Resistance to extinction versus extinction as discrimination

The hypothesis that response strength might be measured by persistence of responding in the face of extinction was discredited in the 1960s because experiments showed that responding persists longer following intermittent reinforcers than following continuous reinforcers. Instead, researchers proposed that the longer persistence following intermittent reinforcers arises because intermittent reinforcement more closely resembles extinction—a discrimination theory. Attention to resistance to extinction revived because one observation seemed to support the persistence hypothesis: Following training on a multiple schedule with unequal components, responding usually persisted longer in the formerly richer component than in the formerly lean component. This observation represents an anomaly, however, because results with single schedules and concurrent schedules contradict it. We suggest that the difference in results arises because the multiple-schedule procedure, while including extensive training on stimulus discrimination, includes no training on discrimination between food available and food unavailable, whereas comparable single- and concurrent-schedule procedures include such training with repeated extinction. In Experiment 1, we replicated the original result, and in Experiment 2 showed that when the multiple-schedule procedure includes training on food/no-food discrimination, extinction following multiple schedules contradicts behavioral momentum theory and agrees with the discrimination theory and research with single and concurrent schedules.     

Resistance to extinction in evaluative conditioning

A well-demonstrated phenomenon in traditional Pavlovian conditioning research with humans is that of experimental extinction. In contrast, human evaluative conditioning research suggests that evaluative learning shows marked resistance to extinction. Here, the authors replicate both findings concurrently. Two differential fear conditioning experiments with an electrocutaneous stimulus as the unconditioned stimulus evidenced (a) sensitivity to extinction using an autonomic skin-conductance measure and (b) complete resistance to extinction using an affective-priming measure. The results corroborate the idea that evaluative conditioning is more resistant to extinction than is expectancy learning (F. Baeyens, P. Eelen, & G. Crombez, 1995).     

Resistance to extinction in the steady state and in transition

Three experiments with pigeons explored the constancy of reinforcer omission during extinction conjectured by rate estimation theory. Experiment 1 arranged 3-component multiple variable-interval (VI) schedules with a mixture of food and extinction trials within each session. Reinforcers omitted to an extinction criterion increased with food-trial reinforcer rate. Experiment 2 arranged 3-component multiple VI schedules where components differed in rate or number of reinforcers. Resistance to extinction depended on the training reinforcer rate but not on the number of reinforcers omitted. Experiment 3 replicated the partial-reinforcement extinction effect within subjects in a discrete-trial procedure and found that more reinforcers were omitted in continuous- than in partial-reinforcement trials. A model of extinction based on behavioral momentum theory accounted for all the data.     

Resistance to extinction following habituation to behaviourally disruptive novel stimuli

Three experiments tested the prediction, derived from generalized frustration theory (Amsel, 1972), that habituation to behaviourally disruptive stimuli increases resistance to extinction in the runway. In each experiment, rats received initial consistent reinforcement (CRF) training and then either continued CRF (Groups C), partial reinforcement (PRF) training (Groups P), or CRF accompanied by presentations of a novel tactile, tone, or obstacle stimulus (Groups D) in Experiments 1-3, respectively. PRF increased resistance to extinction whether non-reinforcement disrupted behaviour (Experiment 1) or not (Experiments 2 and 3). The tactile and obstacle stimuli very substantially disrupted behaviour, and the tone produced a modest disruption of behaviour. All subjects habituated to the disruptive effects of these stimuli, but Group D was not more resistant to extinction than Group C in any experiment. The results suggest that non-reinforcement has unique stimulus properties, a consequence of which is that habituation to other sources of disruptive stimulation does not promote responding to non-reinforcement in extinction.     

Resistance to extinction of human evaluative conditioning using a between-subjects design

Two experiments were conducted to examine whether the resistance to extinction obtained in evaluative conditioning (EC) studies implies that EC is a qualitatively distinct form of classical conditioning (Baeyens, Eelen, & Crombez, 1995 a) or whether it is the result of an nonassociative artefact ( Field & Davey, 1997 , 1998 , 1999 ). Both experiments included between-subjects control groups in addition to standard within-subjects control conditions. In Experiment 1, only verbal ratings were measured in order to evaluate the effect of postacquisition CS-only exposures on EC whereas in Experiment 2, verbal ratings and postextinction priming effects were measured. The results showed that the EC effects are demonstrable in a between-subjects design and that the extinction procedure did not have any influence on the acquired evaluative value of CSs regardless of whether the verbal ratings or the priming effects were used as dependent variables. The present results provide evidence that EC is resistant to extinction and suggest an interpretation of EC as a qualitatively distinct form of associative learning.     

Resistance to extinction following variable-interval reinforcement: reinforcer rate and amount

Rats obtained food-pellet reinforcers by nose poking a lighted key. Experiment 1 examined resistance to extinction following single-schedule training with different variable-interval schedules, ranging from a mean interval of 16 min to 0.25 min. That is, for each schedule, the rats received 20 consecutive daily baseline sessions and then a session of extinction (i.e., no reinforcers). Resistance to extinction (decline in response rate relative to baseline) was negatively related to the rate of reinforcers obtained during baseline, a relation analogous to the partial-reinforcement-extinction effect. A positive relation between these variables emerged, however, when the unit of extinction was taken as the mean interreinforcer interval that had been in effect during training (i.e., as an omitted reinforcer during extinction). In a second experiment, rats received blocks of training sessions, all with the same variable-interval schedule but with a reinforcer of four pellets for some blocks and one pellet for others. Resistance to extinction was greater following training with the larger (four pellets) than with the smaller (one pellet) reinforcer. Taken together, these results support the principle that greater reinforcement during training (e.g., higher rate or larger amount) engenders greater resistance to extinction even when the different conditions of reinforcement are varied between blocks of sessions.