Familiarity Bias and Physiological Responses in Contagious Yawning by Dogs Support Link to Empathy

Abstract

In humans, the susceptibility to yawn contagion has been theoretically and empirically related to our capacity for empathy. Because of its relevance to evolutionary biology, this phenomenon has been the focus of recent investigations in non-human species. In line with the empathic hypothesis, contagious yawning has been shown to correlate with the level of social attachment in several primate species. Domestic dogs (Canis familiaris) have also shown the ability to yawn contagiously. To date, however, the social modulation of dog contagious yawning has received contradictory support and alternative explanations (i.e., yawn as a mild distress response) could explain positive evidence. The present study aims to replicate contagious yawning in dogs and to discriminate between the two possible mediating mechanisms (i.e., empathic vs. distress related response). Twenty-five dogs observed familiar (dog’s owner) and unfamiliar human models (experimenter) acting out a yawn or control mouth movements. Concurrent physiological measures (heart rate) were additionally monitored for twenty-one of the subjects. The occurrence of yawn contagion was significantly higher during the yawning condition than during the control mouth movements. Furthermore, the dogs yawned more frequently when watching the familiar model than the unfamiliar one demonstrating that the contagiousness of yawning in dogs correlated with the level of emotional proximity. Moreover, subjects’ heart rate did not differ among conditions suggesting that the phenomenon of contagious yawning in dogs is unrelated to stressful events. Our findings are consistent with the view that contagious yawning is modulated by affective components of the behavior and may indicate that rudimentary forms of empathy could be present in domesticated dogs.

Rudimentary empathy in macaques’ social decision-making

“…Our finding of similar, and correlated behavioral responses to the direct experience of an aversive stimulus and to the observation of its impact upon a peer would appear consistent with simulation theories of empathy (7)(8)(9)21). Empathic-like responses have already been reported in others animal studies (2,5,7,(53)(54)(55)(56). Such behavioral responses are usually either contagious, modulated by past experience, and/or dependent on the partner identity.…”

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

“…The difference in response to the gelada baboon yawn and control videos was non-significant, however (t 18 figure 1). Incorporating previous data on the response to ingroup versus outgroup chimpanzees [13] allows us to compare yawning rates across the five classes of video.…”

“…mean of outgroup chimpanzee and gelada baboon). We compared these means using a paired-sample t-test and found a significant difference (t 18 …”

“…There are now studies of empathy in mammals, from mice (Mus musculus) [2], rats (Rattus norvegicus) [3] and dogs (Canis lupus familiaris) [4] to elephants (Loxodonta africana) [5], and also in birds [6,7]. One common behavioural measure is contagious yawning (CY), which appears to fit the empathy framework because of four key findings: (i) human adults high on other measures of empathy show more CY [8]; (ii) humans with developmental and personality disorders in which empathy is impaired show diminished CY [8][9][10][11]; (iii) CY is positively biased by familiarity in humans (Homo sapiens) [12], chimpanzees (Pan troglodytes) [13], bonobos (Pan paniscus) [14], gelada baboons (Theropithecus gelada) [15] and dogs [16][17][18], as is typical of other measures of empathy; and (iv) presented with a variety of body movements apes exclusively increase yawning in response to observed yawning, suggesting CY's high specificity [19,20]. Aiding this specificity, brain areas associated with the human mirror neuron system activate in humans viewing yawns [21][22][23], with mirror neurons having been implied as a proximate neural mechanism for empathy [24,25].…”

Oxytocin promotes social bonding in dogs

“…Although some animals may form permanent cross-species associations (26), marked preferences for particular individuals of another species are not common (27). Through cohabitation with humans, dogs are able to establish close bonding and attachment with people (21, 28), which in turn may modulate their behavioral and emotional responses (28,29). Here we show that the same neurological mechanisms implicated in the regulation of intraspecific bonds in mammal also modulate cooperative associations between individuals from different species, suggesting that this hormonal mechanism might underlie the formation of stable cooperative associations between genetically unrelated individuals.…”