Key takeaways
- Young and older adults who completed memory tasks in rooms with lavender essential oil diffused did not perform significantly better than people in unscented rooms.
- Scent improved memory for older adults when encountered at the start of a learning activity but not if encountered later on — and not at all for young adults.
- Scent may be a more effective tool for supporting memory when used strategically, rather than as a general memory booster. The research also suggests that novel sensory experiences may support memory as we age.
The sense of smell shares an intimate but mysterious connection with memory. We know that past experiences can flash vividly to mind if we smell a scent that accompanied them. This has led to claims that aromatherapy can enhance memory or even diminish cognitive decline. But the mechanisms by which the brain associates experience with scent are still being unraveled, and there is mixed scientific evidence to back up such claims.
New research from UCLA suggests the answer is more complicated than you might think. The researchers found that young and older adults who completed memory tasks in rooms with lavender essential oil diffused did not perform significantly better than people in unscented rooms. But there was a catch: Older adults who encountered the scent during the first learning phase performed better than people who encountered it during the second. This suggests that novelty plays a role in binding the scent to experience, especially as we age. Perhaps it's not the type of scent, but the newness of it that boosts memory.
The finding, published in Frontiers in Aging Neuroscience, adds to what scientists are learning about the relationship between the sense of smell and Alzheimer's disease.
"There's been interesting work linking age-related olfactory dysfunction to Alzheimer's disease, which has sparked interest in using changes in olfaction as an early detection tool," said UCLA neuroscientist and corresponding author Stephanie Leal. "We designed our study to think about how olfactory cues might be able to modify memory in the context of olfactory dysfunction."
Leal and colleagues at Rice University recruited young and older volunteers, all of whom were healthy and had no signs of Alzheimer's. They used a standard olfaction test to establish baseline olfactory functioning. Half the participants entered a room already scented by a lavender essential oil diffuser. Lavender was chosen because it is a common scent many people are already familiar with and may find pleasant or unpleasant. The other half entered an unscented room. The volunteers then looked at two sets of images of everyday household objects on a computer screen, such as a blow dryer or tomato, that varied in the number of overlapping features they had. Participants who viewed the first block in the odor condition viewed the second block of images in the non-odor condition, and vice versa.
What the recall phase revealed
After a delay, the researchers showed participants images that were identical to, slightly different from, or entirely different from the ones they had previously seen. During this recall portion of the experiment, many of the objects were slightly altered. For instance, a blow dryer that was red in the learning phase was blue in the recall phase, and participants had to remember whether they had seen the object before but also whether it was identical to the image they had previously viewed. This was designed to test general recall — the memory of seeing a type of object — as well as detail memory, such as the object's color. They also asked other questions, such as how pleasant participants found the scent.
"When we looked at general and detail memory measures, older adults struggled to remember the details, which we expected," Leal said. "Interestingly, the presence or absence of odor made no difference for older or younger adults. We were kind of scratching our heads because that was surprising based on prior work that showed olfaction might enhance memory."
However, the order in which older participants encountered the scent mattered. Older adults who smelled the lavender scent during the first learning phase recalled the objects more accurately than those who encountered the scent in the second learning phase. There was no difference for younger adults.
Older adults who found the scent pleasant and those who had less olfactory dysfunction to begin with showed better detail memory.
"If we want to support memory in older adults, we need to think beyond simply whether a stimulus helps or hurts memory and consider when and how it is experienced," Leal said. "A big component of learning in aging is novelty. Engaging in learning in an enriched context may make it easier to learn new things."
Overall, the findings suggest that scent may be a more effective tool for supporting memory when used strategically, rather than as a general memory booster. They also highlight the potential importance of novel sensory experiences in supporting memory as we age.
The researchers involved in this project were funded by the National Science Foundation, the BrightFocus Foundation, the Brain and Behavior Research Foundation, and the Alzheimer's Association.
