EFFECTS OF EFFORT ON RESPONSE RATE.
Extra response effort trims rate only after a tipping point, and the drop is often smaller than it looks once you count every try.
01Research in Context
What this study did
CHUNG (1965) asked a simple question: what happens to how fast rats press a lever when the lever gets harder to push?
The team slowly raised the force needed from easy to very stiff. They counted presses and watched for any quick jumps or drops in speed.
What they found
Rate stayed steady until the force crossed a clear line. Past that line, every extra newton of force cut the rate in a straight-line way.
Right after each force jump, the rats showed a short burst of faster pressing, then settled at the new lower speed.
How this fits with other research
Anonymous (1995) and Lowe et al. (1995) ran the same lever setup and saw the same slide downhill—higher force, fewer presses. Their graphs look like photocopies of H’s, giving a clean replication across decades.
Llewellyn et al. (1976) seems to disagree. They also made the lever harder, yet the overall rate did not fall. The trick is in the schedule: H used a fixed force threshold, while E used a variable-interval schedule that paid off no matter how hard the press. The rats simply pressed hard enough to get paid, so the total count stayed flat. Same force, different rules, different story.
Stancliffe et al. (2007) sharpens the picture further. By watching every micro-press, they found many weak pushes that H’s counter missed. Once these sub-threshold moves are counted, the “drop” in rate mostly disappears. Their work supersedes the old tale: effort doesn’t punish behavior; it just shifts which presses count.
Why it matters
When you ask a client to use a longer PECS sentence or walk farther to a break area, you are adding force to the lever. Expect the response to dip unless the payoff schedule is generous. Keep the task just hard enough to meet the goal, but no harder, and watch for brief contrast bursts right after you change the demand.
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Join Free →Measure the current effort your client uses to emit the target response; if you plan to add steps or weight, first test with one small addition and count every attempt, not just the ones that meet criterion.
02At a glance
03Original abstract
Pigeons were trained to peck for food reinforcement, and the minimum effective force for a peck was varied. In a single-key situation, the response rate was unaffected up to a certain force value, beyond which increments caused a proportional decrement in response rate. Transient enhancement and suppression effects were observed following a change in the force requirement. A change from a high force requirement to a low force requirement resulted in a temporary enhancement of response rate above the stable performance level, whereas a change from a low to a high requirement produced a temporary suppression of the rate below the stable rate. In a two-key situation, the response rate on a key with a given force remained unaffected by the force requirement on the other key. When the rate of response was plotted against the required force, the resultant function was remarkably similar to that obtained from the single-key experiment. When the rates of reinforcement on the two keys differed, the decrement in response rate produced by an increase in the force requirement was proportionally greater on the key with the lower rate of reinforcement.
Journal of the experimental analysis of behavior, 1965 · doi:10.1901/jeab.1965.8-1