Page 132 - Demo

Chapter 6130Orang-utans are a suitable species to study cognitive biases associated with sexual selection. Unique among mammals, orang-utans are characterised by male bimaturism: while some adult males quickly develop secondary sexual characteristics, such as a throat sac, large body size, and conspicuous flanged on the side of the face, other males experience developmental arrest of these characteristics (Kunz et al., 2022). These so-called unflanged males are sexually mature and can successfully reproduce, although females prefer to mate with fully developed flanged males when they are fertile (Knott et al., 2009). Possibly, female preference for flanged males reflects selection for good genes: the transition from unflanged to flanged male is energetically costly, meaning that males of higher genetic quality would be more likely to develop into flanged males (Knott et al., 2009). Furthermore, fierce male-male competition has been described between flanged males, suggesting that flanged males are also at serious risk of being injured during fights (Knott & Kahlenberg, 2011). Thus, by mating with flanged males, orang-utan females might ensure that their offspring has higher genetic quality. Consequently, it could be beneficial to have cognitive biases to flanged males. Another trait that is often mentioned with regard to mate choice is facial symmetry, which might reflect the ability to withstand environmental stress during development (Valen, 1962). While clear associations between health and facial symmetry have not been established in humans yet (Pound et al., 2014), previous work on chimpanzees (Pan troglodytes: Sefcek & King, 2007) and rhesus macaques (Little et al., 2012) has found that more asymmetrical individuals were also less healthy. In addition, macaques prefer to look at symmetrical faces of conspecifics (Waitt & Little, 2006), which shows that this facial characteristic might modulate attentional processes. Thus, individuals might have cognitive biases for symmetrical conspecifics, because selecting a mate with a symmetrical face could potentially result in more genetically fit offspring.In this study, we employ two paradigms to investigate immediate attentional bias towards flanged faces and symmetrical faces, and choice bias for flanged faces. In the dot-probe task (MacLeod et al., 1986; van Rooijen et al., 2017), two different stimuli are simultaneously displayed, each one on a different side of the screen. After a set amount of time, both pictures disappear, and a dot appears on the location of one of the pictures. If the dot appears behind the stimulus that the participant was attending to, the participant can quickly indicate the location of the dot by clicking it. However, if the dot appears behind the stimulus that was not Tom Roth.indd 130 08-01-2024 10:41