The Truth About Cats and Dogs: The Psychology of Pet Preferences

It's important to note that these effects were not contingent on gender - men and women alike fell into these rough types based on their animal preferences. Also worth consideration: the study was based on people self-identifying as a dog or cat person, not on what they actually own. So, the cat lady from the Simpsons could identify as "a dog person" and could ostensibly see herself in the description.

Fashion and lifestyle blog Jezebel brought up some "other factors can influence your preference: the animal you were brought up with, and which animal you, um, most closely resemble." 

Jezebel has a great point - and it's also backed up with solid research. Stanley Coren of the University of British Columbia has found that people do tend to have a preference for pets that they resemble, both in terms of appearance and personality. Part of the reason for this is due to familiarity - people tend to harbor more warm and loving feelings for things that are familiar to them. The more that an animal reminds someone of themselves in personality or appearance, the more likely that people will choose that animal as a pet. So, being a "dog person" or a "cat person" might just be the logical outcome of having a "dog personality" or a "cat face!"