News / Science & Technology

Study Finds Humans Can Smell at Least 1 Trillion Odors

FILE - A visitor smells a Sir Paul Smith climbing rose at the Chelsea Flower Show in London, May 21, 2013.
FILE - A visitor smells a Sir Paul Smith climbing rose at the Chelsea Flower Show in London, May 21, 2013.
Jessica Berman
One trillion.

That’s the number of scents researchers have determined humans can detect through their sense of smell. Scientists say the figure is probably a conservative estimate.

Popular and scientific literature since the 1920's has put the number of odors detectable by humans at around 10,000.

But, in a new study published in the journal Science, researchers at Howard Hughes Medical Institute and Rockefeller Institute in New York City calculated the number of odors detectable by humans as much, much higher.

Andreas Keller was co-author of the study which challenged volunteers to sniff scents in three tiny bottles. The researchers mixed 128 odor molecules in combinations of 10, 20 and 30 molecules.

The resulting subtle odors were both pleasant, including grass and citrus, and distasteful, such as sweaty socks. Two of the bottles were an identical blend. The third bottle was altered slightly.  

Extrapolating from how often the volunteers could identify the different scent, the scientists calculated humans could discriminate at least one trillion odors. Keller believes the human nose is sensitive enough to detect more than that.

“Obviously in reality there are many more than 128 molecules that you can mix up and you can mix them in mixtures of more than 30,” he said.

How does that compare to dogs, which are held up as the "gold standard" of scent identification? Keller says our sense of smell is probably at least as good as a canine’s. Our noses are just higher than a dog's.

“In my opinion, the main difference between you and your dog when you go for a walk is that the dog’s nose during walking is always very close to the ground, which is where the interesting smells are," Keller said.

"So, the reason the dog picks up all those interesting smells and you don’t isn’t that the dog’s nose is better than you. It’s that the dog’s nose is closer to where the action is,” Keller said.

Researchers hope to use their findings to shed light on how the brain processes sensory information.

You May Like

Multimedia Brussels Schools, Metro Reopen Under Heavy Guard

City remains under the highest threat alert level due to what authorities have described as a 'serious and imminent' threat of attack

Video Debt-ridden Refugees Await Onslaught of Lebanese Winter

Aid agencies are attempting to reduce potentially devastating consequences of freezing conditions and snowstorms that killed eight last year, including three Syrian refugees

Americans Think About Strange Stuff at Thanksgiving

Millions of Americans are celebrating Thanksgiving, but they’re not necessarily thinking about turkey and stuffing

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
After Paris Attacks, France Steps Up Fight Against ISi
November 24, 2015 3:04 AM
The November 13 Paris attacks have drawn increased attention to Syria, where many of the suspected perpetrators are said to have received training. French President Francois Hollande is working to build a broad international coalition to defeat Islamic State in Syria and in Iraq. Zlatica Hoke reports.

Video After Paris Attacks, France Steps Up Fight Against IS

The November 13 Paris attacks have drawn increased attention to Syria, where many of the suspected perpetrators are said to have received training. French President Francois Hollande is working to build a broad international coalition to defeat Islamic State in Syria and in Iraq. Zlatica Hoke reports.

Video US, Cambodian Navies Pair Up in Gulf of Thailand

The U.S. Navy has deployed one of its newest and most advanced ships to Cambodia to conduct joint training drills in the Gulf of Thailand. Riding hull-to-hull with Cambodian ships, the seamen of the USS Fort Worth are executing joint-training drills that will help build relations in Southeast Asia. David Boyle reports for VOA from Preah Sihanouk province.

Video Americans Sharpen Focus on Terrorism

Washington will be quieter than usual this week due to the Thanksgiving holiday, even as Americans across the nation register heightened concerns over possible terrorist threats. VOA’s Michael Bowman reports new polling data from ABC News and the Washington Post newspaper show an electorate increasingly focused on security issues after the deadly Islamic State attacks in Paris.

Video World Leaders Head to Paris for Climate Deal

Heads of state from nearly 80 countries are heading to Paris (November 30-December 11) to craft a global climate change agreement. The new accord will replace the Kyoto Protocol on Climate Change that expired in 2012.

Video Uncertain Future for Syrian Refugee Resettlement in Illinois

For the trickle of Syrian refugees finding new homes in the Midwest city of Chicago, the call to end resettlement in many U.S. states is adding another dimension to their long journey fleeing war. Organizations working to help them integrate say the backlash since the Paris attacks is both harming and helping their efforts to provide refugees sanctuary. VOA's Kane Farabaugh reports.

Video Creating Physical Virtual Reality With Tiny Drones

As many computer gamers know, virtual reality is a three-dimensional picture, projected inside special googles. It can fool your brain into thinking the computer world is the real world. But If you try to touch it, it’s not there. Now Canadian researchers say it may be possible to create a physical virtual reality using tiny drones. VOA’s George Putic reports.

Video New American Indian Village Takes Visitors Back in Time

There is precious little opportunity to experience what life was like in the United States before its colonization by European settlers. Now, an American Indian village built in a park outside Washington is taking visitors back in time to experience the way of life of America's indigenous people. Carol Pearson narrates this report from VOA's June Soh.

Video Even With Hometown Liberated, Yazidi Refugees Fear Return

While the northern Iraqi town of Sinjar has been liberated from Islamic State forces, it's not clear whether Yazidi residents who fled the militants will now return home. VOA’s Mahmut Bozarslan talked with Yazidis, a religious and ethnic minority, at a Turkish refugee camp in Diyarbakır. Robert Raffaele narrates his report.

Video Nairobi Tailors Make Pope Francis’ Vestments

To ensure the pope is properly attired during his visit, the Kenya Conference of Catholic Bishops asked the Dolly Craft Sewing Project in the Nairobi slum of Kangemi to make the pope's vestments, the garments he will wear during the various ceremonies. Jill Craig reports.

Video Cross-Border Terrorism Puts Europe’s Passport-Free Travel in Doubt

The fallout from the Islamic State terror attacks in Paris has put the future of Europe’s passport-free travel area, known as the "Schengen Zone," in doubt. Several of the perpetrators were known to intelligence agencies, but were not intercepted. Henry Ridgwell reports from London European ministers are to hold an emergency meeting Friday in Brussels to look at ways of improving security.

Video El Niño Brings Unexpected Fish From Mexico to California

Fish in an unexpected spectrum of sizes, shapes and colors are moving north, through El Niño's warm currents from Mexican waters to the Pacific Ocean off California’s coast. El Nino is the periodic warming of the eastern and central Pacific Ocean. As Faiza Elmasry tells us, this phenomenon thrills scientists and gives anglers the chance of a once-in-a-lifetime big catch. Faith Lapidus narrates.

Video Terrorism in Many Forms Continues to Plague Africa

While the world's attention is on Paris in the wake of Friday night's deadly attacks, terrorism from various sides remains a looming threat in many African countries. Nigerian cities have been targeted this week by attacks many believe were staged by the violent Islamist group Boko Haram. In addition, residents in many regions are forced to flee their homes as they are terrorized by armed militias. Zlatica Hoke reports.

Video Study: Underage Marriage Rate Higher for Females in Pakistan

While attitudes about the societal role of females in Pakistan are evolving, research by child advocacy group Plan International suggests that underage marriage of girls remains a particularly big issue in the country. VOA’s Ayesha Tanzeem reports how such marriages leads to further social problems.

VOA Blogs