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General discussion2139has been successful in elucidating the effect of emotion information on cognition in multiple primate species (King et al., 2012; Kret et al., 2016; Lacreuse et al., 2013; Schino et al., 2020; van Berlo et al., 2023), inconsistencies remain as well, as both chimpanzees (Kret et al., 2018; Wilson & Tomonaga, 2018) and Bornean orang-utans (Laméris et al., 2022) do not seem to show the expected attentional bias towards emotions in the dot-probe task. One important methodological explanation for these inconsistencies is that the dot-probe paradigm relies on reaction times as a measure of attention. However, reaction times are inherently noisy (Morís Fernández & Vadillo, 2020) and may involve trade-offs with accuracy (Draheim et al., 2019). Especially in species with reduced manual dexterity compared to humans, this may obfuscate existing biases. Some of these issues can be resolved by employing non-invasive eye-tracking, as I did in Chapter 7. These methods allow disentangling different attentional processes (Clauss et al., 2022), and, speaking from own experience, seem to yield less noisy data compared to reaction time tasks. Thus, even though the dot-probe paradigm has helped to gain insight into attentional processes of primates, I consider eye-tracking a better alternative, because it yields more reliable and less noisy data, thereby allowing for a more fine-scaled analysis of different attentional processes. It is important to note that eye-tracking is especially suitable for investigating overt attentional processes, because it relies on eye movements. However, attention also operates without eye movements, a process referred to as covert attention. Covert attention refers to a shift in focus, that precedes eye movements (Weierich et al., 2008). Nonetheless, employing eye-tracking in combination with cuing tasks allows one to distinguish between covert and overt attention by investigating whether attentional biases are present in the absence of eye movements (e.g., Petrova et al., 2013), although such study designs might be too complex for non-restraint experiments in primates. Concluding, eye-tracking seems a more suitable method to investigate overt attentional processes in primates, but cannot give insight into covert attention in primates.Practical implicationsIn Chapter 5, I showed that initial attraction during a speed-date predicts fixation duration in an eye-tracking task. This result establishes a link between attentional Tom Roth.indd 213 08-01-2024 10:42