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Nicholas Dodman
Nicholas Dodman

On Aggression

The rainbow spectrum of aggression across mammalian species

Aggression is the number one behavior problem of humans, dogs, cats, and horses (to name but a few mammalian species). It is a perfectly normal survival-necessary behavior when expressed at the right time and under the right circumstances, but you can sometimes have too much of a good thing.

An excess of any “normal” behavior can be a problem that calls for attention. With this in mind, it is odd that the Diagnostic Manual of Psychiatry (DSM) does not list excessive aggression as a personality problem. Too much anxiety and you have generalized anxiety disorder (GAD); too much fear and you have phobias; too much concern about personal safety and you have obsessive-compulsive disorder (OCD) and so on. But too much aggression and you have – no diagnosis.

Also, there is no medication accepted approved to treat aggression, though psychiatrists get by with extra label prescriptions of, say, selective serotonin receptor reuptake inhibitors (SSRIs) to address the problem when they recognize it in their patients. The lack of an FDA-approved treatments for aggression may be partly because big pharma does not want to risk its deep pockets by launching a specific aggression-suppressing medication.

In animals we call excessive or untoward aggression for what it is using a classification system to separate it into the different types with different motivations. Sometimes aggression can be quite reasonable – like a dog I saw who bit a man who ran his wheel chair over the dog’s tail (pain-induced aggression). As the old adage goes, all dogs may bite. Another case of mine involved a dog that was so aggressive to the male owner that the man had to call his wife on a cell phone when he was 5 minutes away so that she could secure the dog before he walked through the door.

I was once giving a series of lectures with my friend and colleague Dr. Ian Dunbar. Ian asked the 150 person audience “Raise your hand if you have never had an aggressive thought.” No one raised their hand. Then he asked, “Raise your hand if you have never acted on that thought by hitting or pushing someone.” One woman only raised her hand. Ian said, “Bless you. You’re a saint.” People can be aggressive yet we expect our dogs, cats and horses to be perfect – completely aggression free.

Not all people and not all dogs (or cats or horses) only display occasional, reasonable aggression. For some, aggression is a trait not a just an occasional heat-of-the-moment state. Overly aggressive people and animals can have their aggression classified in a number of different ways. The Moyer classification is what is commonly used for domestic animals. Moyer classified aggression as either instrumental, fear-induced, territorial, intermale, maternal, irritable (including pain-induced), or predatory.

Dogs who literally bite the hand that feeds are displaying instrumental aggression. That is, aggression without malice designed to achieve some specific goal, for example, protection of a valued asset – a bone perhaps. Anxiety about what might otherwise transpire is a component of this type of aggression, but it requires some self-confidence, too. People display instrumental aggression – for example, the robber who injures a storekeeper in his efforts to gain access to the cash till. No malice, just business.

Dogs whose aggression is directed toward strangers have what veterinary behaviorists and trainers call fear aggression (fear-induced aggression). Typically men are the targets of such aggression because men tend to be more aggressive and are more likely to frighten a young dog with their bullish ways. Certain types of men – tall men, bearded men, men with baseball hats, men wearing sunglasses – are prime fodder. Of course, dogs are not born with these prejudices, they acquire them. Details about the people who set these dogs off gives a clear view of past events that lead to this (designed to be) dispersive type of aggression. You can almost create an identikit image of the original offender(s) who caused the dog to be fearful in the first place from knowledge of the appearance of people who cause the dog to become aggressive. It’s the same for fear aggression directed toward other dogs; often a class action suit! Aggression caused by fear of harm also occurs in people. A good offense is often the best defense.

Photo from - Creative Commons License
Source: Photo from - Creative Commons License

Dog who are only aggressive toward strangers on their home turf are displaying territorial aggression. I am reminded of a gentle but highly territorial bulldog called Tank who attacked a man entering the home uninvited. No doubt Tank thought he was doing his duty but when that duty inflicted an injury to the man’s arm requiring 18-stitches to repair. Tank was in serious trouble. I do not need to remind you about the territorial nature of humans who fight like cat and dog over even small parcels of land. Imagine there was no country – nothing to kill or die for (John Lennon).

Intermale aggression by dogs and cats is dramatically reduced by castration so is obviously testosterone fueled. It seems that males of all species fight for self-assertion and domination of a potential competitor. These fights can be to the death. I saw on the news the other day that two bucks were found drowned as they locked horns and fell into a stream in mortal deadlock. It all seems so pointless, but it’s nature’s way. Again, I do not need to remind you of the human equivalent. You read about it in the paper every day.

You’ve heard it said “never come between a mother bear and her cubs.” Never a truer word was spoken. Maternal aggression, as reasonable as it may sometimes be, can sometimes get out of hand. A bull terrier bitch I saw became so aggressive after the birth of her litter that her owners seriously considered “putting her to sleep.” Fortunately this was avoided by the temporary use of an SSRI and ovariohysterectomy as the long term solution. Maternal aggression is fueled by prolactin and lasts throughout lactation in all mammals – nursing human moms included.

Some do not classify predatory aggression as aggression because it is performed without a change in affect. A dog killing a rabbit is certainly not angry. Intently focused, yes. Angry, no. Neither is a cat killing a mouse angry as it performs a so-called “quite biting attack.” Sometimes predatory aggression is dogs can be misdirected onto other small dogs or even people. Many a small dog has been killed or injured with a scruff shake designed to break the neck of a prey animal.

Rarely a dog with high prey drive will attack a crying infant – the theory being that the infant appears to the dog as wounded prey that must be finished off. Predatory instincts in people are at the root of angling and hunting in general. Predatory aggressive personality is a term that has been used to describe human psychopaths and sociopaths who consider others inferior creatures and therefore their rightful prey.

A favorite axiom is “the more I learn about humans, the more I love my dog.” It’s certainly true that is safer to meet a huge dog lurking in a dark alley than another human being. The average dog is nicer than the average person (Andy Rooney). But I have another axiom as I traverse the fields of animal and human behavioral issues: There is only one medicine, one psychology, one psychiatry across the species. Sure, there are knit picking species differences but the similarities are overwhelming. We are, after all, all mammals on this planet together and have a very similar genetic blueprint.

When there is no enemy within, the enemies outside cannot hurt you – Winston Churchill

About the Author
Nicholas Dodman

Nicholas Dodman, BVMS, DACVA, DACVB, is the former director of the animal behavior clinic at the Tufts University Cummings School of Veterinary Medicine and a pioneer in the study of OCD in dogs.

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