Page 70 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Chapter 3
Emotion perception task
Adult participants were asked to rate the valence and arousal of the human (n = 126) and bonobo (n = 467) pictures on 1–7 rating scales (1 being negative or low arousing; 7 being positive or high arousing). Children used the Self-assessment manikin (line drawing of a cartoonish human figure with a facial expression ranging from very negative to very positive Lang, 1980).
Emotional dot-probe task
Based on the scores of the emotion perception task, we selected 10 scenes per emotional category that were a) best recognized regarding valence and b) most emotionally arousing. The selected pictures were used as stimuli in the human-scene dot-probe task. For the bonobo-scene dot-probe task, stimuli were selected using the validation data of experts gathered during previous studies with bonobos (Kret et al., 2016; Van Berlo et al., 2020a).
During the dot-probe task, a trial started with the presentation of a black dot centered horizontally in the lower quadrant of the display that remained visible until response (i.e., tapped) (see Figure 3). Following a response, two images (emotional vs. neutral) were simultaneously presented on the left and right quadrants of the display (50% chance) for 300 ms and replaced by a black dot either on the left or right location of the display (50% chance). Every trial ended with an inter-trial interval (ITI) of 2,000 ms. The location of the dot and stimuli were balanced. Trials were presented in a pseudo-randomized manner. There were two different versions of the bonobo scene dot-probe task. Version 1 included 45 trials and Version 2 (which had one
Figure 3. Trial outline of the dot-probe.
68