The stay/switch model of concurrent choice.
Counting stay and switch moments gives a clearer picture of choice than the classic matching equation.
01Research in Context
What this study did
The team built a new way to predict choice. They split each option into two parts: staying put or switching away.
They tested pigeons on concurrent schedules. Food arrived at different rates on each key.
What they found
The stay/switch model fit every pattern. Old matching-law math missed some curves.
When birds earned most food on the right key, the model still tracked the few times they stayed left.
How this fits with other research
Wearden (1983) said undermatching is just fast bursts. MacDonall (2009) shows the bursts are really stay-versus-switch decisions.
Avellaneda (2025) keeps the matching law but adds Markov steps for changeovers. MacDonall (2009) goes further by giving stays and switches their own rules.
Farrant et al. (1998) saw strict matching with drug reinforcers. MacDonall (2009) finds the same birds break matching when you count stay and switch separately.
Why it matters
Next time a client splits time between two tasks, measure stays and switches, not just totals. You may see the real contingency controlling their choice.
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02At a glance
03Original abstract
This experiment compared descriptions of concurrent choice by the stay/switch model, which says choice is a function of the reinforcers obtained for staying at and for switching from each alternative, and the generalized matching law, which says choice is a function of the total reinforcers obtained at each alternative. For the stay/switch model two schedules operate when at each alternative. One arranges reinforcers for staying there and the other arranges reinforcers for switching from there. Rats were exposed to eight or nine conditions that differed in the arrangement of the values of the stay and switch schedules. The generalized matching law described preferences when arrangements were similar to those found when using two concurrently running interval schedules. It did not, however, describe all preferences when using different arrangements. The stay/switch model described all preferences in one analysis. In addition, comparisons of selected conditions indicated that changing the ratio of obtained reinforcers was neither necessary nor sufficient for changing preference as measured by response ratios. Taken together these results provide support for the stay/switch model as a viable alternative to the generalized matching law and that the critical independent variable is allocation of stay and switch reinforcers.
Journal of the experimental analysis of behavior, 2009 · doi:10.1901/jeab.2009.91-21