This involves aggression by a cat towards a person or another cat as a result of the inability of the attacker to get at another object of their aggression. A perfect example of this is the cat at the patio door watching a stray cat. The indoor cat is obviously worked up and wants desperately to get at the intruder but can't. Frustration sets. At this moment the cat, who is totally fixated, becomes surprised by the sudden intrusion of the owner or house mate. The flood of aggression meant for the stray is redirected towards this readily available outlet. The attack can be very vicious and the association can last many weeks or months after the original episode.
Treatment is similar to what was described for fear based aggression. That is, use a pleasurable activity (such as feeding) and gradually associate it with the object of the aggression. If it is the pet owner, have he/she gradually decrease the distance between themselves and the cat (while eating) over a period of several days or weeks. You must back off if at any time the cat shows interest or focus on you while it is eating. It may also be critical to prevent the cat from having continued visual access to any possible inciting cause of aggression. For example, keep shades or blinds closed over windows and doors looking out over the yard where strays may roam.