Dogs copy their owners' yawns
The study found this was particularly noticeable when the dogs were listening to the yawns of people they knew.
Scientists suggested the findings, presented at the National Ethology Congress in Lisbon, showed canines had empathy to human behaviours.
"These results suggest that dogs have the capacity to empathise with humans," said lead author Karine Silva, from the University of Porto, Portugal.
For their study, researchers selected 29 dogs that had lived with their owners for at least six months.
They recorded the owners yawning before playing it back to the pets, along with recordings of the yawn of a stranger.
The study said nearly half of all dogs yawned when they heard a recording of a human being making a yawning noise
But the results also found the dogs were five times more likely to yawn when they heard their owners' voices played back.