Page 18 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 1
as the general tendency to live on their own, likely has a close link to the availability of fruit, with fruit scarcity leading to less association, and fruit abundance to more social interactions (Roth et al., 2020). Cognitive research on orangutans has gained more traction in the last decade (Damerius et al., 2019; Hopper, 2017), but almost no work has looked at how orangutans perceive emotional expressions, and how their socio-cognitive abilities compare to the other apes and humans. Their unique semi- solitary nature may therefore provide interesting insights into the development of these capacities over evolutionary time.
Enhanced attention for emotions
One of the earliest processes involved in emotion processing is attention (Figure 1i). Attention is the gatekeeper that selectively filters relevant from irrelevant information coming from the environment (James, 1890). This process is crucial, as the brain cannot attend to all information at once. Remarkably, already at the very early stages of processing information from the environment, attention automatically and efficiently tunes to emotionally salient signals (Whalen, 1998). Indeed, a large body of evidence stemming from human studies has shown that emotions are so fundamental to our species, that our brains evolved sensory mechanisms that preferentially process emotional information over other, more neutral signals (Phelps & LeDoux, 2005). Especially negative emotions (for instance fear or anger) appear to strongly capture our attention. From an evolutionary perspective, this makes a lot of sense. Perceiving anger or fear in others could mean that there is imminent danger, requiring immediate action from the observer. Early studies on this so-called implicit attentional bias for threatening signals, showed that humans automatically attend to threatening stimuli such as snakes, spiders, or angry faces (Öhman et al., 2001a), and suggested the brain and especially its emotion center (including subcortical structures such as the amygdala) is “hard-wired” to detect such threats in the service of evolutionary goals (Öhman et al., 2007).
New research suggests that parts of the brain’s emotion centers are not just hard- wired threat detectors, but are highly sensitive to motivationally relevant emotional signals (Cunningham et al., 2008). Indeed, enhanced attention to negatively- or positively-valenced emotions appears to differ between individuals, across developmental trajectories and the age spectrum (Todd et al., 2012), and is affected by an individual’s current affective state (Mendl et al., 2009). This also may explain why highly anxious individuals show a particularly strong bias towards angry or fearful faces (Bar-Haim et al., 2007). Moreover, allocation of attention to emotional stimuli
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