Treatments that weaken Pavlovian conditioned fear and thwart its renewal in rats: implications for treating human phobias.

In experiments using a total of 144 albino rat subjects, the authors assessed the ability of fear-weakening treatments to prevent fear renewal (relapse). Conditioned suppression of operant behavior served as the measure of fear in an A-B-A (acquisition-treatment-test) renewal paradigm. In Experiment 1, 100 nonreinforced exposures to a feared cue during treatment (extinction) did not reduce fear renewal relative to 20 exposures. In Experiment 2, explicitly unpaired (EU) treatments thwarted both renewal and reacquisition. In Experiment 3, conditioned inhibition (CI) and differential conditioning (DC) treatments weakened renewal and resisted both reacquisition and a form of reinstatement. In Experiment 4, EU, DC, and CI treatments all thwarted renewal. Evidence suggested that the ability of the treatments to do so reflected the combined effects of transfer of extinction across treatment and test contexts and habituation to the unconditioned stimulus.