New research on dogs' brains has thrown light on why the animals can seemingly share emotions with people.
By placing the animals in a scanner, researchers from Hungary found that dogs' brains react to voices in the same way that the human brain does -- especially when they hear emotionally charged sounds, such as laughter.
The researchers say this might explain why the animals seem so attuned to humans' feelings.
The work is published in the journal Current Biology.
Lead author Attila Andics, from the Hungarian Academy of Science's Eotvos Lorand University in Budapest, said: "We think dogs and humans have a very similar mechanism to process emotional information."
Lots of praise
Eleven pet dogs took part in the study; training them took some time.
"We used positive reinforcement strategies - lots of praise," said Dr Andics.
"There were 12 sessions of preparatory training, then seven sessions in the scanner room, then these dogs were able to lie motionless for as long as eight minutes. Once they were trained, they were so happy, I wouldn't have believed it if I didn't see it."
For comparison, the team looked at the brains of 22 human volunteers in the same MRI scanners.
The scientists played the people and pooches 200 different sounds, ranging from environmental noises, such as car sounds and whistles, to human sounds (but not words) and dog vocalisations.
The researchers found that a similar region - the temporal pole, which is the most anterior part of the temporal lobe - was activated when both the animals and people heard human voices.
"We do know there are voice areas in humans, areas that respond more strongly to human sounds that any other types of sounds," Dr Andics explained.
"The location (of the activity) in the dog brain is very similar to where we found it in the human brain. The fact that we found these areas exist at all in the dog brain at all is a surprise - it is the first time we have seen this in a non-primate."