It's called anthropomorphism - attributing human-like emotions and characteristics to animals and objects. We tend to do that naturally. It's easy to explain our cat's every behavior as if they were a person (albeit a furry one!)
Originally, the scientific opinion was that animals don't have emotions, feel love or shame or jealousy. It was also once believed that animals don't have cognitive thoughts, only instinctual or learned reactions to events in their lives, living strictly in the moment (which can be healthy for humans, actually!)
It's now understood that's not the case. Research has proved what us pet owners have known for a long time, that pets can choose how to react, make decisions and definitely feel emotions based on how we treat them, etc... It's also widely accepted that different animals have different personalities, just like humans. Some are more sensitive, timid, and some are naturally dominant, prone to jealousy, possessive. More than learned behaviors, studies show that this is innate. Shelter animals will build a culture, a shared set of rules and expectations, especially when dealing with new arrivals. Can you imaging a chaotic environment of cats acting purely instinctual?
Communication displays a cat's intention, wants and feelings. Cat owners notice that much of the meowing throughout the day is meant solely for them, even in multi-cat households. Most of cats interactions between themselves is non-verbal - hissing and screaming at their mates being the exception! Generally meows are learned skills to tell us what they want, and rewarded by us providing the response, whether it's food, attention or distress. And astute cat parents learn to distinguish meaning between the various meows, coos and growls - they all express our cat's thought and desires. The use of nonverbal postures and gesturing are also important clues to what cats are thinking and wanting of us. Many cats will tap us with their paw to wake us up, continue a petting session and get our attention. Ignoring us when we return from a long absence sends us a strong message of their disapproval. Conversely, greeting us at the the door or bringing us a favorite toy tells us they are ready for attention. Jealousy is displayed by some cats if you are paying too much attention to a housemate. Some may argue that these are all learned responses, but choosing when and how to interact with us suggests otherwise.
So be a good listener and pay attention you your cats actions. It can improve your relationship just like with us humans!
Source: Catnip Journal from Tufts University.