By Beth Azar
Monitor staff

A whiff of a rapist?s cologne triggers highly emotional memories in a victim. The smell of a lit match conjures up images and desires of getting high for a free-basing heroin addict.

Such clinical anecdotes are partially supported by fairly strong empirical evidence that distinctive odors associated with certain events can elicit memories for those events. But few researchers have examined the link between odors, memories and emotions.

Psychologist Rachel Herz, PhD, of Monell Chemical Senses Center in Philadelphia, is trying to illuminate this connection through a series of studies she?s conducted over the past several years.

?I see this work as a nice way to tie together my interests in emotion and memory,? says Herz. ?It may eventually tie into some grand unified theory of memory, but right now it?s just a very interesting research topic.?

Emotional memories

The connection between odor, memory and emotion has an anatomical basis. The primary olfactory cortex, which receives information about smells from nerves in the nose, links directly to the amygdala, which controls expression and experience of emotion, and the hippocampus, which controls the consolidation of memories.

Odor-evoked memories may seem clearer or more intense than other memories because they appear to be more emotional than memories triggered by visual, audio or other types of cues, Herz finds. While odors don?t help people recall more information, the memories they evoke are more emotionally laden, her research suggests.

In one set of studies, she and University of Toronto psychologist Gerald Cupchik, PhD, studied the ability of undergraduates to recall a series of paintings when cued either with words or with odors. In the study phase of the experiment, each participant saw a series of 16 emotionally evocative paintings. Half the paintings were paired with one of eight odors?including peppermint, iso-amyl acetate and lemon oil?and half were paired with verbal labels of the same odors??peppermint,? ?banana? or ?lemon.?

Two days later, participants returned to the laboratory and, when presented with the same cues they had experienced during the study session they were asked to recall the painting that had been paired with that cue and write a short description of it.

Participants recalled just as many paintings when they were cued with odor labels as when they were cued with actual odors, the researchers found. However, participants rated and described memories of paintings cued by odors as being more emotional than memories cued by verbal labels.

In a follow-up study, Herz found that memories for paintings associated with smells were more emotional than memories associated with touch or vision?the smell of an apple versus the touch or sight of an apple, for example. This makes sense because none of the other senses is as directly or intensely linked to the brain?s emotion and memory centers as smell, says Herz.

Encoded with emotion

Because memories associated with odors seem to be more emotionally loaded, Herz wanted to find out whether odors would be particularly good retrieval cues for memories encoded when a person is in an emotionally charged state.

To test this hypothesis, she examined whether an ambient odor would trigger a better memory for a list of words if a person was emotionally aroused when learning the words.

She gave 40 college students a passive word-learning task: They had to describe an event from their life for each of 16 words presented to them. Herz didn?t tell them they would later need to recall the words. Half the participants conducted the task in a room that was scented with violet leaf?an unusual, somewhat unpleasant odor?and half were in a room with no ambient smell. Also, half of the participants were admittedly anxious because they completed the word task just before an exam. The other participants completed the task on a regular class day.

Herz tested participants? memories of the word list seven days after the incidental learning task. Those who learned the words in the room scented with violet leaf were tested with the smell of violet leaf present.

As seen in other studies, participants who were exposed to the ambient odor during learning and recall remembered more words than participants who were not exposed to the odor. Also, participants who were anxious when they learned the words and had access to the odor cue during learning and recall remembered more words than participants in any other group, scoring an average of 59 percent on the recall test.

People who were anxious and didn?t have an odor cue did the worst, scoring an average of 33 percent. The study appears in the winter issue of the American Journal of Psychology (Vol. 110, No. 4, p. 489?505).

?The basic field of memory, emotion and odors has been largely unexplored,? says memory researcher Eric Eich, PhD, of the University of British Columbia. Herz has done a good job laying down the basic cognitive groundwork of the odor, memory, emotion link. And now he?d like to see the research expanded to include more life-relevant memory tasks, including memory for autobiographical events.

Meanwhile, Herz has begun theorizing about evolutionary explanations for the connection between smell and emotion. Most animals use odors to distinguish between ?good? and ?bad? situations?to let them know when they should approach or avoid food, other animals or specific locations. In humans, this approach-avoid function has primarily shifted over to our emotions, which, as in the fright or flight reaction, we use to evaluate a situation, argues Herz.