Stimulus and reinforcer relativity in multiple schedules: Local and dimensional effects on sensitivity to reinforcement.
Reinforcement value slides during the session—refresh stimulus disparity or component length to bring it back.
01Research in Context
What this study did
Last et al. (1984) ran pigeons on two-key multiple schedules.
Each key gave food on its own variable-interval program.
The team changed two things: how different the key colors looked and how long each color stayed on.
They counted pecks minute-by-minute to see how reinforcement sensitivity moved.
What they found
Sensitivity to reinforcement followed a power curve, not a straight line.
Bigger color differences made the birds switch keys faster.
Late in a component, sensitivity dropped even if the food rate stayed the same.
Both the look of the stimuli and the clock inside the session mattered.
How this fits with other research
Solnick et al. (1977) showed that matching needs long, stable exposure. G et al. add that, once stable, minute-by-minute drift still happens.
Kohlenberg (1973) found that short stimuli kill observing. G et al. widen this: even long stimuli lose power as the component ages.
Nevin et al. (2005) later showed more stimuli per minute raise response rate but not resistance to change. Together the pair warns us: higher moment-to-moment sensitivity does not mean stronger long-term behavior.
Why it matters
Your client may "lose motivation" late in a work session even though the token rate is flat. Before you bump the reinforcer size, try two levers: (1) make the SD colors more different and (2) shorten the component or insert a brief reset. These small timing and stimulus tweaks can restore sensitivity without extra tokens or candy.
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Join Free →Swap in high-contrast colors for the richer schedule and shorten each component by one minute; track if response allocation sharpens.
02At a glance
03Original abstract
Pigeons' responses in two successive components of multiple schedules were reinforced according to variable-interval schedules of reinforcement that varied over five different conditions. Within each session of all conditions, line orientations of 0 degrees , 30 degrees , or 45 degrees in Component 1 alternated with orientations of 45 degrees , 60 degrees , or 90 degrees in Component 2. Response rates were recorded in three successive subintervals of each component. Ratios were taken between the response rate in each Component 1 line orientation and the response rate in each Component 2 orientation. These ratios were found to be power functions of the corresponding ratios of obtained reinforcement rates. Sensitivity of response ratios to changes in reinforcer ratios, given by the value of the exponent of the power function, increased systematically with increasing disparity between the dimensional values of orientation stimuli. In addition, sensitivity decreased systematically over successive subintervals of components, that is, with increasing time since component alternation. Dimensional and local (subinterval) effects interacted in that sensitivity increased with stimulus disparity to a far greater extent in the first subinterval than later in components. The data could be described by a combination of rectangular hyperbolae which attributed the interaction between local and dimensional effects to limits set by local effects on the extent that stimulus differences could affect sensitivity.
Journal of the experimental analysis of behavior, 1984 · doi:10.1901/jeab.1984.41-69