Do dogs really see in just black and white? What about humans vs dog vision at night? In this video, explore and get answers to the world of dogs and questions about their vision. Find out what dog vision looks like. Like most mammals, dogs have only two types of cone photoreceptors, making them dichromats. These cone cells are maximally sensitive between 429 nm and 555 nm. Behavioural studies have shown that the dog's visual world consists of yellows, blues and grays, but they have difficulty differentiating between red and green, making their color vision equivalent to red-green color blindness in humans (deuteranopia). When a human perceives an object as "red," this object appears as "yellow" to the dog, and the human perception of "green" appears as "white," a shade of gray. This white region (the neutral point) occurs around 480 nm, the part of the spectrum that appears blue-green to humans. For dogs, wavelengths longer than the neutral point cannot be distinguished from each other, and all appear yellow.
Dogs use color instead of brightness to differentiate between light or dark blue/yellow. They are less sensitive to differences in gray shades than humans and can also detect brightness with about half the accuracy of humans. The dog's visual system has evolved to aid in hunting. Dogs have been shown to be able to discriminate between humans (e.g., identifying their human guardian) at a range of between 800 and 900 metres (2,600 and 3,000 ft); however, this range decreases to 500-600 metres (1,600-2,000 ft) if the object is stationary. Dogs can detect a change in movement that exists in a single diopter of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movement. A test has estimated poodles' visual acuity to have a Snellen rating of 20/75, a relatively low score compared to humans' vision.
As crepuscular hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum. The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and the overall diameter of the eye. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance is associated with an adaptation toward superior night vision.
The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations. Many long-nosed breeds have a "visual streak"-a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent vision. Some long-muzzled breeds, in particular, the sighthounds, have a field of vision up to 270° (compared to 180° for humans). Short-nosed breeds, on the other hand, have an "area centralis", a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans.
Most breeds have good vision, but some show a genetic predisposition for myopia-such as Rottweilers, with which one out of every two has been found to be myopic. Dogs also have a greater divergence of the eye axis than humans, enabling them to rotate their pupils farther in any direction. The divergence of the eye axis of dogs ranges from 12-25°, depending on the breed. Experimentation has found that dogs can distinguish between complex visual images such as those of a cube or a prism. Dogs also show attraction to static visual images such as the silhouette of a dog on a screen, their own reflections, or videos of dogs; however, their interest declines sharply once they are unable to make social contact with the image.
This video used the following article under Creative Commons - CC BY-ND 4.0 DEED: "Do dogs really see in just black and white?" (theconversation.com/do-dogs-r...) Nancy Dreschel, Associate Teaching Professor of Small Animal Science, Penn State (Published: July 2, 2020); slight stylistic modifications to original text.
16 май 2024
