"Alcohol reduces our ability to think straight," says Professor McMurran, a psychologist at the University of Nottingham. "It narrows our focus of attention and gives us tunnel vision.
"If someone provokes us while we're drunk, we don't take other factors into account, such as the consequences of rising to the bait. This can lead to violent reactions from people who would usually shrug things off."
Alcohol also reduces anxiety, which can be one of the reasons we enjoy drinking. But, according to Professor McMurran, anxiety actually protects us by telling us to avoid or escape certain situations. "When we're drunk, this warning system doesn't work and this can put us in dangerous or confrontational situations."
The way we process information is affected when we've been drinking too. We're more likely to misinterpret other people's behaviour and misread social cues. This could be the reason why so many drunken fights start over little more than a 'dirty look'.