Absence of contagious yawning in children with autism spectrum disorder

This study is the first to report the disturbance of contagious yawning in individuals with autism spectrum disorder (ASD). Twenty-four children with ASD as well as 25 age-matched typically developing (TD) children observed video clips of either yawning or control mouth movements. Yawning video clips elicited more yawns in TD children than in children with ASD, but the frequency of yawns did not differ between groups when they observed control video clips. Moreover, TD children yawned more during or after the yawn video clips than the control video clips, but the type of video clips did not affect the amount of yawning in children with ASD. Current results suggest that contagious yawning is impaired in ASD, which may relate to their impairment in empathy. It supports the claim that contagious yawning is based on the capacity for empathy.     

Chimpanzees empathize with group mates and humans,but not with baboons or unfamiliar chimpanzees

Human empathy can extend to strangers and even other species, but it is unknown whether non-humans are similarly broad in their empathic responses. We explored the breadth and flexibility of empathy in chimpanzees, a close relative of humans. We used contagious yawning to measure involuntary empathy and showed chimpanzees videos of familiar humans, unfamiliar humans and gelada baboons (an unfamiliar species). We tested whether each class of stimuli elicited contagion by comparing the effect of yawn and control videos. After including previous data on the response to ingroup and outgroup chimpanzees, we found that familiar and unfamiliar humans elicited contagion equal to that of ingroup chimpanzees. Gelada baboons did not elicit contagion, and the response to them was equal to that of outgroup chimpanzees. However, the chimpanzees watched the outgroup chimpanzee videos more than any other. The combination of high interest and low contagion may stem from hostility towards unfamiliar chimpanzees, which may interfere with an empathic response. Overall, chimpanzees showed flexibility in that they formed an empathic connection with a different species, including unknown members of that species. These results imply that human empathic flexibility is shared with related species.     

Dogs catch human yawns

This study is the first to demonstrate that human yawns are possibly contagious to domestic dogs (Canis familiaris). Twenty-nine dogs observed a human yawning or making control mouth movements. Twenty-one dogs yawned when they observed a human yawning, but control mouth movements did not elicit yawning from any of them. The presence of contagious yawning in dogs suggests that this phenomenon is not specific to primate species and may indicate that dogs possess the capacity for a rudimentary form of empathy. Since yawning is known to modulate the levels of arousal, yawn contagion may help coordinate dog-human interaction and communication. Understanding the mechanism as well as the function of contagious yawning between humans and dogs requires more detailed investigation.     

Yawning: An evolutionary perspective

Yawning is a ubiquitous activity among humans, nonhuman primates, mammals, birds and other vertebrates. Comparative analysis suggests that yawning has two major features: (1) communication — whereby the behavior of other individuals is affected, and (2) direct physiological benefit — whereby the organism is receiving some direct physiological benefit from yawning. Various functional hypotheses used to explain yawning in an evolutionary context are reviewed. The contagious nature in humans and the manifest lack of contagion in other species suggests that yawning in humans has a different and as yet poorly understood evolutionary history.     

Food-reinforced yawning in Macaca tonkeana

An operant conditioning paradigm comprising continuous food-reinforcement, fixed-ratio responding, and extinction procedures was used to evaluate the possibility that adult male macaques can control their rate of yawning. Two non-food-deprived Macaca tonkeana quickly learned to produce yawns for food rewards. They also increased the rate of production according to fixed-ratio requirements, and showed initial response peaks followed by diminished rates of yawning during extinction. The results indicate that adult male macaques can yawn voluntarily. Further work along these lines may help distinguish among different types of yawning as indicated in the literature.