Chained schedules of avoidance: Reinforcement within and by avoidance situations.
In chained avoidance, real shocks in the last link slow responding in the first link—plan your aversive chains knowing the end controls the start.
01Research in Context
What this study did
Herrnstein et al. (1979) built a two-link chain where the first link produced the second link. In the first link, a rat pressed a lever to move to the second link. In that second link, shocks came on a set timer. Faster pressing in the second link postponed shocks. The team varied how often shocks were set to arrive and watched what happened in both links.
This let them see if shocks that actually happened in the second link changed how the rat worked in the first link.
What they found
When the second link held a faster shock timer, rats pressed more there. Yet each real shock they felt made them slow down back in the first link. The first link did not care about the posted shock rate; it cared about how many shocks the animal had just felt.
This is the opposite of food chains, where bigger food in the last link speeds up the first link.
How this fits with other research
Lendenmann et al. (1982) ran a food version of the same two-link chain. Longer food in the last link raised rates in the first link. The direction is flipped: food chains speed up when the final prize grows; shock chains slow down when the final pain lands.
Adams et al. (1966) added a third link with monkeys. They showed that even the signal for an upcoming avoidance trial can act like a mini-shock and control behavior two steps away. This stretches the chained-avoidance idea into more complex layers.
Slaton et al. (2016) took the chain idea into a classroom. Chained schedules beat multiple schedules at cutting stereotypy and boosting toy play. The lab rule—later links steer earlier links—holds whether the consequence is shock or brief toy time.
Why it matters
When you build task chains that end in an aversive event—like a hard math sheet that ends in possible reprimand—watch what really happens in the last step. Each aversive event that slips through will drag down motivation in the earlier steps. You can buffer this by tightening the final contingency or by adding safety signals learned from Wilkie et al. (1981). Treat the last link as the thermostat for the whole chain.
Get CEUs on This Topic — Free
The ABA Clubhouse has 60+ on-demand CEUs including ethics, supervision, and clinical topics like this one. Plus a new live CEU every Wednesday.
Track each aversive event that occurs in the final step of your task chain and graph how often it happens—if rates climb, add prompts or shorten the chain before early-link responding drops.
02At a glance
03Original abstract
Four rats were exposed to chained schedules with variable-cycle avoidance in both links. Responding in the initial link cancelled shocks scheduled once per minute and, according to a conjoint fixed-ratio schedule, produced a terminal link where scheduled shock rates varied from 0 to 8 shocks per minute in different conditions of the experiment. Response rates in the terminal link increased as a function of the scheduled shock rate. Response rates in the initial link, on the other hand, decreased as a function of the shock rate actually received (rather than scheduled) in the terminal link. While consistent with other studies of aversive control, these results differ from those obtained in chained schedules of positive reinforcement in that increases in reinforcement within the terminal link of the chain did not systematically increase the reinforcing value of that link.
Journal of the experimental analysis of behavior, 1979 · doi:10.1901/jeab.1979.32-399