Concurrent-chain performance: Effects of absolute and relative terminal-link entry frequency.
Choice locks onto reinforcement rate once the shorter first link lasts at least 32 seconds.
01Research in Context
What this study did
The team used pigeons in a two-key chamber. Each key led to a final food link.
They changed how often each final link could start and how long the first links lasted.
Birds chose between the two keys while the timers ran.
What they found
Choice followed the matching law. Birds picked the key that gave the richer final link.
Sensitivity kept growing until the shorter first link hit 32 seconds. After that, more time did not help.
How this fits with other research
Hattier et al. (2011) kept the 32-second mark and added short shocks. Long first links still cut both preference and staying power. The 1988 peak point still held.
Malone (1976) saw messy bias when final links were unequal. Joyce et al. (1988) shows you can clean the data by pushing first links past 32 seconds.
Steege et al. (1989) swapped pigeons for people the next year. People chased the best overall rate, not the delay cut. Same boxes, new rule.
Why it matters
When you build token boards or chained DRO, set the early wait at or above half a minute. That is the sweet spot where choice becomes stable and you can trust your data. If you run shorter waits, expect noisy preference and extra sessions.
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02At a glance
03Original abstract
Six pigeons were trained in a concurrent-chain procedure with constant variable-interval 6-s variable-interval 12-s terminal links. Five groups of conditions were arranged. Within a group of conditions, the duration of one initial-link schedule was held constant and the duration of the other initial link was varied. The duration of the varied initial link was always longer than, or equal to, the constant initial-link duration. The duration of the shorter initial link was varied across groups of conditions from 5 s to 70 s. The data from each group were well described by the generalized matching law. Sensitivity (a) to the terminal-link entry ratio increased as the shorter initial-link duration increased, but appeared to reach an asymptote at shorter initial-link durations greater than 32 s. Terminal-link bias did not change with changes in shorter initial-link duration for the response-allocation data, but showed a small increase with increasing shorter initial-link duration for the time-allocation data.
Journal of the experimental analysis of behavior, 1988 · doi:10.1901/jeab.1988.49-351