Acquisition and retention of verbal associations to olfactory and abstract visual stimuli of varying similarity.

The similarity among a set of stimuli used in a paired-associate (PA) task was controlled by psychological scaling. Three lists of odorants and two lists of abstract figures (forms) with six stimuli in each list were constructed to have varying degrees of intralist similarity. Independent groups learned to associate digit responses with one stimulus list in a PA training session. Recognition of training stimuli presented among 12 distractor stimuli and recall of the associations was tested after 7 days. Within each modality, increased intralist similarity impaired PA acquisition. Between modalities, acquisition was inferior with the odor stimuli. During recognition testing, the olfactory modality supported inferior performance. In recall testing, equivalently learned responses in the two modalities were equally well retained. There appears to be a perceptual limitation in olfaction relative to vision that influences stimulus encoding and stimulus retrieval processes but that does not affect retrieval of associated responses.