Cross-modal impacts of olfactory perception and individual differences in emotional responses to odours modulate hedonic evaluations of visual scenes

In line with the critical role of human olfaction in motivated behaviour, positively valenced odours have been shown to boost hedonic perception of visual stimuli, especially facial expressions, compared to unpleasant smells. However, it remains unclear whether pleasant fragrances, which vary in character and subjective affective profile, differentially impact different categories of visual stimuli. We also postulate that individual differences in emotional responses to odours modulate their subsequent effect on hedonic evaluations of images. The current study investigated how (relative to a clean air control) four pleasant odours (vanilla, rose, lavender and lemon) influenced hedonic ratings of different categories of visual images (faces, landscapes, and objects), with each category comprising images of neutral and positive valence. 40 participants (aged 18-35) rated the pleasantness of each image during each odour condition presented using a computer-controlled olfactometer. Participants also reported their emotional response to each fragrance on seven dimensions (happiness, disgust, relaxation, thirstiness, sensuality, energy, nostalgia) the Liverpool Emotion and Odour Scale (LEOS), self-report questionnaire. Pleasant odours significantly affected image pleasantness ratings, but the effects of specific fragrances differed by image category. Individual differences in emotional experiences elicited by each fragrance were shown to modulate the impact of odours on hedonic evaluations, and these effects varies across the different image categories. The findings offer new insights into the differential effects of pleasant odours on hedonic evaluations of visual stimuli and the role of individual affective processing in cross-modal olfactory-visual integration.