The Macdonald Triad was first presented in the sixties as a way of predicting violent behavior. Today, people are not so convinced. We'll take a look at the rise and fall of this particular way of predicting whether kids would grow up to be serial killers.
If you've watched any crime shows, you've heard at least a few references to the Macdonald Triad. Whether a psychologist was mentioning it to bolster the evidence against a suspect or dismissing it as a foolish fad, it can't be entirely shaken. It's pop-culture friendly because it's so simple. The Macdonald Triad describes three behaviors that, when taken together or separately, are predictors of violent tendencies during adulthood. Sadistic behavior towards animals, fire-starting, and persistent bed-wetting beyond the age of five are signs that a child will become a murderer. The triad was first proposed in 1963, in the American Journal of Psychiatry by J. M. Macdonald.
There certainly have been some violent adults who fit any one of these criteria. Multiple serial killers exhibited fire starting and animal cruelty as children. And the 1966 book, In Cold Blood, revealed that one of the killers of a family persistently wet the bed, though Capote might have emphasized this only because he'd heard of the triad.
While none of these behaviors are good news for parents, how did they become the trinity of violent psychology? Macdonald never claimed any predictive power in the traits. He only observed that in a hundred-person study of both psychotic and nonpsychotic patients, all of whom had only threatened to harm someone, these traits disproportionately showed up. Another group of psychiatrists studied a little over a hundred convicted violent and non-violent offenders, most of the violent offenders had one trait, and forty-five percent had all three.
This got a bigger ball rolling. Most people who conducted similar studies found that the results were not reproducible. The FBI's Behavioral Analysis Unit was one of the few institutions which found that they were. Their study of thirty-six murderers, twenty-five of which were serial killers, caused them to both make it a policy to look for people with some of those traits in the background. Many people who had been with the FBI published books in which the triad was mentioned. Most psychologists agree, though, that the studies were not properly randomized, and so each of the traits were more likely to be correlated with the killers' childhood circumstances than outright predictors of violence.
Of the claims, the most roundly refuted is bed-wetting. Modern studies do not find any correlation between bed-wetting as an older child and violence as an adult. Still, it's only in the past decade and a half that the triad has been seriously challenged.
The idea that we can find the seeds of an adult serial killer in the behavior of a child is, in some ways, a hopeful one. A child is still growing, and might be helped in positive ways to become a nonviolent person. It doesn't look like we've actually pinned down a reliable source yet.
Via Psychology Today.