How Odors Influence Human Perception of Color

Tuesday - October 10 2023, 06:52 UTC - 1 year ago

A study conducted by the Frontiers in Psychology has uncovered how odors can strongly influence our perception of colors, such that the presence of certain smells will make us perceive a ‘neutral’ color differently. For example, the presence of coffee may unconsciously make us perceive grey as more of a reddish-brown, while the presence of lemon may unconsciously make us perceive grey as a more yellowish color. Additionally, the authors have discussed potential implications of this influence in the field of marketing and behavior modification.

Our five senses bombard us with environmental input 24/7. One way our brain makes sense of this abundance of information is by combining information from two or more senses, such as between smells and the smoothness of textures, pitch, color, and musical dimensions. This sensory integration also causes us to associate higher temperatures with warmer colors, lower sound pitches with less elevated positions, and colors with the flavor of particular foods – for example, the taste of oranges with the color of the same name.

Now, a study recently published in Frontiers in Psychology has shown experimentally that such unconscious ‘crossmodal’ associations with our sense of smell can affect our perception of colors.

"Here we show that the presence of different odors influences how humans perceive color," said lead author Dr Ryan Ward, a senior lecturer at Liverpool John Moores University in Liverpool, UK.

Ward and colleagues tested for the existence and strength of odor-color associations in 24 adult women and men between 20 and 57 years of age. The participants were seated in front of a screen in a room devoid of unwanted sensory stimuli for the duration of the experiments. They wore no deodorants or perfumes, and none reported being color-blind or having an impaired sense of smell.

All ambient odors in the isolation room were purged with an air purifier for four minutes. Then one of six odors (chosen at random from caramel, cherry, coffee, lemon, and peppermint, plus odorless water as a control) was broadcast into the room with an ultrasonic diffuser for five minutes.

"In a previous study, we had shown that the odor of caramel commonly constitutes a crossmodal association with dark brown and yellow, just like coffee with dark brown and red, cherry with pink, red, and purple, peppermint with green and blue, and lemon with yellow, green, and pink," explained Ward.

Participants were presented with a screen that showed them a square filled with a random color (from an infinite range) and were invited to manually adjust two sliders – one for yellow to blue, and another for green to red – to change its color to neutral grey. After the final choice had been recorded, the procedure was repeated, until all odors had been presented five times.

The results showed that participants had a weak but significant tendency to adjust one or both of the sliders too far away from neutral grey. For example, when presented with the odor of coffee, they wrongly perceived ‘grey’ to be more of a red-brown color than true neutral grey. Likewise, when presented with the odor of caramel, they wrongly perceived a color enriched in blue as grey. The presence of the smell thus distorted the participants’ color perception in a predictable manner.

An exception was when the odor of peppermint was presented: here, the participants’ choice of hue was different from the typical crossmodal association demonstrated for the other odors. As expected, the participants’ selection likewise corresponded to true grey when presented with the neutral scent of water.

"These results show that the perception of grey tended towards their anticipated crossmodal associations," the authors concluded.

The team's findings show how the five senses interact with each other in unexpected ways, and how subtle changes in one sense contribute to changes in the perception of reality, which could help shape our behavior or modify preferences. Future studies could delve further into the implications of this influence of smell on human perception of color and explore how this could be leveraged in the marketplace.