Hmmm...It depends on what their definition of "personality" is. If it is means traits that people would have if they did similar things then I agree animals have personality in a sense. Many animals of the same type will show different traits even between others of the same species. There is a difference in biological or trained quirks and emotion however. I know a lot of dogs that have become hyper and run around all the time. Being hyper might be considered a "personality trait" by some people. However that is a long ways off from saying the dog feels the emotion of exhilaration or panic like a human does. The same could be said of a cat that plays with it's pray after it catches it. Does the cat actually feel like being sadistic or have hatred for it's pray like a person might? I would say it's biological encoding that makes them do it, not that it feels like it wants to put torment into a mouse.