The perception of odor quality as stimulus concentration changes: Constancy and process dissociation in olfaction

This paper explores how the quality of an odor changes as its concentration is increased. In Experiment 1, participants rated degree of presence for various qualities and stimulus intensity, for seven odors at five concentrations. Degree of presence ratings for a particular quality increased more rapidly across concentration when the exemplar of that quality resembled the target odor. In Experiment 2, participants rated quality, intensity, and similarity to an exemplar of the target quality, for three odors, at four concentrations. Intensity increased across concentration, similarity remained constant though different between odors, and quality ratings changed at a rate dependent upon the interaction of similarity and intensity. Modeling further confirmed this. Experiment 3 repeated Experiment 2 using new odors and a new quality, and obtained similar results. These data suggest that odor quality judgments of the form 'How [quality] does this smell?' combine two independent sources of information, quality exemplar similarity and intensity, mirroring the same dissociation observed in neuropsychological data. In addition, at least over the concentration range employed here, the dominant quality remained recognizable suggesting perceptual constancy.