Page 49 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Emotional attention is modulated by familiarity
are sensitive to emotional expressions of another, phylogenetically close species.
Possibly, differences in methodology may explain why we did not find an emotion
bias. The dot-probe has very short exposure times, likely tapping into an early
attentional process (MacLeod et al., 1986), whereas longer stimulus exposure (such 2 as in the studies by Kano & Tomonaga (2010b) and Pritsch et al. (2017)) can provide
additional information to the observer and recruit prior knowledge and experiences to process what is seen.
Finally, although the expressions were salient enough for humans to reveal an attentional bias towards these expressions in our control experiment, they may simply not have been salient for bonobos. This is difficult to quantify; though the stimuli were rated on valence and intensity, they were of course rated by humans and not bonobos. Moreover, our data may not have had sufficient power to detect an effect. It is therefore difficult to draw a definitive conclusion on attentional biases for emotions of humans. A potential future direction could be to test immediate and sustained attention for familiar and unfamiliar humans, and subsequently test a possible interaction with emotions. Furthermore, a matching-to-sample task could be useful to study whether bonobos can distinguish between human expressions of emotion.
Experiment 3: Humans’ attentional bias towards emotions of familiar and unfamiliar conspecifics
Method
Participants
We recruited pairs of individuals to be either taking part in the dot-probe task or to be on the photographs used for the familiar stimuli. Participants thus consisted of those partaking in the dot-probe task (N = 449, 253 women), or were the to-be photographed companions (N = 406, 208 men. For 43 companions, data on sex and age were missing due to a technical malfunction). Participants were adults and children (Dot probe participants: 262 adults, 187 children. Companions for the photos: 218 adults, 188 children) visiting Apenheul. Dot probe participants were between 3 and 84 years old (M = 24.9, SD = 16.43), and companions were between the ages 3 to 79 (M = 25.43, SD = 17.22). Apenheul allowed us to set up a research corner close to the bonobo enclosure where we could test the visitors (Figure 6). As bonobos were only exposed to group members (kin and friends) in familiar trials, our human
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