Journal of the Experimental Analysis of Behavior, 87, 241-260.
Five pigeons were trained on a procedure in which seven concurrent variable-interval schedules arranged seven
different food*rate ratios in random sequence in each session. Each of these components lasted for 10
response-produced food deliveries, and components were separated by 10-s blackouts. We varied delays to food
(signaled by blackout) between the two response alternatives in an experiment with three phases: In Phase 1,
the delay on one alternative was 0 s, and the other was varied between 0 and 8 s; in Phase 2, both delays were
equal and were varied from 0 to 4 s; in Phase 3, the two delays summed to 8 s, and each was varied from 1 to
7 s. The results showed that increasing delay affected local choice, measured by a pulse in preference, in the
same way as decreasing magnitude, but we found also that increasing the delay at the other alternative increased
local preference. This result casts doubt on the traditional view that a reinforcer strengthens a response
depending only on the reinforcer’s value discounted by any response–reinforcer delay. The results suggest that
food guides, rather than strengthens, behavior.
Key words: choice, delayed food, generalized matching, contingency discriminability, preference pulses, key peck, pigeons