Page 157 - Demo

Eye-tracking reveals bias to flanges in orang-utans1557IntroductionMate selection is a crucial process for sexually reproducing animals. The choice of a mate fundamentally defines an individual’s biological fitness: picking a good partner can ensure that genes are well represented in the following generation, whereas picking a bad partner can cause genes to disappear from the population (Buss & Schmitt, 2019). Numerous species have evolved certain preferences that direct them when selecting a partner as a result of this significant motivation to do so (Rosenthal, 2017). Thus, these motivations influence cognition. In humans, for instance, various cognitive processes such as visual attention seem to be affected by sexual selection, and these processes can aid in identifying suitable mates or competitors (Maner & Ackerman, 2015). However, relatively little is known about the cognitive underpinnings of mate selection in other animals. In the current study, we investigated whether Bornean orang-utans, a species characterised by extreme sexual dimorphism (Utami Atmoko et al., 2008), showed an attentional bias towards fully developed flanged males.The interplay between sexual selection and visual attention has been extensively studied in humans. Many studies have found that heterosexual women and men have an attentional bias towards attractive members of the opposite sex (Leder et al., 2016; Mitrovic et al., 2018; Roth et al., 2022, 2023). Similarly, humans also show vigilance toward attractive same-sex individuals (Maner et al., 2009). Importantly, such attentional biases have been identified for both immediate (e.g., Roth et al., 2022) and voluntary attention (e.g., Leder et al., 2016; Roth et al., 2023). Immediate attention constitutes automatic orienting towards relevant stimuli such as fear-inducing animals (Shibasaki & Kawai, 2009) or faces (Kawai et al., 2016). The typical measurement used to assess immediate attention is the time it takes for a participant to attend to any given stimulus after its onset. Voluntary attention reflects the deliberate and self-directed allocation of attentional resources to stimuli (Souto & Kerzel, 2021) and is typically measured as a function of the total time that participants spend looking at any given stimulus (Roth et al., 2023). In humans, attentional biases towards attractive faces also seem to extend to sexual dimorphism: both men and women seem to have a visual bias for more masculine male faces (Garza & Byrd-Craven, 2023; Yang et al., 2015). Interestingly, this is not only the case in humans: rhesus macaque (Macaca mulatta) females look significantly longer at the more masculine faces of conspecifics (Rosenfield et al., 2019). This implies that attentional biases towards such sexually selected traits can also be found in non-human primates.Tom Roth.indd 155 08-01-2024 10:41