Contagious yawning: a reflection of empathy, mimicry, or contagion?

Yawning is a curious behavioural phenomenon that at times may be described as ‘contagious’, appearing to spread from one individual to another. Contagious yawning is seen in several primate species, including humans (Provine 1986; Baenninger 1997; Campbell et al. 2009; Palagi et al. 2009). Here we argue that contagious yawning, particularly the newly documented phenomenon of cross-species contagious yawning (JolyMascheroni et al. 2008), is an important avenue of research. In the discussion that follows, we hope to encourage further experimentation to identify the possible functions of and mechanisms underlying contagious yawning. Yawning has several convenient properties that make it ideal for cross-species research. First, it is already in the behavioural repertoire of a broad spectrum of vertebrates, from fish to birds to mammals (Baenninger 1997; Gallup et al. 2009). Thus, cross-species comparisons do not hinge on complex and error-prone training protocols. Because it occurs spontaneously at low frequency, crossindividual yawning in a temporally correlated but asynchronous way is easy to detect and difficult to explain as chance. Our principal interest in cross-species contagious yawning is its potential link with social cognitive capacities. As described in a recent report by Joly-Mascheroni et al. (2008), 21 of 29 pet dogs, Canis familiaris, tested yawned after seeing human yawns while none yawned after seeing silent mouth openings. A prominently raised hypothesis in Joly-Mascheroni et al. (2008, page 447) is that ‘contagious yawning of dogs may relate to their capacity for empathy’. This intriguing hypothesis is also proposed in findings of contagious yawning in nonhuman primates (Palagi et al. 2009) and as explaining the relative lack of contagious yawning in autistic children (Senju et al. 2007). Empathy is notoriously difficult to define (Preston & de Waal 2002). While empathy is not defined in Joly-Mascheroni et al. or Palagi et al., and can be construed in many ways, a related letter (Senju et al. 2007) cites two references that both offer high-level definitions for the term. One refers to empathy as ‘the capacity to predict and to respond to the behavior of agents (.) by inferring their mental states’ (Baron-Cohen et al. 2005, page 819), and the other refers to contagious yawning as ‘a consequence of a theory of * Correspondence: J. M. D. Yoon, Department of Psychology, Stanford University, Stanford, CA 94305, U.S.A. E-mail address: [email protected] (J.M.D. Yoon). 1 Equal contributions. 2 C. Tennie is at the Department of Developmental and Comparative Psychology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, D-04103 Leipzig, Germany.