Extinction, spontaneous recovery and reinstatement in the garden snail, Helix aspersa

Extinction and its related phenomena are central to the study and development of associative learning theory. For a better understanding of the processes involved in extinction, it is important to know how general these phenomena are in different species. Extensive evidence of extinction in invertebrate species would be necessary in order to test the generality of its current theoretical and physiological accounts. We carried out three sets of experiments using terrestrial snails Helix aspersa. The repeated nonreinforced presentation of the conditioned stimulus (CS) resulted in a decrease in responding (extinction); the introduction of a delay between the extinction of a CS and its test produced an increase in responding (spontaneous recovery); and re-exposure to the unconditioned stimulus after extinction also led to an increase in responding (reinstatement). The results are discussed in relation to current interference theories of extinction.