Duration-reduction of avoidance sessions as negative reinforcement.
Animals will work to end an aversive session early—session-length reduction is negative reinforcement.
01Research in Context
What this study did
Mellitz et al. (1983) worked with five rats in a standard lever box.
Each session delivered mild shocks until the rat pressed the correct lever.
One lever ended the whole session early. The other did not.
The team flipped the levers back and forth to be sure the effect was real.
What they found
Four of the five rats quickly switched to the lever that shortened the session.
The rats worked to escape the session itself, not just the next shock.
Cutting session time acted as negative reinforcement.
How this fits with other research
Hineline (1970) already showed rats will press a lever that only delays shocks.
Mellitz et al. (1983) took the next step: animals will work to end the whole aversive period.
Peterson (1968) proved that experienced shock reduction matters more than the chance of avoidance.
The new study keeps the same rule but moves the reduction up one level—from fewer shocks to a shorter session.
Why it matters
Your clients may work to escape the therapy room, not just the task.
Offer a clear way to “earn the exit” after brief, successful work.
A two-minute burst with a guaranteed finish can replace a long, grinding session.
Think session-length contracts, not just trial-by-trial breaks.
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02At a glance
03Original abstract
Five rats were exposed to a shock-postponement procedure in which responses on each of two levers initially had equivalent effects. After an initial training sequence that ensured at least some responding on each lever, an additional consequence was made conjointly operative on the previously less-preferred lever for each animal. Each response on this lever continued to postpone shock, but also reduced the session duration by one minute. The conjoint contingencies were operative until, through session-shortening responses and the passage of time, the session was scheduled to end in two minutes; during the final two minutes the session-shortening contingency was disabled while the shock-postponement contingency continued to be operative on both levers. When responding shifted to a predominance on the session-shortening lever, the conjoint contingency was shifted to the other lever; for four of the five rats this reversal was followed by two additional reversals. Two of the rats' responding showed clear, strong, and unambiguous sensitivity to the session-shortening contingency. The responding of two others was also systematically controlled by that contingency, but the effects were less clearcut. The fifth animal showed an initial shift when session-shortening was introduced, but its subsequent behavior proved insensitive to reversals of procedure. The results clearly indicate a sensitivity of behavior to events on a time scale quite distinct from that of immediate consequences. They also support an interpretation of avoidance sessions, considered in their entirety, as events whose contingent relationship to behavior can affect that behavior-even in the absence of stimuli that delineate those relationships. Finally, these results support an interpretation of aversively based conditioning within a broader context, analogous to the "open versus closed economy" interpretation of appetitively controlled behavior.
Journal of the experimental analysis of behavior, 1983 · doi:10.1901/jeab.1983.40-57