Functional performance of the visual system in dogs and humans: A comparative perspective

Abstract

Vision in dogs is generally considered poor compared with humans, and recent reports have reviewed some of the physiological principles underpinning dog vision, but a systematic comparison of the physiological and neurobiological features of vision in dogs compared with humans appears to be lacking. This means there is a risk of an anthropocentric perspective of the topic rather than an understanding grounded in a wider biological context. It is also important to appreciate that deficits in one aspect may be compensated for in other parts of the visual system, so generalizing about performance on the basis of a single feature within the visual system might be misleading. This review provides an overview of the visual perceptual abilities of dogs versus humans, grounded in the visual system's physical structures (see supplementary information) for detecting different visual features of the environment through to its initial processing prior to its cognitive evaluation. Differences and variations that exist between dogs and humans and why these might occur are considered, by reference to their natural history (ecological factors affecting their evolution) and differences in morphology (including differences in height, which will affect viewpoint and the visual information available to individuals in the same location). The implications of differences and applications for everyday handling and training of the dogs are discussed throughout.

Visual perception of emotion cues in dogs: a critical review of methodologies

“…The advent of mobile eye-tracking technology (Pelgrim et al 2022 ; Williams et al 2011 ) can extend this work to more ecologically valid settings with real rather than recorded stimuli. While most modern eye-trackers (i.e., based on detecting near-infrared pupil and cornea reflections) have been specifically developed for the human eye, its use with dogs has been remarkably successful, probably due to the similarity between the human and dog pupil and cornea-generated reflections (Barber et al 2020 ; Somppi et al 2012 ). However, dogs do present some differences in their visual system, such as a horizontally wider fovea (Beltran et al 2014 ) and different eye movements (Park et al 2019 ), but it is still unclear if or how these differences may impact visual perception of emotion cues.…”

“…Importantly, in this review we focus exclusively on what is known so far on how dogs are able to extract visual information from their environment (social and non-social) through their specialised visual system (e.g., Barber et al 2020 ; Byosiere et al 2018 ), and perceive emotion cues intra- and inter-specifically. Therefore, this review does not aim at (1) discussing theories of emotions, as this necessarily would include a much more extensive and broad work on experience of emotion as internal states, production of emotion and/or social cues, intentionality, flexibility, control over displays, etc.…”

“…Despite being a species with a tremendous sense of smell, dogs seem to have a well-developed visual system (Barber et al 2020 ; Byosiere et al 2018 ) and a remarkable ability to visually read humans’ communication, emotions, and intentions (Arden et al 2016 ; Huber 2016 ; Lea and Osthaus 2018 ; Reid 2009 ). The recent wealth of studies on the dog (Fig.…”

“…Functional anatomical differences in sensory abilities between types of dog (e.g., see Barber et al 2020 for a comprehensive review of the visual system of dogs relative to humans and its implications) mean that the social environment might be perceived very differently, regardless of any central capacities; i.e., the brain may be receiving very different stimuli which may affect the subsequent processing and behavioural responses. In addition, dogs live in a variety of human environments (companion/urban vs free-ranging/village dogs), which seems to impact, for example, sociability (Bhattacharjee et al 2021 ) but not some perceptual abilities (Bhattacharjee et al 2020 ), although companion dogs have been much more studied than free-ranging dogs.…”

“…Several reviews have been published recently on dog cognition (Arden et al 2016 ; Bensky et al 2013 ; Kubinyi et al 2007 ; Lea and Osthaus 2018 ; Miklósi and Kubinyi 2016 ; Wynne 2016 ), visual abilities (Barber et al 2020 ; Byosiere et al 2018 ; Miller and Murphy 1995 ), and dog–human communication (Siniscalchi et al 2018a , b ), including attention to pointing gestures (Kaminski and Nitzschner 2013 ) and faces (Huber 2016 ). Another review (Kujala 2017 ), followed by a thread of invited commentaries, explored the questions of if and how dogs may experience emotion, but no review has so far focused on the issue of perception of emotion cues, and more importantly on the methodologies used to study this topic.…”