Stimulus Equivalence Classes Involving Olfactory Stimuli

Abstract

Adults were trained on a matching-to-sample task which initially involved matching either familiar, distinctive odor stimuli (smells) or less familiar, less distinctive stimuli (perfumes) with nonsense syllables (A→B training). If they met a criterion of successful performance, they were transferred to a task where they had to match nonsense syllables to line drawings (B→C training). Following successful performance, there was a test phase where the line drawings were presented as samples with the odors as comparison stimuli (C→A test phase). All participants who successfully completed A→B training also successfully completed B→C training, and 12 out of 14 selected the correct comparison stimuli on 100% of C→A test trials, with one further participant achieving 97% success. This indicates that stimulus equivalence class formation had occurred, where one element of each stimulus class was an olfactory stimulus. Some participants failed to complete A→B training successfully in the more difficult perfumes condition. This is consistent with literature from other learning paradigms. These findings have extended the generality of stimulus equivalence class formation and have implications for the role of verbal labeling. This experiment also adds significantly to the growing body of recent literature which indicates similarities between olfactory memory and that involving other modalities.