Why does the sense of smell vanish in the mouth? Testing predictions from two accounts.

When participants perceive flavor they do not recognise the role of smell. We examined two possible accounts of why: (1) a common attentional channel activated by taste; and (2) prior learning between taste and smell. Participants were asked to sniff food-related odors with a fluid in their mouth and profile each odor after expectorating. This process was later repeated for each odor, with some odors experienced with water on both occasions, and others with water on one occasion and sucrose (weak or strong) on the other. We investigated how reliable these odor profiles were and whether they were influenced by prior odor-taste learning (indexed by odor sweetness). For non-sweet smells, the presence of a tastant significantly improved profile reliability relative to water in the mouth. For sweet smells, tastant had no effect, which we suggest represents a cancelling out of the beneficial effects of the common attentional channel by the detrimental effects of prior learning. Thus, both mechanisms may contribute to masking the modal identity of smell thereby contributing to flavor binding.