|The Question: My seven year old daughter asked me why our dog will not watch television. I told her that because the TV does not emit smells, he cannot “see” what’s on. Was I correct?
Submitted by: Rich, USA
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The Short Answer: The first thing I have to say is that many dogs will watch television, so maybe you just aren’t turning on Ralphie’s kind of show. A quick search on YouTube will find quite a few dog-watching TV videos. This one has both dogs and cats watching TV. http://www.youtube.com/watch?v=JZVUxuyhIog. You can also find videos of birds, rodents and even fish apparently watching TV.
Of course, it’s hard to know what animals are seeing or how they interpret it. But eye movement tracking studies show that dogs are less interested in a blank video screen than one with a picture; that when shown a complicated scene with a dog in it, they zero in on the dog; that they are more interested in dog faces than human faces on a screen; and that when trained to do so, they will fetch objects shown on a screen. All of that suggests that they can interpret what they are seeing on a video screen as being something like what they see in the real world.
Can Dogs See What They Cannot Smell: Some animals, like Ralphie, don’t ever seem to figure out television, or just can’t be bothered. They’re more interested in the real world around them – or napping – than they are in the flashing box. I don’t think your suggestion that Ralphie doesn’t “see” the TV because the TV doesn’t smell is quite right. The senses of dogs are just as separate as our own and dogs are certainly capable of reacting to things they see visually, but can’t smell or hear. It is definitely true that dogs rely on smell more than we do, and more relevant to the TV issue, it certainly seems that they often find things they smell more interesting than things they see. And if it’s something they can see AND smell, then it really starts to become exciting.
So my guess is that your idea about the lack of smell from TV is not strictly true, in that Ralphie can almost certainly see what’s on your TV. But I’m also willing to bet that you are right in that if TV smelled more like real life, Ralphie would find it much more interesting.
Do Dogs See the Same Thing We Do on TV? Most people know that dogs don’t have the same kind of color vision we do, but dogs don’t see in black and white, as is commonly thought. They have two types of color sensing cells (cones) in their eyes, whereas people have three. As far as we can tell, this means dogs see the world in more muted colors, that are probably like what we see as blue and yellow. They don’t seem to be able to distinguish green from red very well.
Our eyes and the eyes of dogs also have other light-sensing cells called rods. These cells don’t detect color differences, but they are more sensitive to light than color-sensing cone cells. So when the light becomes dim, we get less and less information from the cone cells and we rely more and more on our rod cells. That’s why in dim light, it’s very difficult to distinguish colors.
As primates, our ancestors were probably daytime creatures. With plenty of light, we make use of the extra information that is available in colors. It can tell you, for example, whether a fruit is ripe or not. The sensitive center of our vision is dominated with cones cells so that we can see very sharp color details in daylight. The wolf ancestors of dogs, however, were probably adapted to hunting in low light conditions. Their vision is much more sensitive to low light than ours. The most sensitive central part of their vision is made up of 90% light-sensitive rod cells that don’t distinguish colors very well. In addition, dogs have a tapetum lucidum, a special cell layer behind the retina that reflects light back through the retina, so that the photons that go straight through the retina have a second chance to be detected when they bounce back. Unfortunately, while this increases sensitivity, it blurs the image. (The tapetum lucidum, by the way, is the reason the eyes of dogs and many other animals reflect light in the dark, unlike the eyes of people and other primates, which do not have this feature.)
A dog can see much better than we can in the dark, but we can see more clearly and sharply in good light. Tests of visual acuity in dogs suggest that their vision is the equivalent of about 20/75. This means that something the average person can see clearly at 75 feet (23 meters) would need to be within 20 feet (6 meters) for the average dog to see it clearly. Of course, some dogs see better than others and some breeds are more prone to near-sightedness than others, but the bottom line is that it’s possible that when Ralphie looks at your television, it doesn’t look like High Definition at all.
The other complicating factor is that televisions can flicker. A video screen refreshes many times a second. Once that “refresh rate” is above about 60 times per second, most people can’t detect the flicker and it seems like a steady picture. Tests have shown, however, that until the refresh rate gets to be more like 70 or 80 times per second, dogs can see the flicker. Modern HD TVs refresh at 120 times per second or higher, so they presumably work better for dogs. But older TVs may drive them a little crazy with the flickering.
So, between the lack of smell and the blurry picture and flickering screen, it’s entirely possible that Ralphie sees you watching the TV and wonders, “Why do my people stare at that annoying flashing light?” That certainly seems to be the attitude of my dog, Bella.
Sources: Miller, P E, & Murphy, C J. (1995). Vision in dogs. Journal of the American Veterinary Medical Association, 207(12), 1623-34.
Somppi, S, Tornqvist, H, Hanninen, L, et al. (2012). Dogs do look at images: Eye tracking in canine cognition research. Animal cognition, 15(2), 163-74.[cite]