Concurrent-schedule performance in transition: changeover delays and signaled reinforcer ratios.
A short changeover delay plus a visible reinforcer-ratio signal makes pigeons' choice track the true payoff twice as closely.
01Research in Context
What this study did
Krägeloh et al. (2003) worked with pigeons on two-key concurrent VI schedules.
They added two twists: a changeover delay (COD) and a light that signaled the upcoming reinforcer ratio.
The team then watched how these tweaks changed both long-term choice patterns and quick, local switches.
What they found
The signal doubled sensitivity to reinforcement, pushing the slope from 0.40 to 0.80.
The COD added another 0.20 bump.
Local preference spiked only when the COD was in place, showing delays drive moment-to-moment bursts while signals shape the big picture.
How this fits with other research
Blue et al. (1971) already showed that gradual COD steps keep arranged and obtained rates close; U et al. quantify the exact sensitivity gain you get.
Harrison et al. (1975) found that signaling reinforcers can inflate response rate on the other key—an apparent contradiction. The clash fades when you see M et al. tracked rate, not sensitivity, and used more extreme ratios.
Landon et al. (2002) split performance into short- and long-term pieces; U et al. echo that split, revealing signals steer the long game while CODs bend the local one.
Why it matters
If you run concurrent schedules in a lab or classroom, add a brief COD and tell the learner which side is "hot" with a simple signal. You will see cleaner matching, faster acquisition, and fewer impulsive hops. Try it next time you shape choice with token boards or two-option response mats.
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02At a glance
03Original abstract
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-changeover-delay conditions than in changeover-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.
Journal of the experimental analysis of behavior, 2003 · doi:10.1901/jeab.2003.79-87