Odor-taste interactions in food perception: Exposure protocol shows no effects of associative learning

Repeated exposure can change the perceptual and hedonic experience of food flavors. Associative learning during which a flavor’s odor component is affected by co-exposure with taste is thought to play a central role in this process. However, changes can also arise due to mere-exposure to the odor in itself. The aim of this study was to dissociate effects of associative learning from effects of mere-exposure by repeatedly presenting one odor together with a sweet taste and another without. Sixty individuals participated in two testing sessions separated by an exposure phase during which the stimuli were presented as flavorants in chewing gums. The gums were chewed three times per day for five days. Ratings of odor sweetness, odor pleasantness, odor intensity enhancement by taste, and odor referral to the mouth were collected at both sessions. Consistent with the idea of mere-exposure, odor pleasantness increased between the sessions independently of whether the odor had been exposed with or without sucrose. However, contrary to expectation, we found no evidence for associative learning effects on any of the outcomes. In addition, exploratory equivalence tests demonstrated that these effects were either absent or insignificant in magnitude. Taken together, our results suggest that associative learning effects on odor-taste interaction are either smaller than previously thought or highly dependent on the experimental setting. Future studies are needed to dissociate these two possibilities and, if experimental settings can be identified that reliably produce such effects, to pinpoint boundary conditions that prevents associative learning from taking place.