Page 217 - Demo

General discussion2159section above), there are some other caveats that should be addressed before such an approach can be considered useful.First, while I found a robust bias towards flanged male stimuli in the eyetracking experiments described in Chapter 7, I did not find clear indications of subtle individual attentional preferences in Experiment 2, where individuals were presented with multiple stimuli of four different males. While I found a few robust biases towards one specific flanged male compared to the unflanged males, none of the females seemed to attend more to one specific flanged male compared to another flanged male. This is not to say that it would be impossible to identify such preferences via eye-tracking. However, it would require larger samples than studies that investigate attentional biases towards a specific stimulus category. This may not be feasible in zoos, because it would be a time-consuming endeavour. Instead, it might be more promising to develop methods that require little time investment and are intrinsically rewarding for participants. For example, one could explore designs in which individuals self-expose to stimuli or can trigger video calls with or video fragments of different conspecifics. For example, a recent study in parrots (order Psittaciformes) employed a free-choice paradigm where individuals could trigger video calls with other parrots and interact with them (Kleinberger et al., 2023). Given that such methods rely on intrinsic motivation, they may be better suited to investigate individual preferences compared to extrinsically rewarded tasks. Second, it will be important to establish a link between performance or biases in cognitive tasks and later behaviour. For example, if we assume that we can reliably measure a cognitive preference towards one specific individual over another, would this also translate into more affiliation or even a higher probability of successful reproduction with this individual? This thesis suggests that such a link may exist in humans, at least when considering the eye-tracking results. However, a similar link has, to my knowledge, not yet been established in non-human primates.A final practical implication from this thesis concerns the ovulatory shift in female preferences. In Chapter 8, I reported two cases of Bornean orang-utan females who were especially sensitive to flanged male signals (auditory or visual) in their peri-ovulatory period. This corroborates findings from wild Bornean orangutans (Knott et al., 2009), and may also be relevant for the future development of test paradigms to identify mate preferences. As I argued in the “Theoretical implications”-section, it could be the case that the attraction-filter is especially Tom Roth.indd 215 08-01-2024 10:42