Intelligence Violent behaviour decreases as IQ rises

[Maciamo]

Association between intelligence quotient and violence perpetration in the English general population

A 2019 study published in Psychological Medicine examined the relationship between intelligence and violence perpetration in the general English population. Conducted by Louis Jacob, Josep Maria Haro, and Ai Koyanagi, the research drew on data from the 2007 Adult Psychiatric Morbidity Survey, a nationally representative sample of 6,872 adults aged 16 and over living in England.

What Did the Study Measure?​

Violence was defined broadly but practically: participants were asked whether they had been in a physical fight or had deliberately hit someone in the past five years. IQ was assessed using a standardized cognitive test, and participants were grouped into IQ bands ranging from below 70 to 130+.

Key Findings​

The results showed a clear and steady inverse relationship between IQ and violent behavior:

• IQ 70–79: 16.3% reported violent behavior
• IQ 80–89: notably elevated rates
• IQ 120–129: only 2.9% reported violent behavior

In other words, as IQ increased, the likelihood of engaging in violence dropped — consistently and significantly across every band.

Important Nuances​

This kind of study doesn't establish causation. A lower IQ score doesn't "cause" violence. Rather, IQ is likely acting as a proxy for a cluster of related factors, such as:

• Socioeconomic disadvantage, which affects both cognitive development and exposure to violence
• Impulse control and executive function, which are partly captured by IQ tests
• Access to education and social resources, which shape conflict-resolution skills

The study also relied on self-reported violence, which introduces potential underreporting bias, particularly at higher IQ levels where social desirability effects may be stronger.

Why Does This Matter?​

The findings reinforce a well-established pattern in criminology: cognitive ability is one of several meaningful predictors of antisocial behavior. However, it is far from the only one — and arguably not the most important. Structural factors like poverty, trauma, and community environment play an enormous role. Policies aimed at reducing violence are therefore most effective when they address the root conditions that simultaneously depress cognitive outcomes and increase the risk of violent behavior, rather than treating IQ as a fixed destiny.

 

[Tigertim]

Or we could just stop mass importing people from low IQ countries and keep the native inhabitants safe.

 

[Maciamo]

Or we could just stop mass importing people from low IQ countries and keep the native inhabitants safe.

True, but there are also plenty of low IQ people among the "natives".