Paul Broca, a French brain researcher in the 19th century, hypothesized that humans evolved to trade in our "bestial sense" of smell for higher brain capacity.

Smell retraining can help people with anosmia learn to smell again

Olfactory training, which involves repeatedly smelling a selection of strong odors, teaches your brain to familiarize itself with experiencing smells over a lengthy period, typically multiple months. This can be useful for patients who lose their sense of smell for myriad reasons.

Olfactory training, a widely recommended treatment for people with long-term loss of smell after a viral infection like COVID, can be performed at home using bottles of essential oils—often lemon, rose, clove, and eucalyptus—to help reorganize neural connections in the brain.

A stand-in 'nose' may help people with anosmia to smell certain odors

In a 2025 paper, researchers reported they'd created a proof-of-concept device that bypasses typical olfactory pathways and instead exploits an alternative—the trigeminal nerve in the nose—to detect a few strong scents. The nerve typically helps detect the temperature of inhaled air or the presence of irritants. (Some users may experience a paywall.)

Humans can't smell the inside of their nose due to olfactory fatigue

Once a person is accustomed to a specific odor, their neurons have trouble continuing to respond to that smell because of that familiarity. That's why humans may not notice when their house smells like trash until they leave the house and then return to it.

Our sense of smell affects what foods taste like and how we perceive it

Scent stimulates our olfactory sensor neurons high in the nasal cavity, and the brain attaches labels to those scents. But when we eat, chemicals from the foods travel from our mouths and throat to those neurons. We have roughly 400 odor receptors, and they can be used to decipher more than 10,000 different odors (or more than one trillion by some calculations), including the nuances of different foods.

Loss of sense of smell is a common symptom of COVID-19 infection

In 2020, researchers discovered why this occurs. The virus that causes this infection attacks the cells that support smell-detecting neurons. Once infection clears, the sense of smell typically returns, though the exact timeline for that differs by patient. (Some users may experience a paywall.)

Read the academic article explaining how ancient smells can be dissected and recreated

This paper explores how biomolecular data on past scents can be teased out and then transformed into olfactory museum experiences, adding another component to our understanding of archaeology.

Humans can track smells on the ground quite well—our ability to crawl is a limiting factor

As part of a scientific bet, neurobiology researchers dragged a chocolate bar across the grass and sought to see if a human could track it—she could. This led to a more in-depth experiment on human olfactory capabilities and behavior when other senses were blocked.

Humans may be able to distinguish more than one trillion scents

That's according to one estimate published in 2014. This figure far exceeds earlier estimates of a human smelling ceiling around 10,000 odors. The newer figure is derived from experiments in which volunteers agreed to sniff varying scents. Researchers mixed odor components and had volunteers sniff the brews to detect subtle scent differences. (Some users may experience a paywall.)

Anosmia is the total loss of the sense of smell

This type of loss—due to disease or trauma—has ripple effects, including an altered or limited sense of taste. This video details the anatomy and physiology of our sense of smell and taste and how these senses are interrelated.

Smell is a robust memory cue for individuals with Alzheimer's disease

Odor is more effective than both visual and verbal cues for triggering autobiographical recall in Alzheimer's disease, according to 2021 research.

Scent is a stronger memory trigger than sight

Smell is imbued with more emotion than visual memories, and research indicates that smell triggers a significantly greater effect on amygdala activation. Scientists believe these powerful responses occur partly because smell signals bypass the thalamus and go directly to the amygdala and hippocampus, brain areas involved in emotion and memory.

Roughly 15 of every 1,000 people in the US have smell disorders

Anosmia is a lack of a sense of smell. It can be present at birth, related to diseases including Parkinson's, Alzheimer's, and COVID-19, or have unknown causes.

Newborns have a strong sense of smell

Babies are drawn to their mother's smell—and the particular odor of their mother's breast milk—within days, even as their vision remains blurry for months after birth. In the womb, the olfactory center also forms in the early stages of development.

Scientists are reconstructing ancient smells—including a 3,500-year-old ancient Egyptian mummy

Researchers explain how they have recreated the scent of ancient Egyptian mummies and enabled museum-goers to experience that scent on specialized cards. The exhibit will be at the Royal BC Museum in Canada in June 2026.

A dog's central sniffing organ is many times bigger than a human's

The olfactory epithelium, located high up within the human nose, is home to millions of olfactory neurons. A dog's olfactory epithelium is much larger—and has more neurons—than a human's, which helps to explain the animal's superior sniffing ability.

1 in 15 adults over age 40 experience phantom odors

This phenomenon was measured in a 2018 study that examined the prevalence and risk factors for phantom odor perception. Older adults were less likely to experience these phantom odors as they age, just as their overall sense of smell declines. Women are more likely than men to perceive phantom odors.

Hereditary hyperosmia is the official term for being a super-smeller

Some sniffers with this rare trait may be more sensitive to pleasant smells, while others may be more attuned to unpleasant scents. Some research suggests that certain genetic mutations are associated with a heightened sense of smell.

Efforts to create disease-sniffing capabilities for phones still can't match dogs

In this video, a scientist explains why dogs remain leaders in olfactory capabilities, outpacing technology. Scientists have attempted to create artificial "e-noses" for phones to detect early signs of disease, but so far they have not been successful.

Read a study documenting how 'old people' smell increases with age

Analysis of body odors from individuals aged 26 to 75 confirmed that 2-nonenal, an unsaturated aldehyde with an unpleasant, greasy, and grassy odor, was detected only in subjects aged 40 and older.

A super-sniffer smelled her husband's Parkinson's disease years ahead of symptoms.

Heightened sense of smell during pregnancy is not yet well understood

Boosted smell powers and strong reactions to them are often reported beginning around the six-week mark of pregnancy. Researchers say hormonal changes likely play a role, but the change remains poorly understood.

How our sense of taste evolves as we age

Kids are hardwired to prefer sweets over greens, with sweetness a shorthand for calorie-rich and bitter flavor warning of potentially noxious plants. This holds true even in the womb, where fetuses have been seen via ultrasound scans grimacing as their hosts consume kale capsules. As they age into double digits and beyond, their taste cells and sense of smell diminish, leading to broader and less sensitive palates.

If hearing is damaged, the brain may amplify remaining sounds, perhaps causing tinnitus

Recent mouse brain and ear imaging revealed that the creature compensates for hearing loss by sending signals to the cochlea in the inner ear. This triggers nerve fibers in the inner ear to increase volume and become more sensitive. Learning about these boosted-sensitivity messages from the brain to the cochlea—if they're similar in humans—might help explain tinnitus and fuel experimental approaches to turn down that sensitivity.

Corynebacterium species are particularly responsible for our funky smell

Myriad bacteria contribute to our body odor, but research suggests that Corynebacterium species are strongly associated with the bad smells emanating from adults. Staphylococcus and Cutibacterium genera may also play leading roles.

On average, people smell worse if they're sick

For a small 2014 research study, a panel was tasked with sniffing the smelly t-shirts of people who had been injected with a compound known to activate the immune system and those of controls without the shot. It found that those who were acting as if unwell (due to the injection) generally smelled worse. Subsequent work found that those who sniffed unpleasant odors had a mild immune response of their own—perhaps to protect them from disease. (Some users may experience a paywall.)

The importance of volatile aroma compounds in the flavor quality of food

Processes such as air movement and heating cause food to lose aroma molecules, which studies have shown play a major role in our sense of taste. While losing these molecules to the environment leaves fewer to be processed during consumption to intensify flavor, it can also produce previously nonexistent aroma compounds or release previously trapped ones, altering or enhancing the food's flavor.

'Old people' smell is real—it's a chemical buildup when fatty acids on the skin oxidize

The chemical composition of body odor seems to change with age. Later in life, we harbor higher concentrations of a chemical compound called 2-nonenal that forms when omega-7 fatty acids on the skin oxidize, and the skin's natural antioxidant defenses weaken. Commonly called "nonenal", it's the smell widely associated with aging, and it's often described as a grassy or greasy odor.

The evolution of the human brain

The human brain, in all its staggering complexity, is the product of millions of years of evolution. Read on to find out about brain size and intelligence, language and brain development, and more.

The role of fire in the evolution of humanity's big brains

Roughly 1.5 million years ago, the brain size of our hominin ancestors exploded. To understand why, Richard Wrangham posited the cooking hypothesis, arguing the adoption of fire as a means to cook food had a lasting impact on our ability to digest...

Patient H.M. revealed that the hippocampus was responsible for memory formation

Henry Molaison became a landmark case in psychology after surgery removed large portions of his hippocampus, leaving him unable to form new memories. Upon his death, Molaison's brain was sliced into 2,401 sections and digitized for research.

Carboxylic acids are one reason teens are smelly

Scientists compared the smells of babies and teenagers and identified some of the compounds that make teens smelly. Carboxylic acids present in teens, they wrote, seemed to give off an "earthy, musty, or cheesy" scent. This 2024 research could help inform future odor-control products.

Using brain implants to restore vision

Several companies are attempting to create brain-computer interfaces that skip over retinas and optic nerves to allow visual input to go straight to the brain, potentially restoring some sight to the blind. Clinical trial findings suggest restored sight is sparse and manifests differently than a sighted person might expect, appearing as specks of "light" clusters called phosphenes to help differentiate one's surroundings.

How does the body know where it is in space?

Close your eyes and touch your nose. How did you know where your nose was? How could you tell where your hand was? That's proprioception, the sense that keeps your brain apprised of the body's position and movement. This article explains how this sense works, what happens when people don't have it, and what we know about it.

The 'sense' of direction comes from two strategies involving unique brain regions

Egocentric navigation utilizes the caudate nucleus and posterior parietal cortex, relying on a person's position in space to determine their direction of movement. Spatial navigation uses landscape features for orientation and is driven by the hippocampus.

Psychoactive drugs found in 1,000-year-old bag made of fox noses

Archaeologists in Bolivia have uncovered an ancient bag filled with "amazing goodies" that suggests the owner or owners were well-versed in the properties of psychoactive substances and sourced goods from well-established trade routes. This article details the findings, which shed light on how ancient peoples in the region consumed and obtained psychoactive substances.

Mosquitoes even have olfactory receptors on their sperm

Male mosquitoes, which don't bite humans, have fewer olfactory receptors than females on their antennae—they don't need them to locate blood meals. But they do have this same type of receptor located in the tail of their sperm, thought to help bring egg and sperm together.

The hippocampus, located deep inside the temporal lobe, appears to play a central role in dreaming and memory, according to recent research on dreaming and damage to that area of the brain.

Some animals may anchor their brain cells to specific landmarks to determine direction

In a study of bats exploring a new area, specific sets of "head direction cells" were seen becoming active based on bats' orientation when moving, and this activity became more coordinated over time. Researchers suspect, like humans, bats and other animals establish this sense of direction based on movement relative to known points of interest.

Why do some people always get lost?

Using GPS, anthropological data, and VR, scientists have learned that one's sense of direction is largely influenced by upbringing. A person's wayfinding ability can be measured by how accurately they point toward an out-of-sight location, a challenge further complicated by imagining they're somewhere else and pointing toward a third location. Anxiety, safety concerns, and dislike of wandering can negatively impact one's sense of direction, which can improve with practice.

Some animals may speak because of duplicated connections in the brain

Neuroscience suggests that connections responsible for motion made during embryonic brain development—such as those connecting hearing and movement pathways that allow reactive motion when started—are duplicated and connected to the larynx in some animals. This allows some mammals and song-learning birds to speak, provided they have the necessary physiological structures.

Why human brains were bigger 3,000 years ago

Our modern civilisation may be the most advanced to ever exist on Earth, but around 100 generations ago, our ancestors had brains that were larger than our own.

What a tiny marine worm can tell us about our brains

Meet the amphioxus, a small eel-like animal that has a lot to teach us about brain evolution. The genetic roots of our brains can be seen in these unusual creatures. This three-minute educational video focuses on the evolutionary history of the human brain through these odd little critters with a 500-million-year-old history.

The science of optical illusions

The human brain has developed cognitive shortcuts to help us navigate in a world where our visual senses are constantly bombarded of information. But these shortcuts can also be exploited, tricking the brain into telling us something is happening when it really isn't. This short video unpacks the neuroscience behind some of the most common (but perplexing) optical illusions.

The study of dreams, formally called oneirology, has evolved over the centuries, from anecdotal interpretations to advanced brain imaging.

When processing light, the brain can perceive colors with no natural wavelength

While some animals are sensitive to many forms of light, humans possess receptors that are sensitive to red, green, and blue wavelengths. These receptors send signals to the brain, which are processed and mixed to produce the array of colors we observe, including magenta, pink, and "supercolors" that lack a corresponding natural wavelength in the visible spectrum.

Typhoid smells like freshly baked brown bread

Certain ailments are associated with documented scents, including diabetes, Parkinson's disease, and typhoid. The skin of people with yellow fever, for example, can smell like a "butcher shop."

How do brain scans work?

There’s only one thing in our solar system sophisticated enough to study itself: the human brain. But this self-investigation is challenging because a living brain is shielded by skull, swaddled in tissue, and made up of billions of tiny cells. How do we study living brains without harming their owners? Two experts explain how the various techniques like EEGs, fMRIs, and PETs work in this TedEd talk.

Always forget a face? The science of face-blindness

Faces and names don't always go together in some people's minds. While everyone forgets other peoples's names occasion, people diagnosed with prosopagnosia can't recognize faces, much less names. Even friends can family members can appear to be strangers. This article covers the diagnosis and issues attendant to prosopagnosia and its sufferers.

Why humans survived and smarter species did not

This interview with Joseph Henrich, a renowned professor of human evolutionary biology, unpacks human history. Henrich shares interesting information about why humans succeeded as a species (the answer isn't IQ), how cultural evolution works, why the human brain is shrinking, and how the Catholic Church played a role in the Industrial Revolution. Listen and watch for a deep dive into human evolution.