Abstract
Eye movement of a species reflects the visual behavior strategy that it has adapted to during its evolution. What are eye movements of domestic dogs (Canis lupus familiaris) like? Investigations of dog eye movements per se have not been done, despite the increasing number of visuo-cognitive studies in dogs using eye-tracking systems. To fill this gap, we have recorded dog eye movements using a video-based eye-tracking system, and compared the dog data to that of humans. We found dog saccades follow the systematic relationships between saccade metrics previously shown in humans and other animal species. Yet, the details of the relationships, and the quantities of each metric of dog saccades and fixations differed from those of humans. Overall, dog saccades were slower and fixations were longer than those of humans. We hope our findings contribute to existing comparative analyses of eye movement across animal species, and also to improvement of algorithms used for classifying eye movement data of dogs.
Highlights
Visuo-cognitive abilities of domestic dogs have been an important topic for many researchers (Bensky, Gosling, & Sinn, 2013)
We first examined whether the saccades of dogs and humans show the systematic relationships between saccadic metrics previously reported in the studies of humans and other animal species
Saccades of both species showed the typical pattern of the main sequence and Carpenter’s relationship, where the peak velocity (X2(1) = 211.14, P < 0.0001) and the duration (X2(1) = 71.60, P < 0.0001) of both species saccades significantly increased with amplitude, respectively
Summary
Visuo-cognitive abilities of domestic dogs have been an important topic for many researchers (Bensky, Gosling, & Sinn, 2013). Studies of saccade and fixation characteristics in awake stimuli-viewing dogs are non-existent This void contrasts with the vast amount of literature on eye movement characteristics of other animal species such as nonhuman primates, rodents, birds, reptiles, and felines that appear in reviews (Hardcastle & Krapp, 2016; Land, 2015, 2018; Sparks, 2002). Evinger & Fuchs (1978, Fig.3) Collewijn (1970, Fig.5) Easter Jr (1975, Fig.5) Chen et al (2016, Tab.1) The former studies have called the need for more interdisciplinary comparative analyses involving diverse animal species to explore saccade mechanisms and its evolution (Hardcastle & Krapp, 2016). Information on dog eye movement and their data characteristics is required, especially that based on the data collected in free viewing tasks, to evaluate and improve current default algorithms and threshold settings used in dog eye tracking. We discussed dog eye movement characteristics in relation to their morphology and evolutionary history compared to those of humans and other animals
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