Humans, chimps and other primates have all been shown to be susceptible to contagious yawning. Previous research has suggested that dogs are, too, unless — according to newly published findings — that dog is a puppy younger than seven months.
In what sounds like the most adorably awesome study ever devised, researchers Elainie Alenkær Madsen and Tomas Persson watched what happened when 35 puppies, aged between 4 and 14 months, were exposed to yawning humans. Puppies were presented with a combination of experimental conditions. They played with people they were familiar with, but also with strangers. Humans were instructed to deliver convincing yawns (complete with the groans, breathing noises and body movements often associated with yawning), and far-less theatrical "mouth gapes," which involved simply opening one's mouth.
Dogs were found to yawn contagiously, but only if they were older than seven months. What's more, a dog's relationship with its yawning human appeared to have no affect in the strength of contagion.
Interestingly, the results actually mirror the findings of studies on yawn-contagion in humans children, who typically become susceptible to contagious yawning around age four.
"The results support the notion of a developmental increase in dogs' attention to others and identification of others' emotional states," note the researchers, "and suggest that yawn contagion is underpinned by developmental processes shared by humans and other animals."
The researchers' findings are published in the latest issue of Animal Cognition.