Who's a clever boy: the average dog has a mental age of about two. But what are they really thinking?

The Guardian

26-04-2025

The thing that made me think my dog may be a genius was the word monkey. We'd developed a game where I'd hide her monkey toy – a sad, lifeless being, long lobotomised by my golden retriever puppy – and, when I asked her to find it, I realised she could differentiate the word monkey from other objects. A woman in the park had a similar story. On holiday in an unfamiliar cottage, she had misplaced the car keys. After hunting for them for over an hour, her dog, a border collie, overheard her and her husband talking about it, recognised the word 'keys' and immediately went and found them.
So maybe my dog, Rhubarb, isn't a genius after all. Dogs, says Vanessa Woods, director of the Puppy Kindergarten project at Duke University in North Carolina, US, and writer of several books including Puppy Kindergarten: The New Science of Raising a Great Dog, can know hundreds of words for objects. 'Over 1,000, probably,' she says. 'And actually it's more interesting than that, because they learn words the way children learn words, and that's not by repetition.' Psychology professor Juliane Kaminski showed back in 2004 that a dog called Rico (another border collie), could learn, as children do, by inference – he didn't need to know the name of a new toy, he could work it out by excluding the toys he did know the names of.
We share our homes (sometimes our beds) with them, but how much do we really know about what dogs think and feel? Whether chihuahua or husky, domestic dogs descended from wolves, but their behaviour, says Clive Wynne, psychology professor at Arizona State University and director of its Canine Science Collaboratory research lab, is 'substantially different. You can tame wolves, and they can be really affectionate. But taming wolves is quite challenging, whereas taming dogs is so easy that you hardly ever talk about 'taming' dogs.'
There are about 13 million dogs in the UK. In the US, there are about 90 million. 'Whereas there are only a few thousand wolves left [in the US],' says Wynne (in the UK, they're extinct). 'In a world that's totally dominated by human beings, living alongside human beings was a good choice. Dogs evolved capacities to find it easier to live with humans.' Some researchers think dogs have 'evolved special forms of cognition, what you could call special forms of intelligence, to make them better at understanding people,' but Wynne says he's sceptical about this idea. 'I take the view that [the higher capabilities] are almost entirely in the emotional domain.'
Dogs seem to be born with the ability to read human emotions, says Woods: 'Like in human babies, reading our thoughts and intentions seems to be one of the first cognitive skills that comes online in puppies.' The ability to read our body language, she says, is something 'that really not even our closest living relative, the great apes, have'.
Dogs are social animals, and are very tuned into the humans around them. 'They watch humans and they pick up cues from humans, because by being observant, they get an easy life,' says Daniel Mills, professor of veterinary behavioural medicine at the University of Lincoln. 'The more I study dog cognition, actually the less 'smart' I think dogs are. But they are incredibly observant, really fine-tuned, and so they tend to do very smart things because they're very good at making associations.'
If dogs are brilliant at reading humans, we are terrible at reading dogs. A recent study by Wynne and Holly Molinaro, his colleague at Arizona State University, showed that people interpreted a dog's emotions based on external situations, rather than 'reading' the behaviour of the dog itself. Researchers recorded videos of a dog in 'positive' and 'negative' scenarios, for example being offered a treat or being gently told off, and asked particpants to assess the dog's emotions. They then edited the videos to remove the external scenarios, showing just the dog's reaction. People who saw the edited videos assessed the dog's emotions differently to those who saw the dog's reaction in context. They even found that our own emotions affect how we read dogs – people who considered themselves happier before the test were more likely to rate the dog's emotion positively.
Charges of anthropomorphism have dogged canine researchers, including Stanley Coren, professor emeritus in the department of psychology at the University of British Columbia, and a dogfather of dog science. The prevailing idea that dogs have similar cognitive and emotional capabilities to a human toddler goes back to research Coren did in the 90s – but this bit of anthropomorphism is quite useful for our poor human brains to relate to.
Coren adapted tests used for human infants to research dogs' language-learning abilities. 'We found that the average dog has a mental age of between two and two-and-a-half years [in human terms],' he says, one of his dogs barking in the background. 'The super-dogs, the upper 20% in terms of intelligence, have a mental age of between two-and-a-half and three.' We can extrapolate this, he says, to other mental and emotional capabilities. 'If an average two-and-a-half-year-old is expected to have these abilities, then the first guess would be that a dog would have those abilities.'
Young children recognise when the number of objects they've been looking at changes; dogs do too. Coren says dogs can count up to five. Between the ages of one and three, a child will learn to respond to a pointing gesture. 'At about age two, the average child will know there's something interesting there, and will usually look in that direction.' Dogs will do the same. But, he says, 'wolves don't have that response, even if they've been reared with a human family'.
One area where dogs beat toddlers is memory. Think of how much you remember from when you were around two (probably nothing). 'However, dogs have a good memory and there are lots of examples,' says Coren. He recalls a colleague's dog that had previously been owned by the colleague's Czech father, who had taught the dog commands in his native language. The colleague inherited the dog when it was about 18 months old, and it lived with him and his English-speaking family. Around seven years later, when a relative from the Czech Republic visited, the dog still responded to commands in Czech.
In terms of emotions, Coren says that the average two-and-a-half-year-old human 'will have all of the basic emotions – fear, aggression, love, surprise and disgust, but complex social emotions like guilt don't show up until a child is about four'. Many dog owners will claim that they can instantly recognise their dog's 'guilty face' – and there are numerous pictures and videos online of dogs apparently looking remorseful – but this is anthropomorphism at work again, as a study by Alexandra Horowitz, an expert in canine cognition, has shown. 'Dogs don't feel guilt, and those expressions you see are really fear, because they know that when they see their owner and the evidence of their transgression, then bad things happen,' says Coren.
'What does it take to feel guilty?' asks Wynne. 'You have to know that there are rules in your society, and you need to know that you've broken the rules, and you need to know that you've been found out. That's layer upon layer upon layer, and dogs just don't have all of that. They can tell you're upset with them, but that's as far as it goes.'
So, do our dogs really love us, or just view us as a provider of resources? 'I think they do,' says Mills. 'They have an incredible loyalty to humans. But is it the same as the sort of love that the human shows them? No, I don't think so. I think it's probably a purer form.' Wynne says he doesn't use the word 'love' in his scientific research papers, but adds: 'I think that's a perfectly reasonable way to capture the nature of the bond between people and dogs – a nurturing, caring type of love.' Woods, who says '100% they love you', points to a 2015 study by Takefumi Kikusui, a professor of animal behaviour, and others at Azabu University in Japan. It showed that both dogs and their owners experienced a surge of oxytocin – the love and bonding hormone – when they gazed into each other's eyes. Some dogs, like some children, 'are more demonstrative than others,' says Woods. 'If a dog is not particularly tactile, they tend to make a lot of eye contact – they're 'hugging' you with their eyes.'
Why do they seem to like or dislike certain people, or other dogs? When Wynne introduced dogs at rehoming shelters to two women who looked similar and dressed alike, 'the dogs very rapidly developed strong preferences for one stranger over another, but we don't know why'. At my puppy training class, two dogs took an instant and mutual dislike to each other. 'Maybe it's learned associations,' says Mills. 'It's not uncommon that, as a puppy, they may have been bowled over by a labrador, so they don't now like big dogs.' It could be our fault – we misread their caution about a new experience as fear and jerked them back on the lead, thinking we were keeping them safe, 'so now they have a learned association between that type of dog or person and punishment'. There is also research, says Mills, around excluding group members who threaten the integrity of the pack. It may be that some dogs 'do not like certain other dogs because they don't want them to be part of their group'. Because they view them as undesirable in some way? 'Yes, or they think that they're a freeloader, or they think their group is very good at the moment and they're closely bonded, and they don't want somebody else potentially joining it.'
If my dog does love me as much as I love her, why then does she ignore me so often? Her absolute favourite thing to do is lull me into letting her off the lead in the park, then race off into the distance as soon as she spots another dog/squirrel/muddy puddle, with me running after her, shouting manically while she completely ignores me. Even when I ask her to do something at home, without distractions, she often deliberately ignores me. 'When you say 'deliberately', you've immediately interpreted her behaviour, and we do this effortlessly – that's part of the problem,' says Mills. 'We think we know what's going on in their heads and, actually, she's probably just interested in something else. She's not deliberately ignoring you, because that implies she's thinking about it and choosing an action. She's doing her own thing.'
Wondering what your dog is thinking about is probably futile. They can analyse situations, says Mills, but they aren't capable of abstract thought in the way we are. Rather than being able to plan ahead, 'they're capable of goal-directed behaviour, but again, it doesn't require complex thoughts – you just have to have, in your brain, some sort of model'.
What makes dogs happy? 'Being with you,' says Woods. 'I think the happiest dog is when they're spending quality time with their owners.' Wynne says he's always on the verge of writing a paper 'called 'What is a good life for a dog?', and I don't suppose for a moment that it's the same for every single dog.' Every dog he's ever known loved going for walks, but his new dog prefers to go for a ride in the car. 'Discover through experience what makes a good life for your dog.' Aside from the obvious things – food, water, shelter, security and veterinary care – Wynne says 'almost all dogs need strong emotional connections to the people they live with'. It's the reason he dislikes the term 'separation anxiety' because 'it makes it sound like the dog is wrong [to miss you]. It is not reasonable to leave dogs alone for six, eight, 14 hours a day.'
I write as Rhubarb, my 10-month-old golden retriever, is staring at me. Is she simply telling me she loves me, as Woods suggests, or is it because she thinks it's time to stop work and pay her some attention? I'll take it as the latter.