Can smell impact visual perception?

BioTechniques News
Aisha Al-Janabi

Odors seem to impact our visual perception of colors, adjusting our perception of a ‘neutral’ color.

A recent study first authored by Ryann Ward of Liverpool John Moores University (UK), has revealed our sense of smell can bias our visual perception of colors. To do so, they used a sensory-deprived room to expose participants to different smells while monitoring their identification of a neutral grey. The study prompts further questions regarding the extent of this association and the impact of “crossmodal associations” on our daily lives.

In a previous study 2 years prior, Ward and his team had identified that distinct smells were associated with different colors. For instance, the odor of coffee was associated with dark brown and red whilst the smell of lemons was associated with green, pink and yellow.

Building on this work to determine whether this association could actually influence visual perception, the team assembled a cohort of 24 people between 20 and 57 years of age with no reported color blindness or sense of smell impairments. Participants were directed not to wear any deodorants or perfumes and placed in a room deprived of sensory stimuli, save for a screen.

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An ultrasonic diffuser was used to infuse the room with the scent of caramel, cherry, lemon, coffee, peppermint and odorless water one at a time, using an air purifier to purge the room of ambient odors in between each diffusion. During each infusion, the screen in front of the participant was filled with a random color and the participant was directed to use two sliders to control the red–green and yellow–blue balance of the color until it reached a neutral grey.

The results demonstrated that for all of the odors, barring the control, the participants adjusted one or both of the scales incorrectly, landing on a color that was not neutral grey. All of these adjustments were towards a warmer color, which was expected for four of the five odors that were associated with warmer colors.

Furthermore, within the warm color range, these color shifts tracked closely to the previously identified crossmodal associations with lemon shifting towards yellow–green and coffee inducing a shift towards red–brown. Peppermint, however, which had previously been associated with green and blue, also induced a shift towards a warmer color, deviating from its typical crossmodal association and the researchers’ predictions.

Commenting on the results, Ward noted that “This ‘overcompensation’ suggests that the role of crossmodal associations in processing sensory input is strong enough to influence how we perceive information from different senses, here between odors and colors.” Next, the team will look to examine the extent of this impact and how closely it associates with an individual’s familiarity with the odors encountered.

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