Do You Smell That?

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You know those people who can always smell something?

• Do you smell that?
• That smells musty.
• This chicken has a funny smell to it.
• This thing smells like rotten milk.
• Gross! You really can’t smell that?!

In a recent study conducted at Tulane University, researchers Zachary Airington, Marjorie Prokosch, and Damian Murray (2019) tried to illuminate the evolved psychology of these “super smellers.”

The Evolutionary Psychology of Disgust

Think about something that disgusts you. Feces on the sidewalk? Vomit? A creepy guy who smells vile and who won’t leave you alone in a social setting? Take your pick.

As is true of emotions writ large, disgust evolved to help us avoid stimuli that would have had adverse survival or reproductive-relevant consequences for humans under ancestral conditions (and, likely, now as well). Our ancestors who stopped eating when someone vomited at the dinner table were less like to ingest dangerous pathogens that might have made it onto their own food. An ancestral woman who made a point to effectively reject the advances of a disgusting, creepy guy would have been more likely to mate and bear offspring with someone of higher mate value. And so forth. Disgust is a part of our “behavioral immune system,” and it evolved to facilitate survival and reproduction. Disgust acts as a classic behavioral adaptation.

Disgust, Smell, and Evolution

In Airinger et al.’s research, they essentially argue that olfactory ability evolved to help us navigate a world that is partly peppered with disgusting stimuli—stimuli that could have adverse consequences pertaining to survival and reproduction.

The nature of our olfactory system, then, evolved for a function.

Individual Differences in Olfaction Abilities

As is true of many behavioral adaptations, olfaction ability is not completely uniform across people. Some people have a better sense of smell than others do. The team from Tulane set out to figure out why this is the case.

Generally, these researchers predicted that increased olfactory acuity would tend to correspond to (a) markers of disgust sensitivity and (b) approach to sexual interactions. In short, they predicted that people with highly attuned olfaction abilities would be relatively sensitive to disgusting stimuli and that they would, generally speaking, show a preference for relatively long-term (monogamous) mating rather than short-term, promiscuous mating. In short, these researchers predicted that heightened olfaction ability serves a special function in some people: It allows them to be particularly sensitive to disgusting stimuli, and it encourages them to utilize a relatively low-risk approach to intimate relationships.

In a sample of nearly 200 young adults, the researchers found general support for their basic predictions. They found that super smellers (a) showed more sexually specific disgust sensitivity and (b) showed a relatively low inclination toward short-term mating interest.

Super Smelling as Vigilance

At the NorthEastern Evolutionary Psychology Society conference, I was fortunate to have a conversation with the study’s lead author, Zachary Airington—who, by the way, won the NEEPS conference’s award for the Best Student Poster for this work. Congrats, Zachary! I suggested that a broader explanation for this set of results may be found in the psychology of hypervigilance (or being super-attuned to stimuli in one’s environment). Here, I spell out that reasoning.

Hypervigilance is characterized by someone being especially sensitive to the stimuli that surround him or her. A pen drops across the room, and the hypervigilant person immediately stands up and orients toward that part of the room. Someone across a crowded room looks briefly in this person’s direction, and the hypervigilant person focuses keenly on this glance, immediately working to infer why that person just stared at him or her.

While hypervigilance has several causes, one well-known cause is found as a response to trauma, vis a vis this 2005 report of the National Collaborating Centre for Mental Health (UK). People who have experienced traumatic events have learned through such experiences that life can be dangerous and that people are not necessarily to be trusted. Hypervigilance, then, can be seen as a specific adaptation that follows from such experiences. If life is truly dangerous based on what has happened to you in the past, it likely pays to be hypervigilant at all times.

Being a super smeller may well be a psychophysiological facet of hypervigilance. Perhaps people who have had some experience with trauma have relatively highly attuned olfactory abilities. Perhaps they are more sensitive to disgusting stimuli, because in their actual experiences, they have encountered survival-threatening disgusting stimuli. Perhaps they are wary of short-term, promiscuous mating situations, because they have been interpersonally burned in the past and, thus, have their evolved psychological guard up.

Being wary of trusting others for short-term intimate relationships, having particularly highly attuned olfactory ability, and being easily disgusted, then, may be part of some broader adaptive response to adverse life experiences. (Looking for a research idea in the evolutionary behavioral sciences? I’d love to see someone design and carry out a study to predict the model that I propose herein!)

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Bottom Line

Some people can literally smell various stimuli better than others can. Zachary Airington and his team from Tulane set to figure out why this is the case. Based on their data, it looks like super smellers have relatively high disgust sensitivity (particularly vis a vis sexual stimuli), and they tend to be hesitant to seek short-term mating opportunities.

Is this all, perhaps, part of some broader hypervigilance adaptation? Is it part of some unconscious strategy that serves to have those who have had highly adverse experiences be on the lookout for danger? Only future research will tell.

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