That "guilty look" on a dog's face is all in the imagination of the human owner, suggests research.
Dog owners have often claimed they can read the expressions of their pets - particularly that tell-tale look when they have done something wrong.
But researchers at a New York college tricked owners into thinking innocent pets had misbehaved - with the owners still claiming to see this guilty look.
The study found that the expression had no relation to the dogs' behaviour.
And researchers found that pet owners' belief that they could read their dogs' "body language" was often entirely unfounded.
Stolen treats
The study from Alexandra Horowitz, assistant professor at Barnard College in New York, showed that owners were projecting human values onto their pets.

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The research, Canine Behaviour and Cognition, looked at how dog owners interpreted their pets' expressions, when they believed that the dog had stolen and eaten a forbidden treat.
In a series of tests, owners were sometimes given accurate and sometimes false information about whether their dog had stolen the treat.
But the research, published in Behavioural Processes, found that owners' interpretations of whether their dog looked guilty bore no reliable link with whether the dog had really stolen the treat.
When the owners had been told their dog had misbehaved, they saw this guilty expression, even when the dog had not really done anything wrong.
Where there was any change in the dogs' expression, it was seen to be a subsequent reflection of the human's emotions.
If an owner thought the dog had misbehaved and then told the dog off, some dogs showed an "admonished" look, which humans then misunderstood as an admission of guilt.
The dogs which were most likely to "look guilty", according to their owners, were those who were entirely innocent and had then been told off by owners who believed that they had stolen treats.
Researchers concluded that any such "guilty look" is a response to human behaviour and has no relation with the dog's actions or sense of having broken any rules.