Retronasal Habituation: Characterization and Impact on Flavor Perception Using Time-Intensity
Pellegrino, R., A. Atchley, S. Ali, J. Shingleton, and C. R. Luckett.  2018.  Chemosensory Perception.

Olfactory habituation results from prolonged exposure to an odor, leading to perceptual changes defined by several characteristics. To date, human habituation research has focused on orthonasal olfaction which is perceived externally while ignoring internal routes of odor perception related to flavor. In our study, we conducted two experiments to characterize retronasal olfactory habituation and measured its impact on flavor perception. In Experiment 1, participants were presented a food odor and non-food odor retronasally, using an orally adhered strip. Each participant rated the odor intensity using a time-intensity procedure. After exposure, the participants ate a lime-flavored gummy and rated the lime flavor. In experiment 2, the same procedure was performed for a low-level lime odor, a simple (lime oil) and complex (lime oil + sucrose + citric acid) beverage as the flavor stimuli. Our results demonstrated two known principles of habituation for retronasally presented odors: (1) prolonged exposure leads to decreased perception and (2) weaker stimuli lead to more rapid habituation. Additionally, we found that the non-food odor habituated slower than the food odor; however, the participants seemed to recover simultaneously upon food and beverage consumption leading to no change in flavor perception. The findings of this study give evidence that we habituate to different odors at different rates; more specifically, we provide evidence that differentiates between odor origin and concentration. This is the first time-intensity characterization of retronasal odor habituation. Additionally, a novel method of administering retronasal odors is presented.