Page 34 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 2
Additionally, we define expressions of emotions descriptively (Paul & Mendl, 2018) and broadly as visually observable facial and/or body expressions that often occur in social interactions, and that can differ in terms of valence and arousal (Russell, 1980). Based on these definitions, we investigate whether bonobos have an attentional bias towards emotional expressions of unfamiliar and familiar conspecifics (Experiment 1), followed by whether this bias extends to unfamiliar and familiar human expressions (Experiment 2). In Experiment 3, using a large community sample of zoo visitors, we investigate whether attention is attuned to emotional expressions of familiar (family and friends also visiting the zoo) or unfamiliar (other zoo visitors) people.
We hypothesize that bonobos, due to their xenophilic tendencies, will show an attentional bias towards emotions expressed by unfamiliar conspecifics (Kret et al., 2016) and that a similar bias will be dampened when seeing familiar conspecifics. Furthermore, since certain aspects of emotion processing are shared between humans and extant apes (Kret et al., 2020), we further predict that bonobos will show an attentional bias towards emotional expressions of humans. Whether this bias is modulated by the familiarity of the human expressor is an exploratory question. For humans, we hypothesize that an attentional bias towards emotions exists for expressions of unfamiliar individuals, in line with established findings (Van Rooijen et al., 2017). We also expect that this bias will be more pronounced for familiar individuals as compared to unfamiliar individuals, reflecting the more in-group focused, parochial tendencies of humans (Bowles, 2009).
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