Page 148 - Demo

Chapter 6146Figure 6 – Posterior predictions of the probability of selecting the flanged male stimulus as a function of the vertical position of the dot representing the flanged male on the screen. Negative values indicate that the dot associated with the flanged male stimulus was positioned in the higher portion on the screen, while positive values indicate the lower portion of the screen.DiscussionEven though face perception in primates has been studied extensively, the interplay between facial traits relevant to mate choice and cognition has received relatively little attention, especially in great apes. Therefore, the aim of this study was to investigate whether zoo-housed Bornean orang-utans (Pongo pygmaeus) have cognitive biases for males with fully developed secondary sexual traits (flanged males) or males with more symmetrical faces. Across two experiments, measuring either immediate attention bias or choice bias, we found no evidence of cognitive biases towards facial traits that might be relevant for mate choice. This lack of biases was consistent between all participating individuals. Furthermore, we did not find evidence for either temporal clustering or dispersion in the preference test: orang-utans did not seem to alter their choices based on their response in previous trials. However, we did find evidence of (i) a robust colour bias and (ii) an energy conservation strategy in the preference test. Below, we discuss our results in the context of primate literature and orang-utan ecology, and consider methodological limitations. Contrary to our hypotheses, we found no evidence for immediate attentional biases towards either large flanges or symmetrical faces in the dot-probe Tom Roth.indd 146 08-01-2024 10:41