Researchers at Lund University, writing in the journal Animal Cognition, report a developmental, age-related trend in susceptibility to contagious yawning seems to operate in both humans and dogs.
Previous research has demonstrated contagious yawning in humans, adult chimpanzees, baboons and dogs, and suggests it is evidence of empathy.
The researchers studied 35 dogs between 4 and 14 months of age in bouts of play and cuddling with humans and observed the dogs' responses when people repeatedly yawned, finding only dogs older than 7 months showed evidence of contagious yawning.
A similar pattern exists in humans, researchers said, with children typically beginning to yawn contagiously at age 4 when a number of cognitive abilities begin to show.
The results suggest a general developmental pattern, shared by humans and other animals, in terms of affective empathy and the ability to identify others' emotions, they said.