Construction of a measurement system for simultaneity judgment using odor and taste stimuli

The modalities examined in previous simultaneity judgment (SJ) were limited to vision, audition, and touch. By contrast, olfaction and gustation have not been addressed to date in SJ.

In this study, we constructed a measurement system for performing SJ with three cross-modal, combinations of odor, taste, and light stimuli. Odor and taste stimulators were able to stimulate to only the receptors corresponding to the modalities of each stimulus, without inducing tactile sensation. Furthermore, in order to precisely calculate the time points at which stimulus reached receptors in each trial, we monitored the presented stimuli in real time. After we calculated the actual values of stimulus onset asynchrony (SOA) between standard and comparison stimuli on the basis of the records of real-time monitoring, we evaluated the temporal distributions of simultaneous response rates in each cross-modal combination.

When we fitted a Gaussian distribution to these temporal distributions, we observed low error rates in all cross-modal combinations, as demonstrated in SJ using visual, audio, and tactile stimuli.

SJ using chemical stimuli and SJ using physical stimuli exhibit the same degree of measurement accuracy.

We succeeded in development a high accurate measurement system for SJ using chemical stimuli. We attribute this success to the use of strict real-time monitoring of stimulus presentation.