Context Effect on Temporal Resolution of Olfactory–Gustatory, Visual–Gustatory, and Olfactory–Visual Synchrony Perception

Olfactory-gustatory simultaneity judgments: A preliminary study on the congruency-dependent temporal window of multisensory binding

BACKGROUND

A greater congruency of audio and video expands the temporal binding window (TBW). A similar phenomenon may occur with a combination of odor and taste, which are the main components of flavor.

OBJECTIVE

TBW is defined as the temporal resolution of synchrony perception. The larger the TBW, the lower the resolution. We hypothesized that the more congruent the odor and taste, the lower the temporal resolution of synchrony perception.

METHODS

To examine this hypothesis, 10 female participants performed simultaneity judgment (SJ) tasks under congruent (soy sauce odor with saline) and incongruent (cherry tree leaf odor with saline) conditions and evaluated the congruency with saltiness for the two odors. In the SJ tasks, participants reported whether odor and taste were presented simultaneously or successively. We assumed a Gaussian distribution for the temporal distributions of the simultaneous response rates and calculated the approximations. In addition, we computed the half width at half height (HWHH) as an index of TBW based on the coefficient of approximation for the temporal distribution of the simultaneous response rates.

RESULTS

HWHH was significantly larger under congruent condition than under incongruent condition. In addition, congruency with saltiness had a significant moderate positive correlation with HWHH.

CONCLUSION

The larger the HWHH, the lower the temporal resolution of synchrony perception, supporting the hypothesis. This study suggests that the width of TBW depends on the cross-modal congruency similar to the case for audio-visual SJs. However, methodological improvements, including a larger sample size and gender-independent recruitment of participants, are essential to enhance the reliability of the findings because some of the results did not provide sufficient ESs or power.

Odor-Induced Taste Enhancement Is Specific to Naturally Occurring Temporal Order and the Respiration Phase

Interaction between odor and taste information creates flavor perception. There are many possible determinants of the interaction between odor and taste, one of which may be the somatic sensations associated with breathing. We assumed that a smell stimulus accompanied by inhaling or exhaling enhances taste intensity if the order is congruent with natural drinking. To present an olfactory stimulus from the identical location during inhalation and exhalation, we blocked the gap between the tube presenting the olfactory stimulus and the nostril. Participants breathed and ingested the solution according to the instructions on the screen and evaluated the solution's taste intensity. Vanilla odor enhanced the sweet taste in both retronasal and orthonasal conditions when the order of stimuli was congruent with natural drinking, but it did not do so in either condition when they were incongruent. The results suggest that breathing is a determinant of odor-taste interaction. The methods of presenting olfactory stimuli used in this study were compared and discussed in relation to those used in previous studies. Odor-induced taste enhancement depends on the time order of smell with breathing and taste congruency in natural drinking. Taste enhancement was induced by odor in both conditions by minimizing differences in odor presentation between them.