- Psychologists and other scientists have paid little attention to humans' sense of smell.
- Olfaction has implications for psychology, ranging from whether a person trust others to how people find their way.
- One study found that sleeping with a romantic partner’s worn t-shirt on a pillow next to them improved women's sleep quality.
- Experiments with lab-grown "noses" suggest humans sense of smell is far more sensitive than that of Neanderthals
When I was in graduate school, there was a period of time when my floor of East Hall (the building housing the psychology department at the University of Michigan) smelled, well ... fishy. Other students and I wondered whether something had broken in the plumbing or the ventilation system. We were told it hadn’t. It was a mystery. It was awful.
What was going on? In fact, one of our fellow students had been running some experiments. Building on the idea that metaphors we use in language can influence our social cognition (Lakoff & Johnson, 1980), Spike Lee had been busy exposing participants to fishy smells (made from a mixture of anchovy and sardine concentrates). What he wanted to test was whether these literally fishy smells would make people more suspicious of others.
In several studies, he found just that. Participants exposed to this scent were less willing to cooperate with others in economic games requiring trust (Lee & Schwarz, 2012). Consistent with the idea that the metaphoric link in English between “fishy” and mistrust was driving these results, participants exposed to a “fart spray” showed no difference in their behavior in these games compared to those in a control condition.
The Nose Knows
What Lee had done was unusual. Social psychologists don’t typically pay much attention to smells. Indeed, you’d be hard-pressed to find a section on scent in a social psychology textbook, or an introductory psychology text for that matter. Yet olfaction has a number of important implications for how we think, feel, and behave.
In a recent review of that evidence, Mark Schaller and his students (Hofer, Chen, & Schaller, 2020) highlight several reasons why it might be worth taking scent seriously in psychological science. First, it turns out that people appear to be able to detect whether someone is sick based on how they smell (Olsson, et al., 2014) and that we tend to avoid individuals whose odors suggest that they are sick (Kavaliers & Choleris, 2017). This suggests that scent may be an important component of the behavioral immune system (Schaller & Park, 2011), an adaptive suite of cognitive, affective, and behavioral responses designed to reduce our odds of acquiring an infectious disease. Yet other work suggests we can also literally smell others’ fear (de Groot & Smeets, 2017).
Others’ odors can also be a comfort to us rather than a signal of danger, as Hofer and colleagues note (2020). In one experiment, researchers found that smelling a romantic partner’s body odor (as opposed to a stranger’s) significantly reduced self-reported stress when waiting to engage in a stressful task, in this case, a mock job interview (Hofer, et al., 2018). In a similar vein, another study found that electric shocks are rated as less painful when people were exposed to their romantic partner’s scent (Gravquist, et al., 2019). Our partners’ smells also help us to sleep better, as suggested by another experiment by Hofer and Chen (2020) which found that sleeping with a romantic partner’s worn t-shirt on a pillow next to them improved sleep quality for women.
Other work suggests, that humans, like a number of other animals, may sometimes be able to navigate by their sense of smell (Porter, et al., 2006). In one of a series of experiments investigating this ability, researchers had participants wear a special outfit (see the picture below) that blocked all sensory cues other than smell. They then tested whether people could a scent path in a field marked by an essential oil derived from chocolate—which undoubtedly was more pleasant than the fish oil described at the beginning of this piece—to see if people, like dogs and rats, might be able to follow their nose, so to speak. Sure enough, the human participants in this study were able to follow the trail and they got better with practice. The researchers replicated this central finding in a series of similar experiments.
For over 100 years, the scientific community has largely dismissed human olfactory capacities. People have been thought to have a sense of smell far inferior to that of other animals (McGann, 2017). Psychology, like many other disciplines, has largely dismissed the importance of human olfaction since the time of Broca (McGann, 2017). Interestingly, our noses may actually be more sensitive that that of some of our early hominid cousins. When scientists grew odor receptors from Neanderthal DNA and compared their sensitivity to those of modern humans, creating lab-grown noses essentially, they found that humans' sense of smell is far more sensitive (Claire, et al., 2023). This fits with what the overall message of the studies we've discussed in today's post; our sense of smell is far from vestigial. In fact, it can keep us safe, give us comfort, and help us to find our way.
Claire, A., Matsunami, H., Abe, M., Cobb, M., & Hoover, K. C. (2023). Genetic and functional odorant receptor variation in the Homo lineage. iScience, 26(1), 105908.
de Groot, J. H., & Smeets, M. A. (2017). Human fear chemosig- naling: Evidence from a meta-analysis. Chemical Senses, 42, 663–673. doi:10.1093/chemse/bjx049
Granqvist, P., Vestbrant, K., Döllinger, L., Liuzza, M. T., Olsson, M. J., Blomkvist, A., & Lundström, J. N. (2019). The scent of security: Odor of romantic partner alters subjective discomfort and autonomic stress responses in an adult attachment-dependent manner. Physiology & Behavior, 198, 144–150. doi:10.1016/j.physbeh.2018.08.024
Hofer, M. K., & Chen, F. S. (2020). The scent of a good night’s sleep: Olfactory cues of a romantic partner increase sleep efficiency. Psychological Science, 4, 449–459. doi:10.1177/0956797620905615
Hofer, M. K., Chen, F. S., & Schaller, M. (2020). What your nose knows: Affective, cognitive, and behavioral responses to the scent of another person. Current Directions in Psychological Science, 29(6), 617-623.
Hofer, M. K., Collins, H. K., Whillans, A. V., & Chen, F. S. (2018). Olfactory cues from romantic partners and strang- ers influence women’s responses to stress. Journal of Personality and Social Psychology, 114, 1–9. doi:10.1037/ pspa0000110
Lakoff, G., & Johnson, M. (1980). The metaphorical structure of the human conceptual system. Cognitive Science, 4(2), 195-208.
Lee, S. W., & Schwarz, N. (2012). Bidirectionality, mediation, and moderation of metaphorical effects: the embodiment of social suspicion and fishy smells. Journal of Personality and Social Psychology, 103(5), 737-749.
Olsson, M. J., Lundström, J. N., Kimball, B. A., Gordon, A. R., Karshikoff, B., Hosseini, N., . . . Lekander, M. (2014). The scent of disease: Human body odor contains an early chemosensory cue of sickness. Psychological Science, 25, 817–823. doi:10.1177/0956797613515681
Porter, J., Craven, B., Khan, R. M., Chang, S. J., Kang, I., Judkewitz, B., ... & Sobel, N. (2007). Mechanisms of scent-tracking in humans. Nature Neuroscience, 10(1), 27-29.
Schaller, M., & Park, J. H. (2011). The behavioral immune system (and why it matters). Current Directions in Psychological Science, 20(2), 99-103.