Ken spent some time discussing aggression in animals, which he defines as “any unwanted agonistic behavior.” There is a bit of a grey area here, I think; while most people would not consider a cat catching and killing a mouse to be aggressive, to the mouse, it most definitely is. Still, there are some general rules about aggression that seem to hold up regardless of who is discussing it. Where applicable, I have cited the researcher (and year of their published work) whom Ken credited for the rule.
First, most (if not all) animals have some degree of aggression in their repertoire (Lorenz). It’s just normal for animals to be aggressive in order to protect themselves (for example, if they are ill) or their young. Aggression may also be used to determine social hierarchies or who gets access to food or mates. However, Ken was quick to tell us that this does not mean that we shouldn’t take aggression seriously, nor that we shouldn’t try to modify it.
Animals who have the opportunity to aggress will do so more often (Johnson, 1972). Ken told us that most zoo keepers would never even consider engaging in free-contact with lions (no barriers between them) because lions who have the opportunity to be aggressive often are.
An animal who has been food deprived will aggress more readily than an animal who has adequate provisions (Staddon, 1977). This is part of the reason that Ken is so adamant that all animals under his care gets its full rations regardless of whether or not they perform well in training.
The use of punishment or aversive control will cause aggression (Kazdin, 1984). Not only can frustration yield aggression, but it’s also important to note that pain can cause an instinctive aggressive response.
Aggression can also be shaped by accidental reinforcement (Skinner, 1963). It is easy to understand how this might come about; if a dog growls at another dog because he is too close, and that dog goes away, the aggression was successful. Aggression can also be shaped deliberately.
Finally, animals respond more favorably to a consistent environment, so trainers should use caution to condition changes slowly and positively (Turner, 1999). I think this last point is especially important to remember; although we often want quick fixes and miracle cures, the results are ultimately better and longer-lasting when we are patient.
Ken cautioned us that this list is not meant to be all-inclusive. There are likely other general rules about aggression that were either not covered or that scientists are in the process of discovering even as I write this. Although I do not have any references to cite, I would say that in my experience, once an aggressive action enters an animal’s repertoire, it’s always there. The animal may not use that response as the first, second, or third choice, but it can always crop up again. This is why I’m so careful with Maisy, even though she’s basically normal these days.
What about you? Are there general rules you’d add to this list?