Page 167 - Demo

Eye-tracking reveals bias to flanges in orang-utans1657Total fixation durationThe outcomes of the Bayesian zero-one inflated beta regression (Supplementary Table 2; see Appendix G for model stability checks) suggested that the orangutans had an attentional bias towards flanged male stimuli (bIntercept= 0.575 [0.024], 89% CrI [0.538; 0.615], pd = 0.999). Again, this was not the case for all individuals (Figure 1B): for Amos (bIntercept = 0.596 [0.038], 89% CrI [0.536; 0.656], pd = 0.996) and Wattana (bIntercept = 0.608 [0.040], 89% CrI [0.544; 0.671], pd = 0.997) we found a clear bias. For Sandy it was less pronounced (bIntercept = 0.574 [0.046], 89% CrI [0.498; 0.645], pd = 0.942), whereas Samboja showed no clear bias (bIntercept = 0.525 [0.046], 89% CrI [0.449; 0.596], pd = 0.700). Furthermore, we found no side bias, meaning that the location of the flanged male stimuli (left or right on the screen) did not modulate the bias towards flanged males (bleft-right = 0.033 [0.045], 89% CrI [-0.036; 0.104], pd = 0.773). Figure 1. Results of Experiment 1 depicting (A) predicted probability of fixating first on the flanged male stimulus and (B) predicted proportion of time spent fixating on the flanged male stimulus. We report the overall prediction and the predictions for each participant. Grey areas represent the posterior predictions for each iteration of the model, black dots indicate the median posterior prediction, and black lines indicate the 95% credible interval.Tom Roth.indd 165 08-01-2024 10:42