Page 168 - Demo

Chapter 7166Experiment 2Replication first fixation Similar to Experiment 1, the outcomes of the Bayesian binary logistic regression (Supplementary Table 1) suggested that the orang-utans had a first fixation bias towards flanged male stimuli (bIntercept = 0.582 [0.039], 89% CrI [0.520; 0.645], pd = 0.981). Although all individuals showed a bias in the expected direction, the finding was not robust for all four orang-utans (Figure 2A) Amos (bIntercept = 0.596 [0.057], 89% CrI [0.504; 0.694], pd = 0.955) and Sandy (bIntercept = 0.601 [0.057], 89% CrI [0.509; 0.698], pd = 0.963) showed a more robust first fixation bias than Samboja (bIntercept = 0.585 [0.056], 89% CrI [0.489; 0.678], pd = 0.925) and especially Wattana (bIntercept = 0.549 [0.064], 89% CrI [0.436; 0.648], pd = 0.756). In addition, we again found that the orang-utans had a leftward bias (bleft-right = 0.195 [0.072], 89% CrI [-0.079; 0.309], pd = 0.997), although it was less pronounced than in Experiment 1.Replication total fixation durationSimilar to Experiment 1, the outcomes of the Bayesian zero-one inflated beta regression (Supplementary Table 2) suggested that the orang-utans had an attentional bias towards flanged male stimuli (bIntercept = 0.607 [0.028], 89% CrI [0.564; 0.653], pd = 1.000). However, in contrast to Experiment 1, all four orangutans had a robust bias towards flanged males (Figure 2B): Amos (bIntercept = 0.593 [0.032], 89% CrI [0.541; 0.645], pd = 0.997), Samboja (bIntercept = 0.597 [0.036], 89% CrI [0.540; 0.656], pd = 0.995), Sandy (bIntercept = 0.625 [0.054], 89% CrI [0.542; 0.715], pd = 0.991), and Wattana (bIntercept= 0.613 [0.048], 89% CrI [0.526; 0.690], pd = 0.978). Furthermore, similar to Experiment 1, we found no side bias (bIntercept = 0.002 [0.049], 89% CrI [-0.073; 0.085], pd = 0.519).Full dataset With regard to the first fixation duration, we found that probability of first fixation on the left stimulus depended on the combination of stimuli (Supplementary Table 3; Figure 3A; see Appendix G for model stability checks). First, in line with our previous analyses, the orang-utans had an overall left bias for first fixation (b = 0.604 [0.029], 89% CrI [0.558; 0.651], pd = 1.000). Second, we found a difference in probability of first fixation on the left stimulus between trials where a flanged male was presented on the left with an unflanged male on the right, and an unflanged male on the left with a flanged male on the right (bFM.UFM-UFM.FM = 0.164 [0.063], 89% CrI [0.064; 0.263], pd = 0.996). However, probability of fixating on the left stimulus first did not differ robustly between any of the other conditions (Supplementary Table 5).Tom Roth.indd 166 08-01-2024 10:42