Olfactory crossmodal redirection for improving perceptual experiences in virtual reality

Abstract

Virtual reality (VR) environments rely on multisensory integration to create convincing perceptual experiences, but delivering many distinct odours is costly and technically challenging. We tested whether visual context is associated with context-dependent differences in evaluations of a compressed odour set in VR. Thirty participants viewed 20 distinct visual scenes while experiencing four odour blends representing floral, citrus, woody, and oriental; eight control scenes received randomly assigned blends or no odour. The family-congruent conditions reused the same physical odour blend across different visual contexts, and linear mixed-effects models (LMMs) assessed associations between the observed visual-odour conditions and the perceptual and physiological outcomes. The LMMs showed variation between visual stimulus and perceived visual-odour match, smell naturalness, and heart rate variability (HRV). No statistically significant associations were observed for perceived odour intensity, pleasantness, visual naturalness, or galvanic skin response (GSR). Odour family was not associated with statistically significant variation in the subjective ratings but was associated with HRV within the observed visual-odour pairings. Exploratory within-blend comparisons showed that these effects varied across blends and outcome measures. Stimulus-level Pearson correlations were then conducted as secondary, hypothesis-guided analyses to characterise whether the observed condition-level evaluation profiles covaried with perceived visual-odour match. Perceived visual-odour match was significantly associated with perceived intensity ( r = 0.90 ), perceived pleasantness ( r = − 0.78 ), and smell naturalness ( r = 0.92 ), but not with visual naturalness, HRV or GSR. These correlations indicate that perceived match was associated with a broader perceptual profile rather than being an isolated semantic judgement of fit. This pattern may be consistent with a congruence-based account of crossmodal redirection, but we cannot prove that account. Overall, the findings indicate that the same physical odour blends were associated with selective, context-dependent differences in evaluation across visual scenes in VR.