Jones, B. M., & Davison, M. (1998).
Reporting contingencies of reinforcement in concurrent schedules.
Journal of the Experimental Analysis of Behavior,
69, 161-183.
Five pigeons were trained on concurrent variable-interval
schedules in which two intensities of yellow light served as
discriminative stimuli in a switching-key procedure. A
conditional discrimination involving a simultaneous choice
between red and green keys followed every reinforcer obtained
from both alternatives. A response to the red side key was
occasionally reinforced if the prior reinforcer had been obtained
from the bright alternative, and a response to the green side key
was occasionally reinforced if the prior reinforcer had been
obtained from the dim alternative. Measures of the
discriminability between the concurrent-schedule alternatives
were obtained by varying the reinforcer ratio for correct red and
correct green responses across conditions in two parts. Part 1
arranged equal rates of reinforcement in the concurrent schedule,
and Part 2 provided a 9:1 concurrent-schedule reinforcer ratio.
Part 3 arranged a 1:9 reinforcer ratio in the conditional
discrimination, and the concurrent-schedule reinforcer ratio was
varied across conditions. Varying the conditional discrimination
reinforcer ratio did not affect response allocation in the
concurrent schedule, but varying the concurrent-schedule
reinforcer ratio did affect conditional discrimination
performance. These effects were incompatible with a
contingency-discriminability model of concurrent-schedule
performance (Davison & Jenkins, 1985), which implies a
constant discriminability parameter that is independent of the
obtained reinforcer ratio. However, a more detailed analysis of
conditional discrimination performance showed that the
discriminability between the concurrent-schedule alternatives
decreased with time since changing over to an alternative. This
effect, combined with aspects of the temporal distribution of
reinforcers obtained in the concurrent schedules, qualitatively
predicted the molar results and identified the conditions that
operate whenever contingency discriminability remains constant.
Key words: choice, discriminability, concurrent schedules,
conditional discrimination, key peck, pigeons