Can Dogs Tell If Someone Is a Bad Person?

I used to trust animals’ judgement so much that when my dog didn’t like someone, I assumed there must be a good reason. My ex’s dog was never that keen on me, and I always thought it’s was because she knew the relationship was going south before we did.

When I raised the subject with my friends, one told me that her dog always hated a guy who regularly came into her workplace, even though he seemed shy and nice. “My dog would always get so riled up when he came in, barking at him, sniffing him and backing away,” she tells me. “We even drove past him in the street once and she still hated him! I always felt so guilty about her behaviour until I later found out that he’d stolen from a lot of people, and left restaurants without paying.” Another pal’s dog hated her friend’s boyfriend – it later transpired that this guy had been lying and stealing from her the whole time. 

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It’s stories like this that previously strengthened my belief that our dogs just know. Years ago my dog was off lead when he nipped a man from behind for seemingly no reason. The man did give off bad vibes, so I assumed that Sherlock had sensed these too. (I know, I know, making excuses for my wayward son and my poor training…).

However, my trust in the sixth sense of canines started to wane when I found myself on the receiving end of a disdainful dog. While my brother’s 14-year-old Cockapoo absolutely adores me, his new puppy hates me, growling and barking whenever I enter the room. What gives? Am I a secret douchebag?

I wanted to find out the truth once and for all, so I turned to dog behaviourists to find out if we should trust our dog’s judgement or if we’re barking up the wrong tree…

Are dogs psychic?

Research published in June looked at how dogs behaved after observing humans being naughty or nice to other dogs. In this context, being ‘naughty’ was withholding food from them, and being ‘nice’ was sharing their food. Curiously, the dogs didn’t behave any differently towards the human participants, regardless of whether they shared food or not. However, an older study from the same university showed that dogs refused to take treats from humans who had behaved negatively towards their pet parents. (A+ for loyalty, guys.) But this is about overt behaviours they’ve witnessed – what about plain old sixth sense? Are they vibe sensor extraordinaires? 

While there’s no evidence for dogs being psychic (booooo), multiple studies show that dogs can read human emotions, so can their heightened senses allow them to detect nuances in an ill-intentioned person’s demeanour that we might miss? 

Dogs are great at reading people

After falling down an internet hole of reading pet parents’ anecdotes about their dogs being mind readers, I realised I needed to speak to an actual expert, so jumped on a call with Julia Hawkins, a canine behaviour consultant and dog trainer at All to Play For and Barking up the Right Tree. 

“There’s one thing that we know without any shadow of a doubt is that our dogs are brilliant at reading our emotional state,” Hawkins tells me. “They’re really good at reading facial expressions, and voice tone.”

While humans can also be pretty good at decoding faces and voices, dogs have the edge on us with their super duper sense of smell, which is estimated to be 1,000 to 10,000 times more sensitive than ours. Why does this matter when it comes to sniffing out wrong ‘uns?

“When we’re stressed or angry our chemical composition within our brains will change,” explains Hawkins. “These chemicals go into our blood stream and sweat, and people sweat more when stressed. Dogs will pick up on that in a heartbeat.”

In fact, research confirms that dogs can smell whether we’re stressed or relaxed. So, in the case of the seemingly shy guy who was going around stealing, my friend’s dog may well have picked up on his pre-theft stress sweat. 

“As well as scenting, dogs communicate through their bodies, so they tend to pick up on those same cues from us,” adds Hawkins. “Something thats threatening behaviour from a dog, like staring, for example, could also seem threatening from a human, regardless of the intent.”

She explains that a relaxed dog will have flowy movement, which then turns into more jerky movements – or even a freeze – when their arousal level goes up when they’re stressed or excited. So if a human is acting a little stiff and awkward, a dog might pick up on that and perceive it as a threat. 

One 2019 study showed how specially trained dogs were able to accurately predict violent outbursts in unfamiliar psychiatric patients, identifying physiological changes using sight, sound, and smell. The more the dogs did this, the better they got, showing that dogs appear to learn patterns of behaviour. 

However, it’s important to note that anxiety disorders are the most common mental health disorder globally, with 22.6 percent of adults in the UK reporting high levels of anxiety. We already know that we smell different when stressed, but while dogs can detect this, they may not be able to pick up on the nuances of why someone is stressed. Basically, our canine companions don’t understand that having social anxiety doesn’t make someone a bad person…

Clinical animal behaviourist, Emily Birch also points out that not everyone loves dogs (or unfamiliar dogs), which will affect how they behave around our pets. 

“Dogs get really unnerved by people acting unsure,” she tells me. “I definitely in practice see dogs who can’t cope with unconfident people – so those who might shy away, or go really still and just act a bit stiff and unnatural. This of course doesn’t mean it’s okay for your dog to scare them, but I do see that dogs are often really unsure of nervous people and fine with confident people.”

In the case of the guy with ‘bad vibes’ who my dog nipped – there’s a chance he was feeling nervous around my off-lead dog, which then caused my dog to react negatively. (And that’s on me – I should absolutely have been more aware of the situation).

Other reasons your dog might dislike someone

Aside from smelling our stress and assessing our tone of voice and body language, dogs may also pick up on the following:

Your reaction

As well as reading the other person’s behaviour, our dogs will also be looking for any subtle signals we’re giving off around the offending human. Say, for example, you’re walking your dog alone at night and you suddenly see someone coming towards you that you hadn’t seen. You might subconsciously be on alert, which Birch says your dog will absolutely pick up on. 

Learned triggers

If a dog has had a bad experience with someone who wears certain clothes/has a beard/smells a particular way, Birch says they may generalise and react negatively when they encounter these triggers on other humans. Hawkins has a great example of this, with her dog Patty, who was rescued from an abusive shelter in Romania. 

“We were in a quiet cafe once where a man walked in and Patty went absolutely ballistic,” she tells me. “I realised it was because he stank of cigarette smoke, and the men who worked in the shelter would smoke. So it was a learned response – she really struggles with people who smell of cigarettes.”

Fear of change

Ever noticed that your dog was fine with someone the first time they met them and then freaked out every other time? This could be due to fear of change.

“Humans change their looks frequently with changes of hair, umbrellas, big coats, sunglasses, hats, etc,” says Birch. “Ths can make a dog worry if they haven’t learned that changing and novelty is safe and OK.”

Can certain breeds read people better than others?

Like us humans, dogs have their quirks, which could explain why your dog might love someone while your friend’s dog hates them. But does breed come into play? Maybe.

“There are some breeds that have a tendency to be more sensitive to humans,” Hawkins says. “It tends to be working breeds and dogs that we’ve bred to work in conjunction with people, like Border Collies or Spaniels. That’s also why we train certain breeds such as Spaniels or Labradors to be scent detection dogs.”

However, Hawkins stresses that it’s important not to generalise too much.

“It’s more important that we look at the dog in front of us,” she advises. “Dogs are individuals and we need to see and work out why they’re behaving the way they are. That’s far more important than breed.”

Why does my dog love someone terrible?

You’ve probably realised by now that a dog’s judgement may not be infallible. Or maybe you already know this because your dog is obsessed with an absolutely hideous human.

“Dogs have a different level of what gives them the ‘ick’ to humans,” explains Birch. “They don’t understand narcissistic behaviour, for example.” 

Ever had to stand back and watch aghast as your dog goes all soppy over an ex-partner who wronged you? The worst kind of betrayal, right? Well, don’t take it too personally, as Birch says it’s normal for them to get super excited to encounter a familiar person they haven’t seen in a while.

Plus, dogs can also be simple creatures and food-oriented types may well be won over easily with treats. The schmucks.

So, while we shouldn’t blindly trust our dogs’ character assessments, we should be paying attention to when our dogs are uncomfortable around specific people, trying to understand why, and giving them the space they need (especially if they’re on a lead and can’t physically move away themselves). As Hawkins says, it’s our job as caregivers to make our dogs feel safe.

Resources

Jim, Hoi-Lam, et al. “Do Dogs Form Reputations of Humans? No Effect of Age After Indirect and Direct Experience in a Food-giving Situation.” Animal Cognition, vol. 28, no. 1, June 2025.

“Dogs Avoid People Who Behave Negatively to Their Owners.” KYOTO UNIVERSITY, 24 June 2015.

Albuquerque, Natalia, et al. “Mouth-licking by Dogs as a Response to Emotional Stimuli.” Behavioural Processes, vol. 146, Nov. 2017, pp. 42–45.

Lehoczki, Fanni, et al. “Family Pigs’ and Dogs’ Reactions to Human Emotional Vocalizations:a Citizen Science Study.” Animal Behaviour, vol. 214, July 2024, pp. 207–18.

“How Dogs Use Smell to Perceive the World  | VCA Animal Hospitals.” VCA. Accessed 16 August, 2025.

Harvard Health. “Understanding the Stress Response.” Harvard Health, 3 Apr. 2024. 

Parr-Cortes, Z., et al. “The Odour of an Unfamiliar Stressed or Relaxed Person Affects Dogs’ Responses to a Cognitive Bias Test.” Scientific Reports, vol. 14, no. 1, July 2024.

Bakeman, Uriel, et al. “Detection of Impending Aggressive Outbursts in Patients With Psychiatric Disorders: Violence Clues From Dogs.” Scientific Reports, vol. 9, no. 1, Nov. 2019.

World Health Organization: WHO. Anxiety Disorders. 27 Sept. 2023.

Team, Quality of Life. Measuring Progress, Well-being and Beyond GDP in the UK - Office for National Statistics. 27 May 2025.

Katsuyama, Masako, et al. “How Emotional Changes Affect Skin Odor and Its Impact on Others.” PLoS ONE, vol. 17, no. 6, June 2022, p. e0270457.