Redhead holds blossom
May 12, 2017

Myth busted: Humans actually have a great sense of smell

Humans have long been told that our sense of smell is far inferior to our other senses and that our ability to detect odors and fragrances is light-years behind that of animals such as dogs and rats, but research published this week in the journal Science has revealed otherwise.

In fact, according to study author and Rutgers University neuroscientist John McGann, the belief that humans have a weak, underdeveloped sense of smell when compared to rodents and canines is nothing more than a 19th-century myth perpetuated by a scientist named Paul Broca.

Broca, McGann said in an interview with NPR, “was interested in free will” and “had this idea that smell was this very animalistic sense and that it compelled animals to have sex and feed. And humans, having free will, could choose how we responded to smells and presumably had a less strong or less special sense of smell than other animals.”

A neuroanatomist by trade, Broca’s research suggested that the evolutionary enlargement of the frontal lobe that helped humans develop free will came at the expense of their olfactory systems, which are proportionately smaller than those of other species. However, modern research shows that the human olfactory system is actually quite large when compared to rats and mice (despite the continued erroneous belief that said creatures have superior senses of smell).

“For so long people failed to stop and question this claim, even people who study the sense of smell for a living,” McGann, an associate professor in the Department of Psychology, School of Arts and Sciences at Rutgers’ New Brunswick campus, explained in a statement. “The fact is the sense of smell is just as good in humans as in other mammals, like rodents and dogs.”

People are capable of detecting ‘trillions’ of different odors

McGann has spent the past 14 years studying the human sense of smell, and over the past year, he reviewed much of the existing research on the olfactory system to find the root cause of this long-held belief that people were inferior to other animals when it came to detecting scents.

It was during this time that he found Broca’s work, which he said influenced noted neurologist Sigmund Freud. Building on Broca’s research, Freud argued that atrophy of the olfactory system (later known as “microsmaty”) made individuals increasingly susceptible to mental illness. This theory of microsmaty persisted for much of the 20th century, which caused scientists to overlook research into the olfactory system.

The reality, McGann told Popular Science, is that “most people with a healthy sense of smell can smell almost anything that gets in the nose. In fact, there used to be whole field of trying to find odors that people couldn't smell.” Even though “folk wisdom and poorly sourced introductory psychology textbooks” claimed that humans could only detect about 10,000 unique odors, people can actually discriminate upwards of one trillion smells, he added in a statement.

The truth, the neuroscientist noted, is that the human olfactory bulb – the part of the brain which transmits signals related to the identification of various scents elsewhere – is actually quite large when compared to other species of mammal. With more than 400 smell receptors, McGann said, people are capable of detecting and discriminating “an extraordinary range of odors.” In fact, he wrote, “we are more sensitive than rodents and dogs for some odors.”

-----

Image credit: Thinkstock