Fear has a specific 'smell'—at least to machines

Fear (and stress) can be contagious via pheromones secreted by the body

While seeing someone else in a panicked state may induce a stress response, researchers have found stress can be literally contagious—chemicals contained in sweat and other secretions can trigger stress hormone release in others. Theories suggest this feature is an evolutionary adaptation to protect groups from danger.

The science of fear

The Hidden Brain podcast team explores the science of fear by traveling to a haunted house curated by a scientist to investigate what scares us, and why some people enjoy this sensation more than others.

A 'fishy' scent does lead to mistrust

In experiments where people were exposed to a literal fishy smell they were less willing to cooperate with others in economic games requiring trust, but that wasn't the case when they were exposed to another bad odor—the smell of flatulence.

Fearology, or the study of fear, explores the difference between stress and fear

Our brains involuntarily respond to our environment and signal alarm when that isn’t always needed, triggering responses that include goose bumps. But understanding fear and how to talk our brains into calming down can improve daily life.

See these 16 pieces of art evoking phobias of snakes, flying, spiders, and more. 

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights

Dr. Martin Antony, a Canadian expert on phobias and anxiety, says that fears of creepy, crawly animals like snakes, spiders, and mice are particularly common.

Some theorize that horror's artifice turns fear into enjoyment

The “excitation transfer theory” suggests that the unpleasant feelings a jump scare might elicit (like shortness of breath) are quickly relieved when the audience member remembers what they’re witnessing is fake.

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.

'Sweat dating' is a dating approach where partners specifically select by body odor

With dedicated events in major cities around the world, "sweat dating" offers people the chance to judge if a potential partner's smell is a match. Participants show up for an event, do calisthenics, wipe themselves with a cotton pad, and then place the smelly pad in a numbered jar for potential partners to sniff.

Sweat doesn't smell, but bacteria multiply in moist environments—and cause an odor

Body odor is associated with sweat, but odor actually arises from the bacteria that multiply in moist environments on your skin. Hormones, medications, food, and body hair can all affect body odor.

See 16 art pieces that were inspired by or evoke elements of top phobias

CBC News informally polled readers about their fears and then found works of art either inspired by or nodding to those topics.

Charles Darwin studied goose bumps by scaring zoo animals in London with a stuffed snake

Read the famous naturalist’s work from the late 1800s, detailing how he sought to draw comparisons between how animals and humans respond to fear. As part of that work, he exposed monkeys and a peccary to a stuffed snake and noted the animals’ hair-raising fear response.

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.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

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.

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.

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

Dogs smell a lot of stuff we can't, including bed bugs and chemicals in electronic devices

In addition to identifying medical smells and tiny insects like bed bugs, dogs can also detect electronic storage devices. These tools often contain triphenylphosphine oxide, a chemical used to prevent overheating.

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

Odor blockers use nonpolar oils to trap smelly polar molecules

In the case of feces, gut bacteria produce compounds such as skatole and hydrogen sulfide, which the brain registers as unpleasant. Because oils do not dissolve in water, they can be used to create a layer on the surface that prevents smelly compounds underwater from escaping into the air.

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."

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.

Twin studies helped scientists understand why mosquitoes like some of us more than others

A combination of carbon dioxide output, skin chemistry, genetic factors, hormones, and clothing choice can make us particularly vulnerable to mosquito bites. Watch how mosquitoes responded to one man in the video versus his wife, a research approach typically conducted with identical and fraternal twins to test mosquito attractiveness.

Astronauts agree: The moon smells like gunpowder

Twelve astronauts have walked on the moon to date, and they all agree that our lunar neighbor smells like gunpowder. Scientists argue this scent comes from unstable minerals that cling to their suits and the rocks they return to the ship. Notwithstanding, space itself has a different smell, often compared to steak or metal, which experts believe, rather poetically, is the smell of dead stars.

Explore some of the trademarked scents in the US

Scents, when they are truly unique and identifiable to a particular brand, can be trademarked. Any trademark on a scent must pass two tests: distinctiveness and non-functionality. In order to be trademarked, the scent of a product can't be the primary purpose of that product (like a candle or a perfume), and the scent has to be distinct. Some of the trademarked scents include Play-Doh and the pain-relief patch Salonpas.

Misophonia is a neurological disorder where sounds trigger strong emotions

The phenomenon is characterized by decreased tolerance to specific sounds, such as heavy breathing, pen clicking, and water dripping, which trigger a fight-or-flight response. The resulting emotions, which can range from irritation and disgust to anxiety and fear, can be overwhelming and uncontrollable.

Cold-blooded reptiles seek heat, and that behavior may help combat fungal infections

This Radiolab podcast episode takes on the idea that though our human bodies are too warm for the majority of fungal species to effectively replicate inside our bodies, that's not the case for reptiles. Yet when those species warm their bodies by basking in the sun on rocks, they can soak up heat and may also help keep fungal infections in check.

Over time, people develop a resistance to spicy foods

TRPV1 is a receptor in the body that detects potentially harmful things and responds in a variety of ways, including sweating, tearing up or a runny nose. Over time, more exposure to spicy foods can build up a resistance that minimizes these reactions.

Depending on environment, aliens' bodies would have wide-ranging possibilities

Humans tend to imagine aliens as humanlike, but that's probably unlikely. From small space spiders to metallic carnivores, life on other planets—and how we could interact with it—is difficult to imagine.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Ebola is a filovirus, meaning it resembles a thread under a microscope, though it sometimes twists and can resemble a bowl of spaghetti.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

Browse a detailed visual analysis of over 200,000 similes—comparisons that often use 'like' or 'as'—from popular fiction to see how frequently writers the same idiomatic expressions.

When a Paris department store hesitated to sell Estée Lauder's perfume, she 'accidentally' broke a bottle, causing the smell to spread throughout the store and shoppers to start asking to buy the scent.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

Chaos theory—informally known as the butterfly effect—is the reason why weather forecasts are presented with probabilities rather than certainties.

Existentialist writer Jean-Paul Sartre coined the famous phrase 'Hell is—other people' in his play 'No Exit'

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

The history of many kitchen appliances involves unexpected discoveries and applications, including wartime radar turned hamster defroster and replacing an 'ice king' with heat-stealing boxes.

Some coin denominations have ridges etched on their sides, partly to prevent counterfeiting, in a practice called 'reeding.'

As of 2025, the most cited papers in science include a review of graphene, methods to improve image recognition, streamlining electron density calculations, and optimizing protein studies.

'Saturday Night Fever,' the 1977 film that introduced disco to the mainstream, was based on a fabricated magazine story.

Dorothy's famous entrance into Oz in 'The Wizard of Oz' relied on analog tricks, including a body double and sepia-toned paint, as much as it did on technology

Hedge funds, the private investment firms that trade a wide swath of financial assets, make money by imposing steep fees on investors and from the fund's investment performance.