Scents boost preference for novel fruits.

When faced with a novel food, multisensory information that includes appearance and smell is a very important cue for preference, categorization, and the decision of whether or not to eat it. We elucidated whether olfactory information leads to biased visual categorization of and preference for fruits, even when odors are presented subliminally. We employed morphed images of strawberries and tomatoes combined with their corresponding odorants as stimuli. Participants were asked to categorize the images into either of two categories, to evaluate their preference for each visual image, and to judge the presence/absence of the odor. Results demonstrated that visual categorization was not affected by the odor manipulation; however, preference for uncategorizable images increased when odors were presented regardless of the participant's awareness of the odor. Our findings suggest that visual preference for novel fruits is based on both conscious and unconscious olfactory processing regarding edibility.

Infant visual preference for fruit enhanced by congruent in-season odor.

We explored the ability of infants to recognize the smell of daily foods, including strawberries and tomatoes, by using a preferential-looking-technique. Experiment 1 was conducted while strawberries were in season (from March to June) in order to enhance the frequency of participant exposure to strawberries outside of the laboratory. Thirty-seven infants aged 6-8 months were tested with a stimulus composed of a pair of photos of strawberries and tomatoes placed side by side and accompanied by a strawberry odor, a tomato odor, or no odors. Infants showed a preference for the strawberry picture when they smelled the congruent odor, but no such preference for the tomato picture. These results suggest that even young infants can recognize olfactory-visual congruency. We conducted Experiment 2 while strawberries were out of season (from July to September) to reduce participant exposure to strawberries in their daily life. Twenty-six infants aged 6-8 months were tested with a stimulus composed of a pair of photos of strawberries and tomatoes placed side by side and accompanied by a strawberry odor, or no odors. In Experiment 2, the olfactory-visual binding effect disappeared. This implies that visual-olfactory binding is triggered by an observer's experience.

Taste of breath: the temporal order of taste and smell synchronized with breathing as a determinant for taste and olfactory integration.

Many studies have reported that subjective taste intensity is enhanced by odors which are congruent, for example a sweet taste and a vanilla odor. Some reports have suggested that subjective taste is more strongly enhanced by retronasal than by orthonasal odors; others have suggested that taste enhancements by both odor routes are identical. Differences between the two routes include the direction of airflow accompanying breath. Thus, it is possible that the order of gustatory and olfactory stimuli when breathing through either route while drinking is a determining factor for taste-odor integration. To reveal the natural relationship between taste intensity enhancement by odors and breath, synchronization of odor stimulation with the breath is necessary. Here, we examined whether the enhancement of a sweet taste is induced by a vanilla odor presented in various combinations of odor routes, immediately before and immediately after drinking. The results showed that a retronasal odor after drinking enhanced taste, but an orthonasal odor before drinking did not. The retronasal odor before drinking and the orthonasal odor after drinking did not enhance the sweet taste. These results show that congruency with the natural order of stimulus and kinetic sensation is a determining factor for odor-induced taste enhancement.