What Color Is A Smell? It Depends Where You’re From

Odors are evocative. They can evoke memories, awaken appetite, sexually arouse — and call to mind colors. Those rare few people with synesthesia (the neurological condition in which phenomena are perceived by multiple senses simultaneously) aren't the only ones who associate smells with colors. Neurotypical smellers do, too — and new research indicates that culture trains them to do so.

Researchers designed a study, published last week in the journal PLoS One, to assess if our odor-color associations are learned or if we can chalk them up to universal underlying neurological activity. The study asked 122 participants across six different groups — Dutch, Netherlands-residing Chinese, German, Malay, Malaysian-Chinese, and American — to associate colors with each of 14 different smells. All were healthy, with a “normal” sense of smell (no synesthetes allowed).

Here’s where the experiment got a little like grade school: The smells were delivered to participants by way of pens — “odor pens,” to be precise, loaded with odorant instead of ink. The 14 smells used were ones familiar across cultures, and included “burnt,” “candy,” “fish,” “flower,” “fruity,” “hazelnut,” “meat,” “musty,” “plastic,” “rice,” “soap,” “vegetable,” “vinegar,” and “woody” (a more sophisticated selection than your average Mr. Sketch multipack).

Participants smelled one odor pen at a time, in a random order. Each then selected (from a randomized assortment of swatches) the three colors that the smell most brought to mind, as well as the three that least “matched” the smell. The researchers observed some commonalities across all participants: “Fruity” smells were most commonly linked with reds and pinks, while “musty” smells were linked with oranges and browns.

But, significant differences existed across the groups — indicating that much of odor-color association is indeed culturally driven. Members of the Malay and the Netherlands-residing Chinese groups, for example, were the only ones to associate the smell of “candy” with the color black; U.S. residents were the only ones to associate a “woody” smell with pink. Participants in the U.S.-resident, Malaysian-Chinese, and Malay groups thought of sky blue when they smelled “soap,” but no one else did. Surprisingly, there did not appear to be similarities in the associations made across groups with similar languages. So, red fruit may be an obvious association — but which cultural factors make us think of black candy and pink woods?