Krageloh, C. U., & Davison, M. (2003).
Concurrent-schedule performance in transition: Changeover delays and signaled reinforcer ratios.
Journal of the Experimental Analysis of Behavior,
79, 87-109.
Six pigeons were trained in experimental sessions that arranged
six or seven components with various concurrent-schedule
reinforcer ratios associated with each. The order of the
components was determined randomly without replacement.
Components lasted until the pigeons had received 10 reinforcers,
and were separated by 10-s blackout periods. The component
reinforcer ratios arranged in most conditions were 27:1, 9:1,
3:1, 1:1, 1:3, 1:9 and 1:27; in others, there were only six
components, three of 27:1 and three of 1:27. In some conditions,
each reinforcement ratio was signaled by a different red - yellow
flash frequency, with the frequency perfectly correlated with the
reinforcer ratio. Additionally, a changeover delay was arranged
in some conditions, and no changeover delay in others. When
component reinforcer ratios were signaled, sensitivity to
reinforcement values increased from around 0.40 before the first
reinforcer in a component to around 0.80 before the 10th
reinforcer. When reinforcer ratios were not signaled,
sensitivities typically increased from zero to around 0.40.
Sensitivity to reinforcement was around 0.20 lower in
no-change-over-delay conditions than in change-over-delay
conditions, but increased in the former after exposure to
changeover delays. Local analyses showed that preference was
extreme towards the reinforced alternative for the first 25 s
after reinforcement in changeover-delay conditions regardless of
whether components were signaled or not. In no-changeover-delay
conditions, preference following reinforcers was either absent,
or, following exposure to changeover delays, small. Reinforcers
have both local and long-term effects on preference. The former,
but not the latter, is strongly affected by the presence of a
changeover delay. Stimulus control may be more closely associated
with longer-term, more molar, reinforcer effects.
Key words: concurrent schedules, choice, transition,
generalized matching, stimulus control, key peck, pigeons, krageloh