A new study by researchers at the Tokyo University of Agriculture, Japan, identified patterns of behavior shown by cats towards humans they know, such as their owners, and strangers.

Previous research suggested cats rely on their sensitive noses to identify other cats as friend or foe. But whether that same function applies to detecting humans was not fully understood. So, the researchers in Japan took 30 domestic cats and tested their responses to a range of special scents.

The cats' owners provided samples of their scents by swabbing their underarms, behind their ears and between their toes. These swabs were then presented to the cats in a tube. And the researchers monitored the behavior shown by each cat and the time they spent sniffing the scent samples.

They repeated the process with swabs from humans the cats did not know, and also with a blank swab, or placebo, as a measure to control or verify the test.

Their results appear to show that the cats spent twice as long smelling samples from strangers than samples from their owners, and that they favored their right nostrils over their left nostrils when sniffing the swabs from strangers.

The research team thinks the choice of nostril may correspond to the way in which many animals process new information.

"Dogs, but also fish, birds, and other vertebrates process novel information using the right brain hemisphere," they wrote in a study paper published May 28, 2025, in the journal PLOS One. "The left brain is responsible [...] when a routine response emerges."

The researchers said that while their findings suggested a cat's sense of smell was a tool for their recognizing humans, they could not conclude that smell was the most important mechanism for cats to do that.

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A cat's personality influences how they interact with humans

Personality traits may also play a role in how cats interact with odors — human or otherwise.

The researchers asked the cat owners to complete a survey about their cats' personalities. They then tried to match those personality traits with the behaviors they observed during the smelling test, in a hope that this would enable them to identify behavioral differences among cats in responding to smells.

They observed that among male cats, the more "neurotic" ones repeatedly returned to the smell tubes, while those described as being more "agreeable" rarely returned to a scent. No behavioral differences were identified among female cats.

The personality traits were quantified using a test known as "the Feline Five." That test was developed by another research team for a study of about 3,000 cats in Australia and New Zealand.

In that study, published in 2017, highly neurotic cats were described as "insecure, anxious, fearful [of people], suspicious and shy." More agreeable cats were described as "affectionate, friendly to people and gentle."

The test was originally pitched as a tool to support animal welfare in the home, by helping owners create safe environments for their cats.

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Another attempt to understand mysterious 'moggies'

While dogs are often called "man's best friend," cats have a reputation for being mercurial, wayward, untamed domestic cohabiters.

For example, one study from the University of Leeds found that cats don't bond with humans in the same way as dogs do: "Adult cats are typically quite autonomous, even in their social relationships, and not necessarily dependent on others to provide a sense of security and safety," said the authors of that study when it was published in 2015.

So, although this latest study from Japan may suggest cats are able to recognize their human companions, they may still think very little of them.

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