Perceptual odor blending is influenced by chemical complexity of odorant mixtures

International audiencePerfumers and flavorists are familiar with odor blending phenomenon and often report that a minimum number of odorants has to be mixed for a good odor blend to arise. Previous studies in humans and animals suggested that a configural process could be involved in the perceptual analysis of mixtures of odorants. It has been proposed that the perceptual blending phenomenon corresponds to a configural perception of odorant mixtures. In the present study, we investigated the influence of chemical complexity on the configural perception of odorant mixtures. Six mixtures including 2 to 6 odorants as well as each unmixed odorant were assessed for their odor quality by a panel of 55 healthy untrained subjects (Ss). Two verbal description tasks were performed: Free Description and Choice between Attributes. For each mixture, a target odor name was expected; i.e. a name for odor quality emerging from each mixture through the perceptual blending phenomenon. A typicality rating task was also performed. In this task, Ss had to rate, on a linear scale, how typical was the stimulus in relation to the target odor name. Analysis of typicality ratings as well as comparison of the frequency of quotation of the target names, in both verbal tasks, between the mixtures and their components, revealed that perceptual blending did occur in 2 of the tested mixtures. Indeed the typicality was found to be significantly higher for mixtures as compared to their components and mixtures were more often described with the expected target name as compared to their components. Moreover it appeared that perceptual blending was more pronounced in the mixtures containing the higher number of odorants. Taken together, these findings confirm that mixtures of odorants can be perceived in a configural way by humans and that such a configural process may explain why odorant mixtures can elicit novel odor percepts. Additionally, we propose that a configural process would be more likely engaged when more than 4 odorants are mixed which is in line with the limit in the capacity of humans to identify odorants in a mixture (Laing & Francis, 1989)