Spontaneous recovery in US extinction

When an unconditioned stimulus (US) signals a second US, magazine entries increase after the first US (acquisition) and magazine entries decline when US-alone presentations follow acquisition (extinction). Experiments 1 and 2 replicated these effects and, in addition, tested for spontaneous recovery. In spontaneous recovery, responding in extinction recovers if some time elapses before a stimulus is tested again. Spontaneous recovery was shown when subjects received four US-alone presentations in each daily extinction session (Experiment 1) or when a 3-week testing delay followed a single US-alone presentation in each of 12 daily extinction sessions (Experiment 2). Implications for theories of extinction and spontaneous recovery are considered. (C) 1997 Academic Press.