SENSES
Each being perceives its surroundings differently. Sensory impressions are processed and reactions follow.
In the following you will find a few hints to get a better feeling for how our little friends perceive their world.
Hearing
The human hearing covers a frequency range from about 20 Hertz to about 20.000 Hertz. Most pleasant for us are sounds between 500 and 4.000 Hertz, within which one can find speech and music. Similar to dogs we can not perceive anything with a sound pressure level under 0 Decibel.
The frequency range for dogs goes from 15 to 50.000 Hertz.
To hear something, cats need just a fourth of the sound pressure we humans do and a sound pressure level of just -10 decibel. Their hearing covers a frequency range of approximately 55 Hertz to 70.000-79.000 Hertz which gives them an advantage over humans and dogs. It should not come as a surprise that cats at least twitch if not run when a human is yelling at them or at the sound of a vacuum cleaner because such sounds or fireworks simply cause pain to the animal.
Vision
What we perceive as light are electro-magnetic waves in a range from 380 nm (nanometers) to 780 nm. Everything within this range defines our ability to see. We have 120 million rod cells per eye which are sensitive to light and mainly impact our ability to see in dark surroundings. In addition we have about 6 million cone cells of 3 different kind. S (short) for a range from 400-500 nm (maximum at about 420 nm for violet blue) for blue colors, M (medium) for a range from 450-630 nm (maximum at about 530 nm for cyan green) for green colors and L (long) for a range from 500-700 nm (maximum at about 560 nm for greenish yellow) for red colors. This makes humans trichromates due to the ability of perceiving these three ranges of wavelengths and combine them. The human lens has an optical power of about 19 diopters and can accommodate up to 13 diopters.
Dogs and cats are dichromates without the m-cones which is the equivalent to a red-green-color-blindness. In dogs one type of cones is sensitive to yellow colors and the other type is sensitive to blue violet.
Things that are green to us humans appear colorless for dogs and red appears rather yellow to them. The optical power in dogs is about 41.5 diopters and in cats it is above 50 diopters. Since the lens of a dog can only accommodate 2-4 diopters it is not possible to see objects closer than 30-50 cm sharply. Compared to humans, dogs have a heavily decreased depth perception, color perception and visual acuity but better perception when it comes to gray shades (rod cells) and movements.
The eyes of cats are most sensitive to a wavelength of about 555 nm, what would be green and at 450 nm resembling blue violet. Compared to humans a cat only need a sixth of light to see. Cats do exceedingly well in estimating distances. When it comes to vertical movements, a bouncing ball for example, cats will always miss the first hit. This effect might be related to the form of their pupils. While the ratio of rod cells to cone cells in humans is about 20:1, it is about 63:1 in cats, which also indicates a much better ability to perceive movements. Just like dogs they are missing m cones and red perception with red colors being perceived as yellow. Other than dogs, cats seem to perceive their world dominantly in green and blue colors and apparently preferring blue shades.
Other than humans, cats and dogs have a tapetum lucidum, which reflects light, at the back of their eyes, causing the light hitting their optical cells a second time. This also causes the glowing eyes when light hits them in the right angle.
The lenses of cat can accommodate 9-10 diopters. It is assumed that this heavily declines with age and possibly ceases entirely at some point. When hunting or playing, cats close their eyes when an object comes past a critical distance to protect their eyes. Then, their whiskers take over with the sense of feeling.
Feeling
Cats feel pain just as we do. Their tactile sense is highly developed and distributed all over their body. Especially the vibrissae, like whiskers are called, are connected to a vast network of nerve endings. This allows cats to measure the width of an opening and to determine if it is wide enough to pass through. When a cat’s eyes are closed (see the text about vision), muscles allow a cat to move the whiskers. This allows the sense of feeling to take over further coordination of movements, to protect their eyes.
Cats can lose their vibrissae which then will grow back. To pull them out forcefully, to cut or burn them will cause pain and resembles a temporary handicap for the cat.
The tactile sense in their front paws is of great importance for it is so sensitive that cats can perceive vibrations in the ground caused by their prey.
Smell
In dogs, smell is the strongest sense. While humans have about 10 million olfactory cells, dogs have about 200 million cells. Cats have about 60 million olfactory cells. It is quite obvious that smell has a totally different significance for each of the three species. Unknown odors can irritate while known odors can provide the feeling of safety. This is why especially uncastrated cats tend to mark the unknown with their own smell and what would be better suited to do so than urine.
Even with far less accuracy humans are capable of smelling certain emotions in their peers, like fear. Similar to dogs, cats can perceive moods on a far wider scope, including the degree of aggressiveness or tension in individuals of their own and other species, which includes their owner.
For cats, smell has a substantial function. They use it to mark territory and possession, to mark objects as harmless, to assess health, maturity, hormonal status and dominance. This allows a male cat to sense that a cat will be in heat soon and start to mate even before the owner becomes aware of the cat’s condition.
Taste
We humans have about 9.000 taste buds. Dogs have about 1.700. However, cats have only about 500. This could be a reason why cats do not have the need to vary the taste of their food.
Above that, cats can not taste sweet which is just another reason for not feeding them cookies meant for humans.
On the other hand, taste and smell are heavily entwined in cats. This can cause a loss of appetite when the sense of smell is impaired.