Dogs can tell when people are lying to them, study finds

A team of researchers at the University of Vienna has found that dogs can sometimes tell when people are lying to them. In their paper published in Proceedings of the Royal Society B, the group describes experiments they conducted with hundreds of dogs, and what was learned about their ability to detect deception in unknown people.

Adult humans have been found to engage in mental state assessments of others. People determine, based on various clues, the truthfulness of other people, for example. In this new effort, the researchers wondered if the same might be true of dogs. To find out, they carried out simple experiments with 260 dog volunteers of various breeds.

In the experiments, all of the dogs were taught to follow the advice of an unknown human in choosing which of two bowls contained a hidden treat. By following the advice, they received the treat. Then the researchers mixed things up. They allowed the dogs to watch as another unknown human moved the treat from one bowl to another while a second unknown human watched; in other cases, the second human was absent from the switch-up. The researchers then conducted the same experiments with the dogs and the second person in the switch-up to see if the dogs would continue to follow the advice.

The researchers found that the dogs ignored the human advice if the person had not been present when the bowls were switched—they knew the person did not know which bowl had the treat. But more importantly, half of the dogs ignored the human advice when they knew from observation that the human was pointing at the wrong bowl—evidence indicating that the dogs knew the humans were lying to them.

As an aside, the researchers noted that the same experiments had been carried out by prior researchers with humans under the age of five, macaques and chimpanzees. In those experiments, the children and the other animals were much more likely than the dogs to follow the advice of the obvious liar over what they knew to be true. They suggest this indicates that the dogs were less trusting of the unknown human giving the advice.