Explaining Performance on Interval and Ratio Schedules with a Molar View of Behavior
Ratio schedules crash at lean pay because their molar unit is too small, not because the kid loses interest.
01Research in Context
What this study did
Baum (2025) built a math model that treats whole sessions as one unit. The model asks: how much behavior and how much reward fill the whole session?
He tested if this molar view could explain why ratio schedules stop working when rewards are rare while interval schedules keep going.
What they found
The model shows ratio schedules break down because their unit of analysis is tiny. One response gives one reward, so the molar unit shrinks to almost nothing.
Interval schedules survive lean pay because their unit is bigger. Time keeps ticking even when the kid is not responding, so the molar unit stays large.
How this fits with other research
Russell et al. (2018) saw the same break-down in kids with autism. When tokens got scarce on a progressive ratio, the kids quit. Baum’s math now explains why.
Gaucher et al. (2020) used a DRL interval schedule with autistic preschoolers and found the kids could keep the slow pace. The larger molar unit of interval time gave them room to adjust.
Catania (2021) argued that trial-to-trial contiguity does not drive behavior. Baum agrees and moves the lens even wider, to the whole session.
Why it matters
Next time you thin reinforcement, think in molar units. If you stay on a ratio, keep the unit big enough by clustering several responses or adding a brief time window. If you switch to an interval, let time carry some of the load so the client does not hit a wall when rewards get lean.
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02At a glance
03Original abstract
Some of the most basic phenomena in behavior analysis are the differences between performance on interval and ratio schedules. They have long been known and long puzzled over. Previous attempts to explain the performances have foundered either because they lacked a mechanism or because they adopted a molecular view of behavior based on discrete responses and contiguity. The molar view of behavior offers the sought-for explanation of differences in activity rate and the inability of ratio schedules to maintain activity at low food rates. The present account relies on induction by phylogenetically important events (PIE) according to power functions, molar feedback functions, and the framework of matching theory. A model described by a feedback system with all parameters the same predicts the relations between activity rate and PIE rate. The difference in overall activity rate arises from a difference in units of activities selected by ratio and interval schedules. The results demonstrate the greater explanatory power of the molar view of behavior.
Perspectives on Behavior Science, 2025 · doi:10.1007/s40614-025-00455-3