by Marjorie Prokosch, Zachary Airington, and Damian Murray
Our sense of smell helps us to make sense of the world. Our mornings can be improved by smelling a cup of coffee; our nose tells us which foods in the fridge may have turned; the smell of a loved one’s worn shirt transports us to the emotions of that relationship. However, despite how daily experiences are influenced by smell, relatively little research has examined how smell guides human social cognition and behavior.
Previous research points to two social processes in which our sense of smell is especially important: 1) deciding with whom we should form and maintain close relationships, and 2) helping us to avoid things and people that could make us sick. People rate smell as being an important factor in romantic partner choice, and tend to find the smells of a romantic partner to be more comforting and attractive than the scents of others. People also tend to be disgusted by and avoid the sources of foul, disease-connoting odors (like the body odors of sick people). New research is now beginning to examine how individual differences in how well we smell might also shape these processes.
In a recent study, we explored how smelling ability, disease avoidance, and one aspect of close relationships—mating strategy—are related. Here, by mating strategy we refer to people’s interest and participation in monogamous romantic relationships (long-term mating strategy) and short-term sexual relationships (short-term mating strategy). We predicted that smell ability would relate to people’s trait disease avoidance and mating strategies. For example, people who can more easily detect smell-related disease threats might tend to be more disease avoidant. Further, people with greater ability to smell relevant cues of quality or compatibility in potential partners (or, proximally, who might be more easily disgusted by unfamiliar body odors) might be less inclined to engage in short-term sexual relationships. Past research has also found that people high in disease– and sex– related disgust are less inclined to engage in short-term sexual relationships, so we expected to find a similar link in our study, too.
To measure smell ability, we tested participants with Sniffin’ Sticks—a battery commonly used in clinical smell research. The Sniffin’ Sticks test measures three facets of smell ability: threshold, discrimination, and identification.
Threshold is the ability to detect scents. Participants smelled groups of pens where two were unscented and one contained a concentration of n-butanol, which has an alcohol-like smell. Participants with a more sensitive smell threshold could correctly pick out weaker concentrations of n-butanol. Discrimination is the ability to tell scents apart from one another. Participants smelled groups of pens where two pens contained one scent and a third pen contained a different scent. Participants who were more discriminating correctly picked out more of the uniquely scented pens across trials. Identification measures the ability to recognize and name specific odors. Participants smelled a set of common scents (e.g., leather, fish, banana). Participants with greater identification ability could correctly name more of those scents. In total, the test takes about 45 minutes to administer. Participants then completed surveys assessing their interest in short and long-term mating strategies, their dispositional sexual and disease-related disgust, and how chronically vulnerable to diseases they felt.
We found that smell discrimination–people’s ability to tell smells apart from one another—was related to people’s interest in short-term mating, such that people who were better at telling smells apart tended to report less comfort with engaging in short-term, sexual relationships. People with greater smell discrimination also tended to report more disgust towards potentially unpleasant sexual scenarios (such as hearing others have sex). These relationships remained consistent after accounting for other factors that could meaningfully impact performance such as gender, English proficiency, and recent sickness (and after adjusting our false positive rate to account for performing multiple tests).
We found that smell discrimination–people’s ability to tell smells apart from one another—was related to people’s interest in short-term mating, such that people who were better at telling smells apart tended to report less comfort with engaging in short-term, sexual relationships.
Interestingly, we did not find a link between people’s smell discrimination abilities and their disease avoidance tendencies (disgust towards the germ-rich situations, feelings of vulnerability). Superficially, this is inconsistent with past theorizing about smell ability and disease avoidance. Smell threshold and identification abilities did not consistently relate to any of our survey measures. Why might this be the case? It is possible that there are really no relationships of interest between threshold, identification, and mating or disease avoidance. However, it’s also possible that aspects of our testing procedure, like the scents or survey measures we used, interfered with our ability to detect small but meaningful relationships.
Our results leave lingering questions for future work. Why is the ability to tell different scents apart relevant to discomfort with short-term mating situations and strategies? It’s possible that when evaluating potential partners, the ability to discriminate between different scent cues of “good partner fit” is more important than the ability to detect these cues, per se. People especially sensitive to different scent cue combinations that signal “bad partner fit” might in turn, have a dampened desire to pursue mating strategies that emphasize casual sex. We also do not know which specific scent cues might be important for determining “good” or “bad” partner fit. Scents related to health, immune compatibility, or fertility may be worth investigating.
Another question is whether (or how) specific smelling abilities actually factor into established, long-term relationships. Although our data didn’t imply that smell sensitivity influenced actual relationship status, smell ability may still be important for forming and maintaining long-term, romantic partnerships. For example, some research does suggest that smell is related to sexual satisfaction. Specific smell abilities may play a role in aspects of long-term mating strategies that we didn’t measure in our study.
In sum, does the nose know? Our research suggests, maybe. At least, our ability to detect differences in odor cues seems to be related to our comfort with short-term mating.