DOGS have the same five senses as man. The sense of sight, sound, touch, smell and taste.
Dogs seem to be always sniffing the ground, the air, trees, objects and humans. They do this not just out of curiosity - it is how they process information about the world around them.
Their nasal passages are designed to receive and trap odours. The scent nerves are large and numerous. Just inside the roof of the mouth is an organ called the Jacobson's organ or the nasal-vomero organ, which helps the dog process the different smells.
The scenting ability of humans is not so highly developed. We have an estimated 5 million olfactory cells used for smelling in a very small area at the back of the nose. By comparison dogs have scent cells spread all over a large area and have an estimated 125-220 million scent cells depending on the size of the dog.
They can use each nostril independently and are good at distinguishing one odour from another and remembering it.
The part of the brain that receives messages from the nerves of the nose is highly developed and can store up scent information like a computer. Sometimes my dog will fail to recognise me if I am dressed differently until I get within his range, for him to identify my scent. Then he wags his tail welcomingly.
Puppies find their mother by using their sense of smell immediately after birth. The Dam will lick them to place her smell on the puppies and then lick her teats to help the puppies find their way back to her. Without their sense of smell at birth the puppies would not be able to find their mother. Without the sense of smell the first imprinting could not even begin. So this is of course the most important sense to a dog.
To the human this is the second most important sense of all next to touch as without it we could not find our way around by using any other sense. Humans are very visual and we are lost without it. We see well and will go to the expense of buying glasses when our vision begins to fail.
We won't even eat something we don't like the look of, no matter how nice it may smell. Dogs on the other hand smell first and then eat it, what it looks like is not important to the dog. However at night time the dog's sight is superior to ours. The dog's eyes are sensitive to light and movement. They are able to dilate the pupils to take in any light around them in order to see better at night. They cannot see in absolute dark but are good at seeing when there is little light. The dog has many receptor cells or rods and a reflective layer called the tapetum lucidum, which reflects light back to the receptor cells giving the appearance of the eyes glowing in the dark.
Dogs have poor binocular vision so they see a wider view at longer distance rather than close up. This is why they sometimes see something at a distance before humans do, such as a cat in the distance up a tree. This sight is great for hunting and some breeds are used for their ability to sight and hunt or point at long distance such as hounds and pointers.
Another interesting fact is that dogs do see colour. Once people thought that dogs could only see black and white and shades of grey. Experimental evidence shows that dogs can see various distorted shades of green and blue.
The dog's hearing is very similar to human hearing and probably about equally important. He can hear low notes just as we do but his hearing is more acute. He can hear much higher notes and sounds than humans. He can also move his ears around to scan the environment for different sounds. They can hear sound from a greater distance than humans as he moves his ears around to catch the sound waves and locate where the sound is coming from more accurately.
In the wild the dog's ability to hear high pitch sounds helps him to hear, track and locate the sounds of small prey such as mice and rabbits that make high-pitched squeaks.
The dogs' tongues are similar to our own. They can detect sweet, sour, bitter and salty just the same way we do. The sense of taste is functioning right from birth when the puppies will be led to the warm texture and sweetness of the milk by their mother's smell and touch.
Food is usually bolted down very quickly by dogs with hardly any chewing or time to taste it. Taste does not seem to be as important as the smell of the food, then the texture and then last of all the taste. I have noticed with my own dogs and tests with dogs have proven that dogs do prefer to eat something smelly and the stronger the smell the better.
Humans have a more refined sense of taste with around 900 taste buds on the tongue, while dogs are thought to have around 1706 taste buds on their tongue.
The sense of touch is very important to the dog as it is with humans. I feel this is the most important sense of all to a dog and to humans alike. Without it a puppy could not locate its mother at birth and it could not develop into a normal balanced dog, it would become fearful and with drawn.
At birth the puppies have receptors in their faces so they can locate their mother if they become separated before their eyes are open. The need for touch continues throughout the dog's life and is a very important part of training and reward. For humans touch is also important for the growth and development of a well-balanced child.
Without touch a child would grow without a feeling of being loved, which would have a devastating effect on its adult life. Dogs have sensory nerves all over their bodies, just as humans do. Dogs thrive on being touched and stroked and there are mutual benefits in owning a dog.
Stroking a dog is known to be therapeutic, reducing blood pressure, calming nerves and causing people to live longer. This is why it is beneficial for trained dogs to be taken in to residential homes, hospitals and schools so that those who have no access to animals can stroke them, benefiting both dogs and humans.