Science / Medicine : Do Smells Trigger Memories?

Scientists have known for some time that mood has an impact on what we remember. Now, two psychologists say they have found that odors affect people in much the same way.

Do pleasant smells--Bazooka bubble gum, popcorn, roses or apple pie--trigger happy memories?

Human experience suggests yes. But psychologists at City University of New York have set out to prove this ubiquitous experience in the laboratory. Indeed, they did find that pleasant odors are more likely to stimulate happy recollections; foul odors, unpleasant ones.

Such findings indicate that odors direct the human mind into certain paths of thinking. If so, the implications are unlimited. Companies could send wafts of peppermint through the air-conditioning system to stimulate workers to produce more. Scent vials could be carried around to adjust moods, akin to the practices of 19th-Century Chinese.

According to Trygg Engen, a researcher at Brown University, odor perceptions “re-create significant past episodes in a person’s life. . . . The strength of memory varies with the special involvement a person has with the odor.”

His studies on remembering odors appear in a recent issue of American Scientist magazine.

Engen and others believe that odors and memories are intimately related because the olfactory bulbs, where smell is processed, have a direct connection to brain areas involved in memory--the amygdala and hippocampus--and mood--the limbic system. Other sense impulses travel a circuitous route to these areas.

Connection Long Known

Scientists have known for some time that mood can have an impact on all kinds of things that people remember. Now, psychologists Howard Ehrlichman and Jack Halpern say they have found that odors can affect people in much the same way that mood can.

The CCNY researchers tested dozens of odors to come up with mixtures people think are pleasant. They settled on almond extract. For an unpleasant odor, they picked malodorous pyridine, a chemical that smells rancid.

Ninety college women took part in the study. Memories were elicited in response to neutral words (like table ) in the presence of either a pleasant odor, an unpleasant one, or with no odor present at all. At the end of the experiment, the odor was removed, and subjects were asked to rate their memories on a scale of happy to sad.

The researchers found that subjects exposed to the pleasant odor had far more positive memories than those who sniffed the pyridine.

But how specific are these effects? Is the odor altering mood, which in turn sways memory? Would smells that elicit sad moods prime memories for other negative emotions such as fear and anger? Are smells specific to certain mood states?

These questions have fueled the growing interest in odor memory. At the University of New Hampshire, Robert Mair, assistant professor of psychology, has found that amnesic patients, some of whom have lost all memories, have an inability to distinguish odors. Indeed, people with Korsakoff’s psychosis, a memory loss often seen in chronic alcoholics, have both memory and odor problems.

Mair has found that both groups of patients he studied lacked normal amounts of a brain chemical called norepinephrine. This may be the chemical key researchers have been looking for, he said. Deficits of this substance may be responsible for patients’ poor memory, including odor recall.

Can’t Name Odors

Interestingly, Brown University’s Engen has found that people have a difficult time naming odors, the tip-of-the-nose phenomenon.

“You give someone an odor, and they might offer a general category but can’t get more precise than that,” Engen explained. He suspects that it has something to do with the fact that both memory and odor are tied into the more primitive areas of the brain. Odors trigger emotions, not words.

“In the tip-of-the-nose state, the person appears to have no verbal information about odor names,” Engen said. In one test, he had people simply name odors spontaneously. Some people were given “brand names” like Ivory soap, Vick’s Vaporub and Bazooka bubble gum, to smell. Other odors were grape, smoke, mint, gasoline and licorice.

Subjects tested on brand-name odors responded correctly on average 44% of the time. The other odors, presented to the subjects on scratch-and-sniff cards, were slightly more difficult to detect. Subjects did worse than if they had been guessing by chance, about 32%. Women did better than men in both test situations.

In another study, multiple-choice options were given to people asked to name a particular smell. In the group where the alternatives were far afield from the real odor--for example, pizza, turpentine, grape and clove--subjects answered correctly 93% of the time. If the choices were lumped in a category--like melon, plum, grape, strawberry--subjects did no better than chance.

“Odor memory is largely limited to recognition,” Engen said. “The main function of the sense of smell is not to recall odors for cognitive reasons but to respond to the odors actually encountered,” he wrote in American Scientist.

It is no wonder that Craig B. Warren, director of the taste and smell laboratory at International Flavors and Fragrances, considers perfume to be “psychology in a bottle.”

Warren, a chemist, explained that fragrance is a strong conditioner, serving as a cue to memory. “Memory is triggered when someone has an intense emotional experience in the presence of an odor,” he said.

Warren works specifically on how odors stimulate mood and emotion. The company has been doing research on mood mapping, taking various flavors and fragrances and seeing whether they alter mood: Subjects are exposed to an odor and then use an adjective checklist to rate how they feel.

In collaboration with researchers at Yale University, the lab’s researchers have found a number of fragrances that stimulate the subjects or help them relax. While these chemical potions are not yet patented, he can only hint at the preparations. For example, an orange-like odor has been found to bring on relaxation; lavender is stimulating.

“At the moment, perfumers use intuition in creating fragrances,” Warren said. He calls it perfumer’s art, likening the skill to that of a painter. “The real craft comes when they create odors that are not found in nature.” He suspects that odor is mediated directly by the limbic system, the area of the brain associated with moods and emotions. The limbic system is also the seat of all sexual arousal. “We find few (commercial) fragrances that stimulate without being sensuous, suggesting that you are getting a limbic response,” Warren said.

After doing mood experiments on hundreds of compounds, the researchers agreed that spiced apple helps reduce stress. The company just received a patent on the compound.

Experiment Described

Their test subjects were given a mental exercise known to induce a stress response, counting forward by factors of seven. The task stressed subjects and elevated their blood pressure. The subjects were then given spiced apple to smell. It not only blocked the stress response, but lowered blood pressure. In tests conducted on 40 Yale students, the researchers also measured brain waves of students when they were given different fragrances.

The apple-spice fragrance helped stop panic attacks and reduce stress in some people, the researchers said. Certain fragrances were most effective in particular situations. For example, a lavender odor kept drivers alert behind the wheel of a car.

“Smelling or even imagining food induces changes in brain waves that are very similar to those we find during relaxation therapy when we ask patients to concentrate on breathing deeply and slowly while they envision themselves sinking down into a comfortable chair,” Yale’s Tyler Lorig, an associate research scientist in psychology, said. Lorig and colleague Gary Schwartz made the discovery during a five-year study funded by International Flavors.