Page 132 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 6
2020; Norscia & Palagi, 2011a; Palagi et al., 2009; Platek et al., 2003; Romero et al., 2013). Indeed, neuroimaging studies have shown increased brain activity during CY in areas involved in theory of mind and social cognition (Cooper et al., 2012; Haker et al., 2013; Platek et al., 2005), corroborating the idea that CY is linked with emotional state-matching and perhaps even empathy.
Furthermore, individuals who score low on empathy scales (e.g., individuals on the autism spectrum) are less likely to show CY (Senju et al., 2007), and females yawn more frequently in response to seeing others yawn than males do, reflecting the idea that females show higher levels of empathy than males because of their investment in offspring care (Norscia et al., 2016a). Nevertheless, there are some studies that do not find such a clear link between CY and empathy. For instance, when people with autism spectrum disorder (ASD) are instructed to pay attention to the eyes (avoidance of the eyes is one of the characteristics of ASD), they are just as likely to yawn contagiously as neurotypical individuals (Usui et al., 2013). Furthermore, the gender bias is not consistently found (e.g., Bartholomew & Cirulli, 2014; Massen et al., 2012) and heavily debated (Gallup & Massen, 2016; Norscia et al., 2016a). For instance, in chimpanzees, it appears that males yawn more frequently than females in response to seeing other males yawn (Massen et al., 2012). Finally, while dogs do engage in CY, its presence is not affected by whether the yawner is prosocial versus the yawner being antisocial (Neilands et al., 2020). The mixed findings in the studies investigating the relationship between CY and a complex construct such as empathy show that the topic deserves more attention, and that it is still debated (see Massen & Gallup, 2017, for a critical review).
The emotional bias hypothesis is a more detailed specification of how CY can be socially modulated through a shared PAM, namely via social closeness and familiarity. The hypothesis predicts that individuals who are socially, and thus emotionally close are also more likely to yawn contagiously in response to each other (Demuru & Palagi, 2012; Hatfield et al., 1993; Palagi et al., 2004, 2014; Romero et al., 2013, 2014; Silva et al., 2012). Additionally, individuals from a group (i.e., familiar others) are more likely to yawn in response to each other than to unfamiliar others (Campbell & de Waal, 2011; Romero et al., 2013). A potential issue that has been raised is that these studies often fail to rule out simple alternative explanations for CY that do not require higher-order cognition (Massen & Gallup, 2017). For instance, effects of familiarity on CY may be explained by a general tendency to bias attention to familiar and socially close others (Massen & Gallup, 2017). Nevertheless, in a recent study investigating auditory yawn contagion in humans, yawns were most contagious between family
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