A recent study shows that odors influence human perception of color, with specific odors leading to predictable color associations. Further research is needed to understand the extent of these sensory interactions.
Unconscious associations with smells can distort the perception of color. Our five senses are bombarded with environmental input around the clock. One way our brains make sense of this rich information is by combining information from two or more senses, such as between smell and smoothness of texture, pitch, color and musical dimensions. This sensory integration also allows us to associate warmer foods with warmer colors, lower-pitched foods with lower-pitched foods, and colors with the taste of specific foods—for example, the taste of oranges with the color of the same name.
Now, a recent study published in Frontiers in Psychology experimentally shows that this unconscious "cross-modal" olfactory association affects our perception of color.
Lead author Dr Ryan Ward, senior lecturer at Liverpool John Moores University in the UK, said: "Here we show that the presence of different odors affects human perception of color."
Ward and colleagues tested the presence and strength of the odor-color association in 24 adult men and women aged 20 to 57 years. During the experiment, participants sat in front of a screen in a room with no redundant sensory stimulation. They did not use deodorant or perfume, and none said they were color blind or had an impaired sense of smell.
All ambient odors in the isolation chamber were purified with an air purifier for four minutes. An ultrasonic diffuser was then used to broadcast one of six scents (randomly selected from caramel, cherry, coffee, lemon and mint, plus unscented water as a control) into the room for five minutes.
"In a previous study, we have shown that the smell of caramel often forms cross-modal associations with dark browns and yellows, just like coffee with dark browns and reds, cherries with pinks, reds, and purples, mint with greens and blues, and lemons with yellows, greens, and pinks," explained Ward.
Participants were presented with a screen that displayed a square filled with random colors (with an infinite range of colors), and they were invited to manually adjust two sliders - one from yellow to blue and the other from green to red - to change its color to a neutral gray. After recording your final selection, repeat this process until all scents appear five times.
The results showed that participants had a weak but significant tendency to move one or both sliders too far from a neutral gray. For example, when presented with the smell of coffee, they mistakenly thought "gray" was more like a reddish brown than a true neutral gray. Likewise, when smelling caramel, they incorrectly perceived a blue-rich color as gray. Therefore, the presence of the odor distorted participants' color perception in a predictable way.
An exception was the presentation of the peppermint odor: in this case, participants' choice of hue differed from typical cross-modal associations for other odors. As expected, when presented with the neutral odor of water, participants' choices also matched true gray.
"These results show that for four of the five odorants - lemon, caramel, cherry and coffee - the perception of gray converges towards the expected cross-modal correspondence," Ward said. "This 'overcompensation' suggests that cross-modal associations are powerful enough to influence how we perceive information from different senses when processing sensory input, in this case the association between odor and color."
The researchers emphasize the need to study the far-reaching effects of this cross-modal association between odors and colors: "We need to know the extent to which odors influence color perception. For example, do the effects shown here still hold for less common odors, or even for first exposures?"