In an experiment that involved computer games and custom-made scents, researchers found that responses to new odors depended on emotions experienced while the new odor was present. If participants had a good time playing the game, they were more likely to report liking the odor they smelled. If they had an unpleasant experience, they were more likely to dislike the scent.
"As humans, we're not immediately predisposed to respond to a scent and believe that it is good or bad," said Rachel Herz, a visiting assistant professor of psychology at Brown and the lead scientist of the study. "When we like or don't like a smell, that is learned."
Herz conducted two experiments to test her theory of olfaction. The first included 30 female participants. All were asked to smell five scents, infused in cotton in glass jars, and rate them on a 9-point scale for pleasantness, familiarity and intensity. Most odors were familiar and pleasant - rose, vanilla, lemon and peppermint. But one was new: a unique mix of odors that included dirt, rain and hot buttered popcorn. The result was a sweet, dank, slightly unpleasant scent.
Participants were randomly assigned into groups. The experimental group entered a room where the new scent was dispersed in the air by a hidden machine. Then they played a card game on a computer. The game was rigged for fun, using humorous sound effects and smiling faces. This same group, in a later session, was shown a compilation of scenes from the comedy "Something About Mary." Again, the strange scent was gently piped into the room.
Three control groups were used. The first group also played the game and watched the film, but no smell was present. The second group was exposed to the scent but watched neutral nature documentaries during both sessions. The third sat in an odorless waiting room with different magazines during the sessions.
The second experiment was similar, but it included 36 participants, both men and women, and tested two new scents. One was slightly floral. The other had a clean, watery smell. All participants rated these scents - as well as rose, vanilla, lemon and peppermint - in a pretest. Participants rated the new scents as both unfamiliar and pleasant.
Then one group entered a scented room and played a computer card game designed to be frustrating. The sound effects were annoying and it dealt losing hands. The second group sat in a scented room and read magazines. In both groups, half were exposed to the floral scent, the other half to the watery one. The third group played the computer game in an odorless room. All participants either played the computer game or read magazines in three sessions spread out over the course of a week. After each session, they rated the six scents.
The results: In the first experiment, Herz found participants who played the game and watched the film clips were more likely to rate the new odor - even though it was slightly unpleasant - as enjoyable and familiar compared with control groups. Results were similar in the second experiment. After playing the frustrating game, participants were more likely than control groups to score the pleasing new odors as distasteful - a negative association that grew over time.
Bottom line: When an odor is paired with an emotional event, perception of that odor was altered to fit that association.
Herz wasn't surprised. Little rigorous data exists, Herz said, to back a genetic theory of odor and perception. Herz said cultural studies of olfaction also back her results. Americans, for example, tend to like the smell of wintergreen, a common ingredient in candy and gum. Yet in Britain, where wintergreen is often used to make medicine, the odor is less pleasing.
"We can see that this is true from personal experience, as well," Herz said. "Some people may smell a rose and be reminded of their father's funeral. Others may like the smell of skunk because they have a positive attachment to it from childhood."
Herz said there are a few exceptions to this theory. Irritating odors, such as ammonia, may be immediately disliked when smelled. Individual genetic differences may also play a role in emotional responses to odors.
Herz said the study adds to science's mounting understanding of olfaction. Results, however, may also be of interest to marketers. Herz said retailers and restaurateurs want to offer a pleasant experience. A small but growing group, Herz said, use signature scents to create a positive association with consumers. "Using odor to improve mood has industrial applications," she said. "Scent could even be used in schools or hospitals to improve performance or speed recovery."
Herz conducted the experiments with the assistance of Sophia Beland, a former research assistant at Brown, and Margaret Hellerstein, a former Brown undergraduate.
Oakland Innovation, a British consulting firm, funded the research.