Dynamics of choice: relative rate and amount affect local preference at three different time scales.
Expect choice to linger four reinforcers after contingencies change—plan your concurrent-schedule probes around this carry-over.
01Research in Context
What this study did
Scientists watched pigeons peck two keys during daily sessions. Each key paid off with grain on its own clock. The team changed how fast and how much grain each side gave.
They zoomed in on three levels: every reinforcer, every two-minute component, and the whole session. This let them see tiny choice swings that older studies missed.
What they found
Right after a reinforcer landed, birds briefly shifted toward the other key. This pulse lasted about four reinforcers before fading.
The pulse size grew when the other key offered bigger or steadier pay. Even tiny payoff differences showed up in these local blips.
How this fits with other research
Busch et al. (2010) ran the same birds for 100 sessions. They saw the same four-reinforcer pulse, but its strength kept creeping up across days. Together, the papers show that local rules stay fixed while the impact slowly strengthens.
Landon et al. (2002) also split short-term from long-term control. They labeled effects "short" or "long," while Tyrer et al. (2009) carved the session into micro, component, and session scales. The newer frame gives clearer clinical handles.
Gomes-Ng et al. (2017) warn that pulse math alone can mislead. They urge visit analyses instead. Tyrer et al. (2009) used pulses, so clinicians should cross-check with visit counts when they copy the method.
Why it matters
When you run concurrent schedules, expect four-trial carry-over after each reinforcer. If you switch reinforcement ratios, wait at least four deliveries before you judge the new plan. Watching micro, component, and session levels together spots shifts early and saves session time.
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02At a glance
03Original abstract
To examine extended control over local choice, the present study investigated preference in transition as food-rate ratio provided by two levers changed across seven components within daily sessions, and food-amount ratio changed across phases. Phase 1 arranged a food-amount ratio of 4:1 (i.e., the left lever delivered four pellets and the right lever one pellet); Phase 2 reversed the food-amount ratio to 1:4, and in Phase 3 the food-amount ratio was 3:2. At a relatively extended time scale, preference was described well by a linear relation between log response ratio and log rate ratio (the generalized matching law). A small amount of carryover occurred from one rate ratio to the next but disappeared after four food deliveries. Estimates of sensitivity to food-amount ratio were around 1.0 and were independent of rate ratio. Analysis across food deliveries within rate-ratio components showed that the effect of a small amount was diminished by the presence of a large amount-that is, when a larger amount was present in the situation (three or four pellets), the value of a small amount (one or two pellets) became paltry. More local analysis of visits to the levers between food deliveries showed that postfood visits following a large amount were disproportionately longer than following a small amount. Continuing food deliveries from the same source tended to make visits less dependent on relative amount, but a discontinuation (i.e., food from the other lever) reinstated dependence on relative amount. Analysis at a still smaller time scale revealed preference pulses following food deliveries that confirmed the tendency toward dependence on absolute amount with continuing deliveries, and toward dependence on relative amount following discontinuations. A mathematical model based on a linear-operator equation accounts for many of the results. The larger and longer preference following a switch to a larger amount is consistent with the idea that local preference depends on relatively extended variables even on short time scales.
Journal of the experimental analysis of behavior, 2009 · doi:10.1901/jeab.2009.91-293