Living with a cat that loves nothing better than to ambush your legs, or attack you when you try to stroke it can be very unpleasant and often extremely painful! Treatment of aggressive behaviour can be very successful; however, it does require understanding of why the cat is motivated to show aggression.
The two main reasons for aggression to develop in cats are because of fear, or because they have learnt an inappropriate way of interacting with their owner. Fear aggression is a defence strategy, which occurs when the cat is feeling threatened. Play behaviour can be termed aggressive when it is directed at an inappropriate target, e.g. human hands and feet.
In order to learn that different situations are ‘normal’ and ‘safe’, cats have to experience them very early in life. Things that are not encountered early on will be more likely to be scary to a cat when it encounters them later in life. Cats that were not well socialised with people as young kittens (between 2 and 8 weeks of age) will be less likely to approach people and may feel threatened by contact with people.
Other cats may become fearful due to a bad experience with people later in life. Individual cats can feel threatened by different ‘levels’ of interaction with people, e.g. one cat might feel threatened by a person approaching, while another enjoys close contact but feels threatened when picked up.
If a cat shows aggression and the person moves away or puts them down, then that aggressive behaviour has been successful. Consequently, every time a person approaches and the cat shows aggression, the aggressive behaviour becomes increasingly established as a successful response to this ‘threat’.