Cats come in many breedsthough not with the same degree of diversity as dogs. The recognized number of cat breeds varies depending on the organization. The Cat Fanciers' Association recognizes 45 pedigreed breeds as well as the "companion cat," also known as "most regular cats," while the International Cat Association recognizes 73 breeds.

These breeds include relatively well-known varietieslike the slender Siamese cat and the fluffy Persianas well as the leopard-spotted Bengalthe short-tailed American bobtail and the hairless Sphynx.

While dogs have been bred over centuries to carry out different tasksleading to a variety of sizes and shapes of dogdomestic cats have only two jobs: controlling pests and being pets. This means that most pedigreed cats are bred for traits such as color and fur length rather thansaya waterproof coat for swimming or a strong herding instinct for guarding sheep. Most cat breeds date to less than 100 years ago — although older breedslike the Egyptian Mau or Persiandate back further.

Cats are intelligentand the widely held belief that dogs are smarter than cats may not be supported by science. Felines display object permanence — or the ability to realize that something still exists when it's out of sight — which is an ability humans only develop when they are around 8 months old. Object permanence is an important skill to have when you're a hunter operating at nightlistening for the telltale patter of tiny mice feet. Cats also recognize their owners' voices.

But cats don't always make their smarts easy to measure. "They're a nightmare to work with in the lab," said Julia Meyers-Manora psychologist at Ripon College in Wisconsin who studies animal cognition.

Compared with other animalssuch as rats and dogsfew studies have been done on cat intelligenceMeyers-Manor told Live Science. Cats hate strangers and unfamiliar placeslike labsshe said. They typically bury their faces in their owners' arms and refuse to cooperate with the task at hand.

Cats might not be the most socially savvybut there is evidence that they form bonds with their humans. Cats can develop separation anxietyoften displayed by peeing or pooping somewhere they shouldn'tand studies also suggest that cats rely on emotional cues from their owners when responding to new situations. Cats also seem to recognize the emotions of both humans and other cats.

Cats have excellent nighttime vision. Their eyes are equipped with many rodsor special cells in the retina that are good at capturing dim light. This enables cats to see six to eight times better in the dark than humans can. A reflective layer in the eye also helps collect extra light at night. This layer is what makes cats' eyes shine green if a flashlight or headlight catches their eye in the dark.

Research suggests that cats can see ultraviolet lightwhich is blue light outside the range that humans can see. Cats likely don't see color as well as humansthough. They have two types of cells in their eyes that can detect short- and long-wavelength lightwhile humans have three. Their world probably looks more desaturatedor less colorfuland they also can't see long distances as well as humans. Howevercats have a broader field of view than humans do: 200 degrees compared with 180 degrees for people.

Cats aren't particularly strong smellersbut their sense of hearing is very sensitive. Cats can hear frequencies between 55 hertz and 78 kilohertz. For comparisonthe deepest sound a human can hear is 20 hertzand the most piercing high sound is around 20 kilohertz.

Cats still work to control rats and mice around farmsnurseries and warehouses. But most of the timea cat's job is to provide companionship for people.

Science suggests they do their job well. One study found that spending time with a cat reduced heart rate and blood pressure in both owners and volunteers who didn't own cats. Another study found that cats reduced their owners' negative moods. These effects may be tied to changes in brain activity. One study found that playing withpettingtraining and feeding cats all activated a region of the brain called the prefrontal cortex that is linked to empathy and nonverbal communication.

The scientists said that cats' independence seemed to be key to making the cat-human relationship work. Getting a normally uncooperative cat to cooperate with play or training provided a big mood joltthe researchers found. It turns out that for catsplaying hard to get pays off.