How the World looks? The Perception of Animals
Have you ever thought that when you and your pet dog (or cats- I'm not a cat person so I'll just keep them in parenthesis) are spending a lazy weekend on the couch, watching a movie on the television, you both are essentially looking at two different movies?
How your dog sees the movie scene
https://images.app.goo.gl/vXL2y3enjyRFJxg27
Image credits: Klaus Schmitt
If you think that I'm trying to confuse you with some kind of riddle, then you are absolutely wrong! Your pet has a different visual perception than you, in simpler terms it means that all the colours that you are able to see in your surroundings may not be visible to your dog. In fact, it's not just dogs or cats, but nearly every different animal has a unique vision ability and as a result, they see a world that is quite different from what meets our eyes!
Today we make an attempt to see the world through the eyes of 3 peculiar animals known to us, and unveil the science behind it.
1] Dogs
Dogs have a dichromatic vision, which implies that they can see only a part of the visible spectrum, usually two main shades of colours of the spectrum- blue and yellow, unlike us, because we have trichromatic vision and we can thus see the whole visual spectrum.
How you see the movie scene V/S
https://smilegotnessa.files.wordpress.com/2013/02/color-vision-for-a-human-versus-for-a-dog.jpg
The reason behind this is that we have 3 types of cones, while dogs have only 2, as explained in the graph below:
But wait, if you thought that you have a better vision than dogs, here are some interesting facts:
i) Dogs can see 4 times better than us in the dark, which is attributed to the fact that while a human's eye has the central area of its eye devoted to cones and fevoa (which aids visual resolution) the dog's central region of the retina is mainly composed of rod cells that see various shades of grey much better and the rods activate in much lower light conditions.
ii) Dogs have much better motion detection than humans, which helps them to detect the slightest movement of their prey.
iii) Dogs can see flickering light better than humans. While our threshold is said to be around 16 Hz minimum (16 frames per second), flicker fusion rate for dogs is estimated to be as high as 70 to 80 Hz.
2] Birds
In contrast to our trichromatic vision, birds usually have tetrachromatic vision. You can think of birds as having between 2 and 8 times the visual acuity of humans! Although it also depends on the bird species you’re talking about.
https://www.boredpanda.com/human-vs-bird-vision/?media_id=human-vs-bird-vision-5da475ccbf216__700
The above image compares the human spectral field of vision to that of a bird’s. As birds are tetrachromats, they see four colors: UV, blue, green, and red, whereas we are trichromats and can only see three colors: blue, green, red. Bear in mind, that the magenta UV “color” shown here has been chosen to make it visible for us humans, it is a “false color”, as per definition UV light has no color.
But birds like owls have always been thought to have very poor eye sight. It is true that they are almost blind during daytime but they have relatively massive eyes, stuck in a fixed position in their eye sockets, in their skulls. To look around, they have to move their heads, rather than their eyes. That’s why owls have those famously flexible necks that can rotate their heads in almost 360 degrees.
The retina of a large owl can be larger than the retina in your eye. And owl retinas are packed with rod cells. Recollect that cone cells are adapted for color vision whereas rod cells are best for nocturnal vision. Well, owls have almost all rods in their retinas. So, they have superb night vision.
Another major difference is while our binocular vision confers better perception of depth, the monocular vision of birds enables them with a wider field of view.
3] Cows
A few decades ago, it was assumed that cows are colourblind, but research has proved that they can distinguish colors and can distinguish on a gray background all colors except blue. In fact, they can distinguish colors with longer wavelengths (like red, orange and yellow, however they'll see them in shades of brown because they do not have full colour vision) much better than colors with shorter wavelengths (such as green, blue, purple and gray) and this offers a survival mechanism to allow them to see if a member of the herd was attacked and blood was drawn from it, so that they can escape.
https://images.app.goo.gl/NR7wiDYnoWL5kqHr8
A major boon for cows is that they have panoramic vision which allows them to see in all directions without moving their heads.
However, cows have slit-shaped pupils and weak eye muscles as a result of which their power of accomodation is poor. As a consequence, they also have poor depth perception because they have limited vertical vision of about 60 degrees, compared with around 140 degrees for humans. That's the reason why you'll see cows avoiding shadows on the path as they cannot tell if a shadow is a hole or ditch and try to figure out by bending their head close to the shadow.
References
Coren, Stanley. “Can Dogs See Colors?” Psychology Today (2008): n. pag. Psychology Today. Canine Corner, 20 Oct. 2008. Web. 16 Feb. 2013.
https://www.psychologytoday.com/us/blog/canine-corner/200810/can-dogs-see-colors?amp
https://www.boredpanda.com/human-vs-bird-vision/
https://animals.mom.com/cows-poor-eyesight-4622.html
