On the measurement of time allocation on multiple variable-interval schedules.
On multiple VI schedules, local response rate stays steady while time allocation shifts with food rate—check your data partitioning before modeling.
01Research in Context
What this study did
Researchers put pigeons on two VI schedules that alternated in the same session. They counted how many pecks came in each component and how long the birds stayed there.
They changed the rate of food delivery across components to see what moved: response rate, time allocation, or both.
What they found
When food arrived faster in one component, birds spent more time there and pecked more overall. Yet the local pecks per second stayed the same within each component.
In plain words: time shifted, but the moment-to-moment speed of pecking did not.
How this fits with other research
Rutter et al. (1987) ran the same birds the next year and got the same pattern even when components switched after a set number of pecks instead of after minutes.
Pliskoff et al. (1978) saw the same local-rate constancy on concurrent VI schedules, adding that a short changeover delay keeps pecking high for three seconds after a switch.
Neuringer et al. (1968) had already shown that time allocation matches food rate even when food is response-independent, so the new paper tightens the lens to multiple schedules.
Why it matters
If you plot only total responses, you might think the bird is working harder. Check time allocation first; the local rate may be flat. This keeps you from over-interpreting small jumps in counts during schedule thinning or when you add new components to a token board.
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02At a glance
03Original abstract
Six pigeons were trained on a modified multiple-schedule procedure. In a three-key chamber, the center key was lighted red or green, depending upon which component schedule was in effect. A response on this key transferred this color to each of two side keys, and responses on one of those keys produced reinforcers according to the component schedule. After 2 s, the side-key lights were extinguished, the center key was reilluminated, and a further center-key response was required to give access, as before, to the component schedules. Components alternated every 3 min. This limited-access procedure allowed both times spent switched into the side keys and time spent not switched in to be measured in the two components. Component reinforcer rates were varied over eight experimental conditions. Both component response rate and component time allocation were increasing functions of relative component reinforcer rate, and these functions were not significantly different. This finding implies that local response rates (responses divided by time switched in) were unaffected by changing component reinforcer rates on multiple schedules. Because a similar result was recently obtained for concurrent schedules, models of multiple and concurrent-schedule performance may need to consider only the time allocation of behavior emitted at equal tempo in the component schedules.
Journal of the experimental analysis of behavior, 1986 · doi:10.1901/jeab.1986.46-353