Controversial theory suggests there’s three little-known traits in kids who grow up to be serial killers

Psychologists once revealed three very specific behavioural traits in children that were identified as being early warning signs of sociopathy.

Known as the 'Macdonald Triad', the theory was prominent in the mid-century, but looking back at it through a modern lens, it's clear that there are several limitations to it, namely that it is considered by psychologists to be an oversimplification.

However, with that said, it remains an important concept in forensic psychology and criminology for several reasons, including providing an early intervention insight, deepening the understanding of trauma and abuse links, acting as a catalyst for continued research and viewing it as a stepping stone in the evolution of behavioural science rather than the be-all and end-all of the discipline.

What is the Macdonald Triad?

The Macdonald Triad hypotheses three signs in children that suggested a possibility of adult violence (Getty stock images)

The Macdonald Triad, which is known as the Triad of Sociopathy, is a theory proposed in the 1960s by psychiatrist J.M. Macdonald in his 1963 article, 'The Threat to Kill', published in the American Journal of Psychiatry.

Macdonald's clinical observations of 100 patients who had threatened violence formed the basis of this theory.

In short, it suggests that three specific childhood behaviours may be early warning signs of violent or antisocial tendencies later in life - particularly in relation to serial offending.

But what are these behaviours?

Well, according to the theory, they include cruelty towards animals, an obsession with setting things on fire and chronic bedwetting that doesn't seem to go away.

Animal cruelty

The Macdonald Triad points to animal cruelty as a major warning sign (Robin Gentry / Getty Images)

Repeatedly harming or killing animals in childhood can indicate a lack of empathy or enjoyment of domination over weaker beings, such traits which can sometimes be seen in violent offenders.

Psychologists at GetLabTest.com warn that animal cruelty is perhaps the most concerning of the three behaviours, which can range from intentional neglect to direct physical abuse of animals.

"While this behaviour is indeed troubling and requires immediate intervention, it's important to note that not all children who harm animals become violent adults, and not all violent adults had a history of animal cruelty," the experts outline.

Fire-setting (pyromania)

Pyromania was also listed in the theory proposed by psychiatrist J.M. Macdonald in 1963 (Mariano Sayno / Getty Images)

An obsessive fascination with or compulsion to start fires may reflect underlying anger, a thrill-seeking behaviour, or a need to assert control.

However, the experts note, many children who experiment with fire do so out of curiosity rather than malicious intent.

Persistent bedwetting (enuresis)

Frequent bedwetting beyond the typical developmental age, which is usually past age five, isn’t violent itself, but in the triad theory, it’s linked to stress, humiliation, or poor emotional regulation.

While this trait was included in the triad based on observations of adult offenders, modern research shows this is more likely a symptom of childhood trauma or developmental issues rather than a predictor of future violence, the experts point out.

What are the limitations of the Macdonald Triad?

In the triad theory, persistent bedwetting is linked to stress, humiliation, or poor emotional regulation (jes2ufoto / Getty Images)

Modern psychology views the Macdonald Triad as controversial, with many experts arguing that these factors alone don’t necessarily cause violent behaviour but that they may instead signal underlying trauma, abuse, or emotional distress that requires attention and care.

Healthline also says that Macdonald himself didn't believe his research showed a definitive link between these behaviours and violence later on in life.

According to GetLadTest.com, experts now view the Macdonald triad as overly simplistic because it lacks strong scientific evidence supporting its predictive value, with research showing that these behaviours are 'more likely indicators of childhood trauma or distress rather than reliable predictors of future violent behaviour'.