Do you get tired when others yawn（哈欠）? Does your dog get tired when you yawn? New research from Lund University in Sweden establishes that dogs catch yawns from humans. But not if the dogs are too young. The study, published in Springer's journal Animal Cognition, found that, like humans, dogs show a developmental trend in susceptibility to contagious¹ yawning. While dogs above seven months of age catch human yawns, younger dogs are immune to yawn contagion²（传染病）. Contagious yawning is not just a sign of sleepiness or boredom³. Previous research has shown contagious yawning in humans, adult chimpanzees, baboons⁴ and dogs, and suggests that it can be used as a measure of empathy. Empathy, mimicking⁵ the emotional responses of others, is difficult to measure directly, but contagious yawning allows assessment⁶ of a behavioral empathetic response, the researchers say.

 

While the development of contagious yawning in human children has seen much research, this is the first study to investigate its development in another species.

 

Elainie Alenkær Madsen, PhD, and Tomas Persson, PhD, researchers at Lund University, engaged 35 dogs in Denmark, aged⁷ between four and 14 months, in bouts⁸ of play and cuddling and observed the dogs' responses when a human repeatedly yawned or gaped⁹ or performed neither of the two expressions. Only dogs above seven months of age showed evidence of contagious yawning.

 

This pattern of development is consistent with that in humans, who also show a developmental increase in susceptibility to yawn contagion, with children typically beginning to yawn contagiously¹⁰ at the age of four, when a number of cognitive¹¹ abilities, such as accurate identification of others' emotions, begin to clearly manifest. One interpretation¹² that Madsen and Persson suggest is that the results reflect a general developmental pattern, shared by humans and other animals, in terms of affective empathy and the ability to identify others' emotions. Given that contagious yawning may be an empathetic response, the results suggest that empathy and the mimicry¹³（模仿） that may underlie¹⁴ it develop slowly over the first year of a dog's life.

 

There was some evidence that the researchers may have transferred the emotion that yawning reflects (sleepiness) to the dogs, as nearly half of the dogs responded to yawning with a reduction in arousal（觉醒，激励）, to the extent that the experimenter needed to prevent a number of dogs from falling asleep.

 

Research with adult humans and other primates¹⁵ suggest that individuals are more likely to yawn contagiously to those with whom they have close emotional bonds. Madsen and Persson tested the dogs with both an unfamiliar¹⁶ experimenter and their owner, but found no evidence that the puppies preferentially yawned in response to the yawns of the human with whom they were emotionally close. Since this is also the case for young human children, the researchers suggest that in species that show an empathy-based social modulatory effect on contagious yawning, this behavior only emerges at later stages of development.

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