It’s down to the effect of alcohol on one particular area of the brain. The prefrontal cortex is important for keeping impulsive behaviour under control. Alcohol interferes with this, leading people to show poorer judgment and worry less about the effects of their actions. They misinterpret people’s intentions and easily lose their temper. Low levels of serotonin (a moodbalancing chemical) and higher levels of dopamine (a chemical relating to pleasure) are also associated with alcohol-induced violence, but not everyone is affected this way. Expectation and upbringing are important factors, too. Adversity in early life can decrease serotonin levels, while drinking when young can damage the brain’s frontal lobes. Also, people who witness alcohol-fuelled violence as children are more likely to become violent when drunk.