The way dogs perceive the world is different than the way we do, but that doesn’t stop them from communicating with us to understand their needs. Besides barking, dogs can connect with us through the way they see the world.
There’s an importance in understanding dog visual processing, especially in training or even daily life. One way we can understand them is through their vision in dim light. Dogs are more scoptic than humans, being able to easily function in dim light. Us humans take time to adjust to dim light and, even then, struggle at times to see. The retinas of dogs are made mostly of rod photoreceptor cells (responsible for color vision) which are extremely helpful in allowing them to function in less intense light conditions.
The reflective tapetum lucidum tissue is another attribute in dogs’ eyes that dictates their sensitivity to dim light environments. This biological reflector system gives light-sensitive retinal cells a second opportunity for photon-photoreceptor stimulation by reflecting light back through the retina again. The enhancement of visual sensitivity in dim light conditions is due to the reflection, however, it also lowers the ability of the dog’s eye to observe details of what is being seen. Increased scattering of light in the eye is to blame for this. This may explain why in the dimmest light, although Coco can see better than I can, she barks like crazy at my brother when he is walking toward us. She can see a figure but can’t make out exactly who it is because she can’t see the details due to the scattering light in her eyes. The size of the tapetal area depends on the breed and body size of the dog but even within breeds, there is variation. Not all dogs from the same breed are identical. Coco is our biggest dog yet somehow she sees worse than my other three.
Visual acuity (clarity of vision) is reliant on optical and neural mechanisms (eye structure, the health of the eye, the brain’s interpretation). Any damage or change to any of these areas can cause trouble with intaking visual information. It’s difficult to measure dogs’ visual acuity, but it is frequently considered to be worse than humans. So while Coco can see in dim light, this does not mean that she can visually take in all of the information in front of her, causing her to bark and retreat.
Not only does the visual matter, but the physical as well. The immense diversity seen in dog facial morphology causes different visual processing capacities between dog breeds. My dog Coco, her face is very droopy and full of skin. Because of this difference in facial structure from her brothers and sisters, her skin will start to pull at the bottoms of her eyelids and her vision can be affected (visual acuity). This can affect how she sees and processes things she encounters in daily life and cognitive tasks. Pair bad visual acuity and damage to the reflective tapetum lucidum tissue, this makes information processing very hard for your dog since they rely on visuals. To help prevent this, ensure your dog is obtaining all their necessary vitamins, nutrients, and antioxidants.
While little is known about how dogs specifically visually perceive their external environment, more research in areas of vision in domestic dogs (i.e., sensitivity to light, visual perspective, visual acuity, form perception, and color vision) will bring us closer to how these abilities can affect performance in cognition tasks in your pup.
Byosiere, SE., Chouinard, P.A., Howell, T.J. et al. What do dogs (Canis familiaris) see? A review of vision in dogs and implications for cognition research. Psychon Bull Rev 25, 1798–1813 (2018). https://doi.org/10.3758/s13423-017-1404-7
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