The effects of differing response-force requirements on fixed-ratio responding of rats.
Harder levers reliably slow and pause rat pressing, so reduce force demands when client rates drop.
01Research in Context
What this study did
The team tested how hard rats had to press a lever. They used three fixed-ratio schedules: FR 5, FR 15, and FR 30.
Force started at 0.25 N (a light tap) and rose to 2.00 N (a firm push). Each rat worked under every force level.
What they found
When the lever got stiffer, rats pressed slower and paused longer. The drop was steady across all ratio sizes.
At 2.00 N, response rates fell by half and pauses doubled. Light force (0.25 N) kept rates high and pauses short.
How this fits with other research
Bradshaw et al. (1978) also saw slower rates when they swapped key pecks for lever presses. Both studies show response form matters.
Wilkie et al. (1981) found smaller sucrose volumes slowed VI lever pressing. Lowe et al. (1995) now shows higher force does the same under FR schedules. Together they map how physical and motivational loads both drag rate down.
Rose et al. (2000) proved reinforcer size shifts the ceiling (k) in matching theory. Force appears to shift the floor, giving a fuller picture of what sets response speed.
Why it matters
If a child’s task demands heavy pressure (tight button, stiff iPad), expect fewer responses and longer breaks. Lighten the force or switch to an easier topography and rates should jump back. Check your data sheets for pauses after you raise task difficulty; they may flag response effort, not lack of motivation.
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02At a glance
03Original abstract
Rats were exposed to two-component multiple schedules of food delivery. In the first experiment, 15 responses were required to produce food in both components. A downward force of 0.25 N (25 g) was always required to operate the response lever in one component. In the other, the required force was 0.25, 0.50, 1.00, or 2.00 N (25, 50, 100, or 200 g). In the second experiment, 0.25 N of force operated the lever in one component, but in the other, the force requirement for five consecutive responses at the beginning, middle, or end of each ratio was increased from 0.25 to 2.00 N. In the third experiment, the number of responses required to produce food was reduced from 15 to 5, and then to 1. Again, the effects of altering response force from 0.25 to 2.00 N were examined. In general, as response force increased in all experiments, mean response rates decreased and mean interresponse times increased.
Journal of the experimental analysis of behavior, 1995 · doi:10.1901/jeab.1995.63-331