Lethal violence
Pathways to tragedy
Image: training material for Health Professionals - https://slideplayer.com/slide/14245419/
Humans kill other humans. But why? This series aims to investigate this mystery. Are murderers bizarre anomalies, or are there pathways that make people more likely to murder? In this piece, we look at the evidence that there are two fundamental types of aggression; two different pathways to homicide.
Colin Bouwer, a psychiatrist, moved from South Africa to Dunedin, New Zealand in 1997 to take up a job at the Otago University Medical School. With the benefit of hindsight, it would have been smart of his University of Otago employers to do reference checks. They would have found that he’d been suspended by the South African Medical Council for 10 years from 1982 due to his abuse of the opioid pethidine.
While attending an international conference Dr Bouwer began a relationship with a colleague. Soon after his return to Dunedin Bouwer’s wife (his third) developed symptoms of dizziness, blurred vision and problems with coordination. These are symptoms of hypoglycemia (low blood sugar). She died, despite medical care and hospital stays.
In a university tutorial, Bouwer had previously told students that injecting insulin between the toes could ensure a perfect murder. Insulin is a glucose-lowering drug that causes symptoms of hypoglycemia in healthy people but is quickly metabolised and not picked up in standard blood tests. Bouwer wrote prescriptions for glucose-lowering drugs during the time his wife was ill. The day before his wife died he picked up a 1,000-unit vial of Humalog insulin – a dose sufficient to kill her.
The jury took just three hours to convict him of murder.
Manawanui Stewart, a young man from Wellington’s Kapiti Coast was a regular at alcohol-fuelled fighting sprees along a back street in Paraparaumu. In August 2012 the 26-year-old caught up with Izak Wikaira Millanta, a 17-year-old he had previously fought.
Both had been drinking, Stewart struck Millanta several times before going back to a bar. On his return, he was involved in another fight. Millanta was still on the scene with a friend, and Stewart approached and hit the friend and told Millanta to leave. Millanta took off and Stewart and another followed, and attacked, knocking him to the ground and stomping him. Millenta died in the hospital.
Stewart was found guilty of manslaughter.
Murder or manslaughter?
The Te Ara encyclopedia distinguishes the crimes of murder and manslaughter. Murder is a deliberate act or a reckless act which the perpetrator knows could result in death. Manslaughter is the result of an unlawful act, but where death could not reasonably be expected.
Bouwer’s deliberate actions were seen by the jury as murder. Stewart’s assault on Millanta could be seen as an unlawful act that would not necessarily result in his death.
There are two varieties of aggression, one is more an impulsive reaction to a threat, the other a planned attack to fulfil a goal.
A hot-blooded reaction to disrespect for example versus enacting a well-planned, goal-oriented, cold-blooded attack.
There is not a perfect correlation, but the legal distinction between murder and manslaughter is a reasonable match to what the scientific evidence indicates as the real distinction between respectively proactive and reactive aggression.
The brains of proactive and reactive aggressors
Researcher Luke Broomhall from the University of West Sydney set up a simple card game (along with a suite of other tests) for 25 violent offenders. They chose cards from 4 packs – each with 40 cards. The chosen card resulted in a win or a loss. Two of the packs were ‘good’, two ‘bad’. In the bad packs, the rewards from winning cards were larger, but there were larger and more frequent penalties for losing cards. In the good packs, the cards provided smaller but more frequent rewards and fewer, smaller penalties.
This gambling test has a strong track record. Previous research has found that after about 10 trials healthy adults demonstrate a physiological reaction when their hand hovers over the ‘bad’ packs. It takes about 40-50 trials though before these people can say which are the good and bad packs. Is there a part of the brain not accessible to consciousness providing emotional clues faster than the logical reasoning centres of the ‘smarter’ cortex?
The two parts of the brain implicated are the amygdala – a deep brain centre which identifies threats, and the orbitofrontal cortex – directly behind the eyes, a brain zone involved in decision-making. The amygdala intuits there is an issue with the bad decks, the orbitofrontal cortex modifies its decision-making a little later. People with damage to the orbitofrontal cortex keep picking cards from the bad decks, even when they can articulate that they are losing.
Broomhall carefully distinguished reactive from proactive violent offenders from a review of their offending history (were they impulsive offenders or were they more ‘instrumental’ – more goal-oriented in their offending).
The reactively violent offenders did worse on the gambling test. The researchers spell out the implication: “the primarily reactive group was more guided by their immediate prospects and generally insensitive to future consequences of their actions.”
What of the proactive individuals? They typically did as well on the tests as the healthy people who make up the ‘standardisation’ comparison. But they had an issue with one aspect of the test. They continued to be attracted to the high-risk and high-reward (‘bad’) decks. This is a similar pattern to patients with damage to the amygdala–frontal cortex pathways. For these people, it seems harder to get the messages from the amygdala up to the front of the brain to hold back reactions to dangerous or threatening signals.
The takeaway – much violence follows one of these two tracks – impulsive, hot-blooded reaction or cold and deliberate attack. The reactively violent may have difficulty seeing beyond the immediate issue and factoring in the long-term consequences. The proactive offenders may understand the odds but because the danger signal is dialled down, they may choose not to inhibit their action (what Broomhall described as “selective impulsivity”).
Pathways to violence
Some clues are provided by the work of Adrian Raine and colleagues in developing the Reactive-Proactive Aggression Questionnaire. As part of the Pittsburgh Youth Study, they surveyed a group of 7-year-old boys (about 51% Caucasian, 49% African-American) – who filled out questionnaires, while their parents and other caregivers also reported on their behaviour. Nine years later they repeated the process with the now 16-year-olds.
The fundamental result – there was a difference in the pathways of violence – some began and persisted as reactively violent, while others followed the proactive trajectory.
Some clues to the different patterns, in items from the questionnaire:
Reactive violence:
Damaged things while mad
Felt better after hitting
Hit when teased
Proactive violence:
Carried weapons for use
Threatens and bullies
Vandalised for fun
The theme from the behaviour of reactives as indicated by these (and other) items is an impulsive reaction to provocation. For the proactives, a theme is their use of violence, or its threat, as a means to an end.
Considering meaningful patterns with other measures, there were clear differences.
The reactive were more impulsive, more anxious, and experienced reality distortion and information-processing abnormalities. This would make dealing with the complexity of social relationships more difficult for them.
The proactive had poorer social backgrounds (lower social class, poorly educated and unemployed father, substance-abusing parents, single-parent status), poorer peer relationships and were more seriously violent. As a simplification, proactive individuals have learned that violence is a way to get what is not otherwise accessible.
It's not quite that simple
A recent review emphasises that while the reactive/proactive distinction is real, people don’t fit neatly into one or another box. Reactivity and proactivity are tendencies to which people are more or less disposed. It is possible to be low on both (as I hope you are reasonable reader). Or, worryingly, also possible to be high on both. I have tried to illustrate this with a simple 2-by-2 matrix:
A two-dimensional view of proactive and reactive violence
Colin Bouwer told incredible lies – in casual meetings he would describe being tortured by the South African secret police (in fact he was employed by the South African military). Some of these stories were readily found out. The doctor who visited his house to sign the death certificate recommended an autopsy, but Bouwer responded that he and his wife were Jewish and so it was necessary to have a rapid burial. The service for Bouwer’s wife was led by an Anglican priest – the doctor attended and then began his push for a full investigation. Bouwer’s readiness to lie fits with Broomhall’s finding of proactives’ readiness to make risky moves in the gambling game.
When the police searched Bouwer’s house they found the pestle and mortar he’d used to crush the insulin and other glucose-lowering medication behind the Weetbix in the pantry. This sloppiness fits more with not thinking ahead – acting to solve the problem right now.
Stewart’s action in chasing his victim could be seen as evidence of cold-blooded predatory intent, rather than reactive lashing out. For both of these individuals both reactive and proactive inclinations appear to be in play.
You will have noticed that the emphasis so far has been on the head and not the heart of the offenders. We have considered brain function (and lack of it), but not the empathy, or lack of it, of the offenders. Both Bouwer and Stewart would have seen and heard the suffering of their victims. But this did not hold them back.
A brain-imaging (MRI) study of violent adolescents (and healthy controls) indicates what might be going on. As might be expected there was a relationship between reactive violence and reactivity in brain areas associated with the threat. Smaller areas of the brain areas associated with empathy were related to measures of proactive violence. Proactives have less of an empathy response. They are cold-hearted. We will explore the implications of this in a future piece.