The nose tells it to the eyes: crossmodal associations between olfaction and vision

Crossmodal linkage between the olfactory and visual senses is still largely underexplored. In this study, we investigated crossmodal olfactory-visual associations by testing whether and how visual processing of objects is affected by the presence of olfactory cues. To this end, we explored the influence of prior learned associations between an odour (eg odour of orange) and a visual stimulus naturally associated with that odour (picture of orange) on the movements of the eyes over a complex scene. Participants were asked to freely explore a photograph containing an odour-related visual cue embedded among other objects while being exposed to the corresponding odour (subjects were unaware of the presence of the odour). Eye movements were recorded to analyse the order and distribution of fixations on each object of the scene. Our data show that the odour-related visual cue was explored faster and for a shorter time in the presence of the congruent odour. These findings suggest that odours can affect visual processing by attracting attention to the possible odour source and by facilitating its identification.