Page 180 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 8
again of familiar individuals (caretakers) or unfamiliar individuals. Bonobos did not show an attentional bias towards human expressions of emotions, even though in a control experiment using the same stimuli, humans did show this bias. Nevertheless, low power may explain the null findings in bonobos. In Experiment 3 using a heterogeneous human sample, we found that in contrast to bonobos, humans showed an attentional bias towards emotions of familiar, socially-close conspecifics. The findings of this study underline that an attentional bias for emotions is driven by factors that hold motivational relevance to the observer (i.e., socially-relevant characteristics such as the species of the expressor and social closeness) (Brosch et al., 2013). Importantly, it indicates continuity between the attentional mechanism (i.e., selective attention) underlying emotion processing in humans and bonobos, but also that attention to emotions may be most sensitive when the expressors of these emotions are conspecifics.
As we did not study whether humans have an attentional bias for emotions of bonobos, we attempted to close this knowledge gap in the study described in Chapter 3 (Figure 1i). Moreover, most research into emotion-biased attention in humans has used isolated facial expressions of emotion, thereby not fully appreciating the role that whole-body emotional expressions play in recognizing emotional expressions, as these whole-body expressions embedded in a scene can provide more context (Figure 1a, c) (Kret et al., 2013a). Additionally, many studies have looked only at specific age classes or homogeneous populations such as university students, which are not good examples for generalizing about humans (Henrich et al., 2010). We partially tackled these issues by examining how a more heterogeneous (i.e., non- university) group of human adults and children rate emotional scenes of humans as well as bonobos on valence and arousal, and by measuring their attentional bias towards these scenes. Overall, humans perceived emotional scenes of other humans to be similar to scenes of bonobos in terms of valence (positivity or negativity) and arousal (intensity). However, children misinterpreted the bared-teeth display as a positive expression.Humans also showed an attentional bias towards emotional scenes of both species, but the bias was strongest for human emotional scenes. These findings could suggest a shared evolutionary origin for emotional expressions and their perception (Kret et al., 2020), but also show that in humans, a learning component may be important for understanding emotional expressions by other species such as bonobos.
As a next step, we examined whether an attentional bias towards emotions in bonobos and humans does not only occur initially when early attentional mechanisms
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