How dogs can know if a person is good or bad

You’ve probably heard that dogs can smell fear — but what if they could also sniff out lies? Turns out, your pup may be more perceptive than you ever imagined.

A series of new studies reveals that dogs don’t just love unconditionally — they actually pay close attention to human behavior, and they can figure out pretty quickly who’s trustworthy… and who isn’t.

Three-part experiment with 34 dogs

Humans mostly rely on sight to understand the world, but it’s easy to forget that dogs experience life primarily through their sense of smell. This powerful ability gives them a completely different — and often deeper — perspective on their surroundings.

In one clever study out of Kyoto University in Japan, researchers led by Akiko Takaoka set out to test just how smart dogs really are when it comes to human trust. And what they found was jaw-dropping — even for seasoned dog lovers.

They ran a three-part experiment with 34 dogs. First, a person pointed toward a container with hidden food. The dogs happily trotted over and found the treat. In round two, that same person pointed to a container that was empty. The dogs went, but this time came up empty-pawed. By round three, when the human tried to regain their trust by pointing to another food-filled container, the dogs refused to go. Every. Single. One.

They had figured it out: this person had lied to them once before — and they weren’t about to be fooled again.

“Dogs have more sophisticated social intelligence than we thought,” said Takaoka.

“This social intelligence evolved selectively in their long life history with humans.”

In other words: lie to your dog once, and good luck earning back their trust.

But that’s not where the science ends. Over in the UK, another team of researchers from the University of Bristol, Cardiff University, and Medical Detection Dogs wanted to explore how dogs respond emotionally to human stress — and what they found makes it even more clear that our canine companions are incredibly in tune with us.

They ran a study, published in the journal Scientific Reports, that involved collecting the scent of stressed-out people — volunteers who had to give a surprise speech and complete a tough math challenge while being watched by stone-faced researchers. After the anxiety-inducing experience, samples of their sweat and breath were collected and stored in jars.

Stress smell might affect how dogs respond

Then, dogs were brought into a testing room where they had to choose between different food bowls, some in known locations and one placed in an “ambiguous” middle spot. When dogs were exposed to the scent of a stressed person before the test, they were less likely to optimistically approach the mystery bowl — they assumed there wouldn’t be food. The same test, done with relaxed human scents, didn’t produce that cautious reaction.

Dr. Zoe Parr-Cortes, the study’s lead author, explained, “The stress smell might affect how dogs respond to ambiguous situations. They might be less likely to try something risky if they think they’re going to be disappointed.”

So not only can dogs detect stress in humans, but that stress actually shifts their mindset — making them more cautious, less hopeful, and emotionally reactive.

This has real implications for how we interact with our dogs day to day. If you’re anxious or upset while trying to train your dog, they might be less engaged, more hesitant, and pick up on your frustration. They don’t just react to our tone — they smell our mood, and it changes their entire outlook.

If crowded places make you feel anxious, chances are your dog might be picking up on that too — and feeling the same way.

“If you’re stressed, you’re probably more likely to be tense and not as patient,” says Dr. Zoe Parr-Cortes, a veterinarian and Ph.D. student at Bristol Veterinary School who was the lead author on the British study. “[And it] might literally make them have different behaviors. I think that’s really, really important to know.”

What does this all mean?

And here’s another wild fact from the Kyoto study: dogs weren’t just gauging trust based on their own experience. In some cases, they even refused treats from people who were rude to their owners. That’s right — dogs take notes on how you treat their favorite humans. If someone yells at you or ignores you when you’re in need, your dog might decide that person isn’t worth wagging their tail for.

So what does this all mean?

It means your dog is watching. They’re listening. They’re smelling. They’re remembering. And they’re making decisions based on all of it. Dogs don’t just blindly trust — they’re discerning, emotional, and wildly loyal.

If your dog seems uneasy around someone, pay attention. They may have picked up on something you didn’t. And if you’re feeling down or overwhelmed, your pup might be feeling it too.

At the end of the day, dogs are more than just man’s best friend — they’re little emotional barometers with fur and four legs. They want to be happy, safe, and secure. And they want the same for you.

So the next time you’re with your dog, remember: be honest, stay calm, and trust their instincts. They might just be the best judge of character you’ve got.