Scientists believe in an evolutionary reason behind cuteness. Cute babies are healthy babies and cute babies get more attention from mom. Let's say someone has a set of fraternal twins; whoever has the most symmetrical face, the biggest eyes, and the nicest smile is going to get more attention. Same with animals. Endangered species that are considered cute have a better chance of surviving than more homely species simply because more people will care (Leonard 2007).
In order to understand why cats are so cute, it's important to explain what makes a baby anything so appealing in the first place.
In terms of evolution, there are certain subtle characteristics about a person that indicate just how healthy it is. It's not that there's some checklist or anything, it's simply that the bigger a human baby's eyes or the smaller it's mouth, the more healthy it is (healthy meaning fewer genetic mutations). Symmetry is also a big factor; it plays a role in not just how we react to babies, but how we find mates attractive, as well.
Large and symmetrical heads, big eyes, and a small mouth and nose make babies very appealing to us. These traits also apply to cats - and to the extreme. Proportionate to size their bodies, cats have the biggest eyes of any land mammal. Include soft fur and you excessive cuteness stuffed into a small, purry package. The cuter something is, the more we want it in our homes and on our laps.
And you know what? They know it's our weakness and they use it against us. A kitten could go into a store and demand that you put all the tuna into the duffel bag and nobody gets hurt and you'd be all like "Okie-dokie, but only if you let me rub your little tummy-wummy first!"
Cats don't just manipulate us in appearance, though. Oh, no - cats have learned to work us into a puddle of obedient mush with meowing and purring. A study by behavioral ecologist Karen McComb found that, as with babies, humans can distinguish between the different kinds of purrs from a cat. We know the difference between a hungry/whining (pleading) purr and one of content (Peeples 2009). To persuade us to fulfill their desires, cats can also employ a high-frequency meow that is incredibly similar to the cry of a human baby.
Have you fallen victim to feline adorability?