Clearly, dogs are quite good at understanding us. But how far does this go and how are they able to understand our emotions – what cues are they reading?
A dog who has lived among people is a much better reader of us than we are of them (or, one might suggest, of ourselves). In a way, dogs are anthropologists: they spend a lot of time observing us and thus learn associations between behaviours we might not know about ourselves.
In the home, you might see this in their learning to predict the difference between you getting up to take them out and getting up to go to the fridge.
From studies with owned dogs, we also know that they can read stress and even detect fear, and they can identify the presence of diseases that we don’t know we have. Part of their skill is due to their acute sense of smell, but, despite not being bipedal and having no hands, dogs know about our bodies.
When interpreting others’ feelings, we tend to focus on peoples’ heads (and on dogs’ heads, too). They read our faces, as well.
Several studies into how dogs perceive human emotional expressions found that they’re good at distinguishing happy human faces from faces with blank expressions and happy faces from angry ones, and can even match a photo of a happy or angry face with a vocalisation in the same emotional tone.
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They can use a person’s facial expression when opening a box (a look of delight or disgust) to choose if they want to approach that box themselves. And they can identify these expressions even when presented with a photo of only the top half of the face (so even if that face is hidden by a COVID mask).
They know our voices (they can match a stranger's voice to their gender, and recognise their person’s voice) and they know our smells (they recognise their own person’s odour on a t-shirt and distinguish it from a stranger’s odour).
Recently, researchers have confirmed the claim that dogs recognise fear: they’re able to discriminate t-shirts containing the odour of someone who was afraid (watching a scary movie) from those from someone watching something more benign.
They can also certainly see our fear, and stress, in our changed body language. One study even found a correlation between the testosterone level of a person (depending on whether their sports team won or lost) and the dog’s cortisol, or stress, level.
Through studying thousands of hours of human behaviour from their side of the living room, dogs come to know our minds.
For instance, one study found that dogs know when we’re doing something intentionally (such as putting something desirable out of their reach) or unintentionally (such as accidentally dropping something desirable out of their reach) and will behave differently when the action is unfriendly or just clumsy.
Several studies have confirmed they know that if we’re not in the room with them – or just turned away – they can get away with eating something they’ve been forbidden from eating. But they also recognise when our noses are glued to a book or our eyes are glued to a computer as indications that they can also get away with eating it, sooner than if our eyes are on them.
More broadly, they think about knowledge states: dogs distinguish people who are knowledgeable and ignorant about the source of hidden food, recognising that if someone wasn’t in the room when it was hidden, their gestures about where to find it are not worth following.
Finally, and most impressively, they can smell our illness. From the very first reports of pet dogs who identified melanomas on their people (annoyingly biting and scratching at parts of the owners’ bodies), several teams of researchers have been at work training dogs who can, now, identify various cancers by smell, alert a diabetic when their blood sugar rises precipitously, and even smell COVID.
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