“A vanilla-like aroma” does not refer to a single material that produces that impression. Even when aromas receive similar ratings for intensity and pleasantness, does the brain process them in the same way?
In 2025, Akshita Joshi and colleagues asked 44 people to smell three vanilla-like substances and compared their ratings with brain responses measured by fMRI. Could subtle differences between similar aromas be detected through brain activity? The study focused particularly on the feeling of “knowing” an aroma and on processing related to memory.
The Same People Smell Three Vanilla-Like Odorants
The substances compared were vanillin, vanitrope, and vanillyl ethyl ether (VEE). All have vanilla-like characteristics, but they are distinct chemicals. The study did not compare vanilla pods themselves or commercial vanilla perfumes.
The participants were 44 healthy adults with a normal sense of smell confirmed by olfactory testing, with a mean age of approximately 27 years. A separate pilot study involving 15 people assessed whether the three aromas to be presented were similar in intensity.
In the main experiment, a device delivered temperature- and humidity-controlled air to both nostrils. Each person underwent three measurement sessions, with one aroma presented in each. Periods with and without odor alternated, and the order in which the aromas were presented was also controlled.
Participants rated aroma intensity, pleasantness, and familiarity. At the same time, fMRI captured responses related to brain activity through changes in blood oxygenation. The images do not show the thought “I remembered vanilla” itself, but rather brain responses while receiving the aroma.
Participants’ Ratings Showed No Clear Differences
There were no statistically clear differences between the three aromas in ratings of intensity, pleasantness, or familiarity. For example, mean familiarity ratings on a 0–10 scale were similar: 4.07 for vanillin, 3.86 for vanitrope, and 3.95 for VEE.
However, similarity on these three measures does not mean that the aromas were identical in quality. The experiment did not directly measure behavioral discrimination, such as correctly identifying the three aromas when presented together or picking out the different one.
Differences Between Aromas Were Reported in Some Brain Regions
The brain images showed areas responding to all three aromas, as well as areas where responses differed by aroma. In the whole-brain analysis, vanillin produced a stronger response in the left amygdala than vanitrope or VEE. A difference in the right parahippocampal gyrus was also reported in the comparison with vanitrope.
An additional analysis comparing responses in selected brain regions found a difference between vanillin and VEE in the right hippocampus. However, differences between aromas were not clear in many of the regions examined. The results did not show that the entire brain responded in completely different ways to each aroma.
Exploratory analysis of relationships with familiarity ratings also found relatively weak correlations. Participants who rated vanillin as more familiar tended to show a larger response in the right orbitofrontal cortex. For vanitrope, higher familiarity ratings were associated with a smaller response in the right hippocampus. These are correlations, not results establishing familiarity as the cause of changes in brain activity.
How Far Can the Links with Memory and Emotion Be Taken?
The authors suggest that the amygdala, regions around the hippocampus, and the orbitofrontal cortex may participate in processing that connects aroma with emotion, memory, and judgments of familiarity. Their interpretation is that exposure to vanillin through various foods and scented products may have linked it more readily than the other two substances to experiences of “familiar vanilla.”
However, the familiarity ratings in this study showed no clear difference indicating that vanillin was more familiar than the other two. Nor did the researchers measure whether a specific memory came to mind, whether a memory persisted until a later day, or whether memory ability improved. Activation of memory-related regions alone does not demonstrate those effects.
The original paper’s account of its analyses also warrants caution. Although the same people experienced all three aromas, some comparisons are described as using tests for independent groups, and there are inconsistencies between the stated analysis criteria and numbers in the tables. The reliability of the reported differences needs to be assessed through clarification of the analyses and replication, among other steps.
The study was supported by Takasago, and coauthor Jonathan Warr is affiliated with the company and contributed to the study’s conception and manuscript revision. The authors declare no conflicts of interest. The study examined responses at specific concentrations and under specific presentation conditions; it did not compare perfume liking, purchasing behavior, or health benefits.
Summary
Even though the three vanilla-like odorants received similar ratings for intensity, pleasantness, and familiarity, different responses were reported in some brain regions. The authors consider fMRI a potential way to investigate the processing of similar aromas that simple ratings may not fully capture.
It is important not to equate differences in brain activity with conscious aroma discrimination or improvements in memory. These findings offer clues for investigating aroma similarity in relation to past experience and emotion. More detailed patterns of brain activity and relationships between regions need to be examined to establish how similar aromas are processed differently.
References
Joshi, A., Thaploo, D., Weise, S., Warr, J., & Hummel, T. (2025). Cerebral Insights Into Discrimination of Perceptually Familiar Odours: Vanillin, Vanitrope and Vanillyl Ethyl Ether. Flavour and Fragrance Journal, 40, 937–945. DOI: 10.1002/ffj.70005 / Full original article.
Original article license: CC BY. © 2025 The Author(s). Flavour and Fragrance Journal published by John Wiley & Sons Ltd.
