The 5 senses that people have are also shared with dogs, but to extremely different levels. Some senses are more developed in people than in dogs, and vice-versa.
The ability of a dog to detect motion and light is greater than that of a person. They have a large number of a particular type of cell in their retinas, called rods. Rods are efficient in picking up faint light, enabling and increasing night vision. Incoming light is enhanced via a reflective film (tapetum lucidum) in the dog’s eye. It is tapetum lucidum that makes the eyes of a dog appear bluish-green when light is shined on them at night. However, when it comes to differentiating the fine details of objects, a person’s visual acuity is better than that of a dog. Distinguishing colours is also a problem for dogs, as they don’t have enough retinal cells (cones) for colour definition. Though most people believe so, dogs are not totally colour blind.
Dogs’ eyes have a special feature called the nictitating membrane, also known as the third eyelid. It is whitish-pink in colour and is located in the inside corner of the eye, below the other eyelids. It usually stretches up to shield the eyeball from scratches when moving through underbrush, or as a result of inflammation.
Compared to a person, the dog’s ear canal is a lot deeper and thus better suited to transmit sounds to the ear drum. A dog’s auditory ability is four times stronger than that of the normal person, and can detect higher frequency sounds. Dogs are also able to determine the direction of a sound, making them adept during hunting. However, the presence of a deep ear canal makes them susceptible to ear infections and inflammation, caused by build up of wax, moisture and grease. Things are not made any easier by having floppy or hair inside the ears, which restrict air flow. For this reason, dogs require regular ear cleaning.
Smell and Taste
The sense of smell that a dog possesses is astonishingly powerful. In fact, it is almost a million times more receptive than that of people. They can discover minute odours and differentiate between scents. It is for this reason that they are used to detect drugs and bombs at airports, look for victims at disaster sites (even under water), and track the scent of criminals.
The molecules of a particular odour are absorbed by the moisture that usually internally covers the nose of a dog. Messages are then transmitted to the olfactory centre of its brain, which happens to be 40 times larger in dogs than in people.
There is also an organ at the top of the dog’s mouth that enables it to determine the taste of a particular scent. Just like people, a dog associates tastes and smells, but is able to know more about food from smell rather than taste. The quantity of taste buds that a dog has is around one-sixth that of a normal person, rendering their ability to taste ineffective.