Choice in the time-left procedure and in concurrent chains with a time-left terminal link.
Basic choice rules explain timing decisions, so extra timing theories may be unnecessary.
01Research in Context
What this study did
Preston (1994) compared two ways to run a choice test.
Rats picked between two levers in a concurrent-chain setup.
One terminal link used a time-left schedule.
The other used a plain fixed-interval schedule.
The team asked: do we need special timing rules to explain the pattern, or will basic choice math do?
What they found
The rats’ choices followed the same equations that work for any concurrent-chain schedule.
No extra “clock” or “timer” rule was needed.
Time-left behavior looked like ordinary delay-reduction.
How this fits with other research
Arantes et al. (2008) seems to disagree.
They showed pigeons switched timing choices when the room color changed.
They said Scalar Expectancy Theory was needed to explain the shift.
The two studies differ in species, cues, and measures, so both can be true.
Dougherty et al. (1996) extend the same idea.
They proved that a fixed delay gap, not a ratio, steadies preference.
Together the papers build one rule: animals pick the path that shortens wait time, no clock module required.
Fantino (1969) set the stage by showing choice tracks relative expected wait time, the core math Preston (1994) applied.
Why it matters
You can treat “timing” problems as plain choice problems.
When you write a concurrent-chain program, focus on the delay difference between terminal links.
Skip extra timing prompts or special cues unless your data say they help.
Test simple choice equations first; add timing rules only if the basic model fails.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Plot the wait time to reinforcement for each chain; adjust delays, not cues, to shift preference.
02At a glance
03Original abstract
In two experiments, rats chose between a standard fixed-duration food-associated stimulus and a stimulus whose duration was the time remaining to reinforcement in an elapsing comparison interval. In Experiment 1, 4 rats responded in a time-left procedure wherein a single initial-link variable-interval schedule set up two potential terminal links simultaneously. As time elapsed in the initial-link schedule, the choice was between a standard fixed-interval 30-s terminal link and a time-left terminal link whose programmed interval requirement equaled 90 s minus the elapsed time in the initial link. Rats generally responded more on the lever with the shortest programmed terminal-link duration, but the temporal parameters of the procedure were found to vary with response distributions. Contrary to previous reports, therefore, time-left data were well predicted by choice models that make no assumptions about animal timing. In Experiment 2, 8 rats responded on a concurrent-chains schedule with independent variable-interval initial links and a time-left terminal link in one of the choice schedules. On the time-left lever, the programmed terminal-link delay equaled 90 s minus the elapsed time in the time-left initial link. On the standard lever, terminal-link responses were reinforced according to a variable-interval schedule whose average value varied over four conditions. Relative time-left initial-link responses increased in the elapsing time-left initial-link schedule as the time-left terminal link became shorter relative to the standard terminal link. Scalar expectancy theory failed to predict the resultant data, but a modified version of the delay-reduction model made good predictions. An analysis of the elaboration of scalar expectancy theory for variable delays demonstrated that the model is poorly formulated for arithmetically distributed delays.
Journal of the experimental analysis of behavior, 1994 · doi:10.1901/jeab.1994.61-349