Our sense of smell can change our perception of colors

Scientists at Liverpool John Moores University have uncovered a fascinating link between our sense of smell and our perception of colors. According to the study, the presence of different odors can directly influence how humans perceive color.

The research illuminates the unconscious “crossmodal” associations that our brain establishes among different senses, affecting our interpretation of the surrounding world.

Multisensory information 

Our five senses are constantly bombarding us with information, and one way our brain makes sense of this is by combining information from two or more senses, explained the researchers.

“Our brain constantly combines multisensory information from our surrounding environment,” wrote the study authors. “Odors for instance are often perceived with visual cues; these sensations interact to form our own subjective experience.” 

“This integration process can have a profound impact on the resulting experience and can alter our subjective reality.”

Color perception 

Lead author Dr. Ryan Ward said the study demonstrates that the presence of different odors influences how humans perceive color.

“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,” he explained.

Studying the sense of smell

For the current investigation, 24 adult participants, aged between 20 and 57 years, were tested for their association strength between specific odors and colors. 

To ensure a controlled environment, participants were placed in a sensory-deprived room that was free of any unwanted stimuli. 

With the absence of deodorants, perfumes, or any ambient odors, the researchers introduced one of six distinct odors: caramel, cherry, coffee, lemon, peppermint, or odorless water (as a control).

The individuals were then shown a square of random color on a screen. They were tasked with adjusting two sliders, one corresponding to the spectrum of yellow to blue and the other from green to red, to turn the color to neutral grey. Each odor was presented five times in random order.

Intriguing results

The study revealed that when certain scents such as coffee were introduced, participants perceived the color grey as having a more red-brown hue than its true shade. Similarly, with the smell of caramel in the air, they perceived a blue-enriched color as grey.

When the smell of peppermint was presented, the participants’ choice of hue was different from the typical crossmodal association demonstrated for the other odors.

Implications and next steps

“These results show that the perception of grey tended towards their anticipated crossmodal correspondences for four out of five scents, namely lemon, caramel, cherry, and coffee,” said Dr. Ward.

“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.”

The researchers emphasized the need to investigate the extent of these crossmodal associations before making conclusions about our sense of smell and color perception.

“We need to know the degree to which odors influence color perception,” said Dr. Ward. “For example, is the effect shown here still present for less commonly encountered odors, or even for odors encountered for the first time?”

The research is published in the journal Frontiers in Psychology.

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