10 October 2023

Smell affects a person's perception of color, study shows

Researchers at the University of Liverpool have studied how cross-modal connections between olfaction and vision manifest themselves. The analysis showed that certain strong scents can distort normal color perception.

The researchers tested the existence and strength of odor-color associations in 24 adult women and men between the ages of 20 and 57. Participants sat in front of a screen in a room devoid of unwanted sensory stimuli. 

All ambient odors in the isolation room were removed using an air purifier for four minutes. Then one of six odors (randomly selected: caramel, cherry, coffee, lemon, and mint, with odorless water as a control) was broadcast into the room using an ultrasonic diffuser for five minutes.

The participant was then shown a square filled with a random color (from an infinite range) and they were asked to manually adjust two controls - one from yellow to blue and the other from green to red - to change the color of the square to gray. The same procedure was repeated for different odors.

The results showed that exposure to the odors had a weak, but significant enough to be chance, effect on color perception. For example, when coffee odor was sprayed, the resulting neutral "gray" was closer to red-brown. And the smell of caramel, shifted all participants' perceptions of neutral gray toward yellow. 

The senses supply the information collected in a 24-hour stream. One way the brain manages such data streams is by integrating information from two or more senses, such as smells and smoothness of textures, pitch of sound, color, and musical dimensions.

Because of this sensory integration, high temperatures, for example, are associated with warm colors. Investigating such connections will help to better understand the principles of brain function, the study authors believe.
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