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August 11, 2025<\/p>\n
4 min read<\/p>\n
Pessimistic Dogs Are Better at Smelling Cancer\u2014And Other Keys to Disease-Sniffing Success<\/p>\n
New research is revealing how disease-smelling dogs can excel<\/p>\n
By Rohini Subrahmanyam edited by Sarah Lewin Frasier<\/span><\/p>\n Individual dogs\u2019 personalities, and how we interpret their behaviors, may be key to disease sniffing at scale.<\/p>\n Johner Images\/Getty Images<\/p>\n Billy, a floppy-eared little beagle, darts around a platform sniffing a series of holes. Each hole contains a used surgical-type mask bearing a different human\u2019s distinct mix of scents. But her sharp nose is hunting for just one such combination: the one that signals cancer.<\/p>\n Cancer can change a person\u2019s \u201cvolatilome,\u201d the unique set of volatile organic compounds found in breath, sweat, blood and urine. Billy and her cohort have learned to sniff out these subtle scent cues in masks worn by people with cancer diagnoses. Researchers are also studying how dogs can detect diseases such as COVID and malaria, as well as psychological conditions, including post-traumatic stress disorder.<\/p>\n Scientists discovered dogs\u2019 powerful disease-smelling skills in 1989, when a dog detected cancer in its handler. But clinicians still do not routinely use dogs for diagnosis. Besides the obvious logistical challenges, dogs vary greatly in their olfactory accuracy. Researchers are increasingly finding that disease-sniffing prowess may come down to individual dogs\u2019 personality\u2014and how well their handlers know them. New research efforts are focused on figuring out which dogs would be best for the job and on interpreting dogs\u2019 behaviors during a smell test.<\/p>\n If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n Sharyn Bistre Dabbah, a veterinary scientist now at the University of Bristol in England, set out with colleagues at the U.K. charity Medical Detection Dogs to learn how the animals\u2019 personalities\u2014especially their level of optimism or pessimism\u2014affect disease-detection skills. Their results appeared recently in PLoS One.<\/p>\n The researchers first showed the dogs what lay behind two screens at one end of a room: a \u201cpositive\u201d location with a tasty treat and a \u201cnegative\u201d one with an empty bowl. On subsequent visits to the room, the dogs typically bounded happily toward the former but trotted very slowly when they went to check out the latter\u2014or simply didn\u2019t go there at all.<\/p>\n The scientists then placed bowls behind two new screens between the positive and negative spots, and they classified the dogs as \u201coptimistic\u201d or \u201cpessimistic\u201d based on how quickly they investigated these new locations.<\/p>\n Next, the team evaluated how accurately each dog could pick out a disease scent it was trained to detect among other smells. On average, the pessimistic dogs turned out to be more discerning. Pessimistic dogs are more cautious, and \u201ca more cautious dog might be better at not making mistakes,\u201d Dabbah says.<\/p>\n Other personality traits also play a role, says Clara Wilson, who researches disease- and stress-sniffing dogs at the University of Pennsylvania. Dogs that enjoy the thrill of a hunt\u2014and thrive while searching for missing people or hidden bombs\u2014might find sniffing through disease samples again and again rather repetitive. \u201cWe want a dog that doesn\u2019t get frustrated. They [should] find it rewarding, even though it may be less exciting,\u201d Wilson explains.<\/p>\n Handlers\u2019 interpretations of dog behavior can also skew detection outcomes, says Akash Kulgod, co-founder of Dognosis, the Bengaluru-based start-up that trained Billy. Instead of teaching dogs to perform a specific behavior such as sitting or barking when they pick up an assigned scent\u2014a process that takes extra time and can lead to dogs \u201clying\u201d for treats\u2014Kulgod and his team directly analyze each dog\u2019s natural body language. Based on how confidently the dogs move, as analyzed with computer vision\u2013based machine-learning tools, the team can spot successful detections. \u201cOne of our dogs sniffs and then very confidently somersaults to go to the feeder,\u201d Kulgod says. \u201cThey each have their own unique quirks\u2014but all of it can be quantified because it\u2019s all related to this reward expectation that you have from the past sessions.\u201d<\/p>\n In a pilot study with 200 test samples involving 10 cancer types, presented at this year\u2019s American Society of Clinical Oncology conference, Dognosis dogs detected 96 percent of cancers. Next, the Dognosis team will scale up its study with 1,500 test samples.<\/p>\n Doctors currently diagnose many kinds of cancers by using a combination of blood tests and biopsies. Researchers are always on the lookout for less invasive methods\u2014including options directly involving our canine companions, as well as electronic noses inspired by them. Dogs can currently outperform electronic sniffers. But this primacy may not last, according to Andreas Mershin, chief science officer at the Boston-based start-up RealNose.ai. He and his colleagues are developing electronic noses to sniff urine samples for prostate cancer and other diseases. If machine olfaction eventually surpasses dogs\u2019 abilities, it could help tackle the scalability problem\u2014and give the animals a break.<\/p>\n Mershin\u2019s team put mammalian smell receptors on an electronic chip and used machine-learning algorithms to interpret the output. The technique focuses on broader patterns among detected molecules rather than categorizing them individually.<\/p>\n Dogs don\u2019t tick off a list of molecules in their heads, either; they just \u201cknow\u201d what cancer smells like. This helps them to sense it accurately no matter which organ it is from or what the patient ate before giving their breath sample. \u201cThe dogs can generalize. They don\u2019t care about the font in which you write the scent; they just interpret it correctly,\u201d Mershin says.<\/p>\n In a study published in PLoS One, Mershin and his team used machine-learning models to spot and analyze patterns of different odorants in urine samples from confirmed prostate cancer patients. Their findings, which built on work with diagnosis data from Medical Detection Dogs, suggest that focusing on this type of \u201cscent character\u201d might work as a scalable alternative to dogs, even if it\u2019s currently much slower.<\/p>\n Meanwhile, back on the test platform, floppy-eared Billy quickly detects the subtle scent of cancer in one of the masks she has been sniffing\u2014and confidently bounds back to get her reward. Such tests show strong potential, says postdoctoral researcher Amritha Mallikarjun of the University of Pennsylvania: \u201cThe dogs, because of their amazing sense of smell and detection capabilities, are demonstrating to us what technology could look like 10 to 15 years from now.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":" August 11, 2025 4 min read Pessimistic Dogs Are Better at Smelling Cancer\u2014And Other Keys to Disease-Sniffing Success New research is revealing how disease-smelling dogs can excel By Rohini Subrahmanyam edited by Sarah Lewin Frasier Individual dogs\u2019 personalities, and how we interpret their behaviors, may be key to disease sniffing at scale. 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