Page 45 - Emotions through the eyes of our closest living relatives- Exploring attentional and behavioral mechanisms

Emotional attention is modulated by familiarity
contained only two different neutral expressions per model, for the unfamiliar stimuli only the emotional pictures were all unique.
To check the validity of our stimulus materials, we first asked an independent
group of research assistants (N = 5) to rate the materials on emotion type (whether 2 the stimulus is an emotional or neutral expression), arousal and authenticity. Results
indicated the following intraclass correlations: intensity of the stimuli (ICC = .78),
emotion (ICC = .66), and authenticity (ICC = .69; see Tables S5.1 and S5.2).
Figure 5. Examples of the stimuli of emotional and neutral expressions. The NimStim models (not depicted here) were females 1, 2, 3, and 7, 8, 9 (Tottenham et al., 2009). An emotional picture was always paired with a neutral picture, and these pictures were always either from the NimStim or Keeper stimulus set.
Procedure
The procedure for bonobos in Experiment 2 was similar to Experiment 1, except that the stimuli in Experiment 2 consisted of the six human basic emotional facial expressions (Figure 3). The reason for using facial expressions rather than scenes was based on two considerations. First, previous dot-probe studies in humans have mainly used facial expressions to examine attentional bias (Van Rooijen et al., 2017), thus allowing us to compare the results of Experiment 2 to existing findings. Second, it would not have been possible to get some of the emotional scenes (e.g., play, grooming, sex) from the familiar people. On average, each bonobo finished 345 trials (SD = 24.56), divided over 13-15 sessions per individual (Table S6).
Data Filtering
As in Experiment 1, two experts rated the videos in high agreement (ICC = .96, p < .001). We used the same data filtering criteria as in Experiment 1, resulting in removal of 373 trials (27.1%, Table S6).
Statistical analyses
Similar to Experiment 1, we used a GLMM with a nested structure with trials (25) nested within sessions (13-15) nested within participants (ID, 4) and random
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