Page 175 - Demo

Eye-tracking reveals bias to flanges in orang-utans1737shift effects in women because they have failed to find changes in mate attraction across the menstrual cycle (Stern et al., 2021) or a conclusive relationship between reproductive hormone levels and attention towards mate-relevant information such as facial masculinity (Garza & Byrd-Craven, 2023). Nonetheless, investigating the concordance between sexual motivation and attentional biases in orangutans might help further elucidate the link between mate choice-relevant stimuli and visual cognition in non-human primates.In Experiment 2, we presented the orang-utans with multiple unique stimuli of four Bornean orang-utan males. Given that the topic of variation in individual preferences of females has received relatively little attention in the past (Jennions & Petrie, 1997), we explored the individual attentional preferences of the three orang-utan females that participated in our study. While we found some robust differences in attention towards the four males at the individual level, all of these differences concerned pairs of flanged and unflanged males. Thus, we did not observe subtle attentional preferences, such as a preference for one flanged male over another. In general, studies on primate attention have mostly focused on differential attention towards specific stimulus categories, such as emotional versus neutral stimuli (Pritsch et al., 2017), familiar versus unfamiliar conspecifics (Hanazuka et al., 2013; Lewis et al., 2021), same-sex versus other-sex stimuli (Lonsdorf et al., 2019), or presence versus absence of facial characteristics (this study). However, we believe that it would be interesting for future studies to move beyond such classifications and look more into individual preferences. Admittedly, this would be a challenging endeavour that might require larger samples and more diverse stimulus sets. Nevertheless, it is relevant to explore such preferences, as studies in humans have already shown that humans exhibit considerable inter-individual differences in gaze patterns (Rogers et al., 2018) and that individual preferences for salient traits such as attractiveness are predictive of attention (Leder et al., 2016; Roth et al., 2023). One potential approach would be to employ reverse correlation techniques to create classification images per participant, which represent the face that attracts their attention. This technique has been widely applied to study human face perception (Dotsch & Todorov, 2012; Karremans et al., 2011) but has not yet been employed to study great ape cognition. Overall, while we found some individual differences in female attention towards male orang-utans, future research could benefit from a more individualized approach to examining primate attentional preferences.Tom Roth.indd 173 08-01-2024 10:42