Whether it’s criticism calmly dispensed by a teacher at school, or a cruel comment hurled in the heat of an argument with a friend or lover, we tend to remember criticism far better than positive comments, due to a phenomenon called the negativity bias.

In fact, a whole host of complex effects can be explained by this bias, which is the universal tendency for negative emotions to affect us more strongly than positive ones. It causes us to pay special attention to threats and exaggerate the dangers, according to Roy Baumeister, a social psychologist at the University of Queensland and co-author of The Power of Bad: And How to Overcome It.

While a focus on the darker side of the world around us may sound like a depressing prospect, it has helped humans overcome everything from natural disasters to plagues and wars by being better prepared to deal with them (although there is evidence that optimism can also help to protect us from the stress of extreme situations). The human brain evolved to protect our bodies and keep us alive, and has three warning systems to deal with new dangers. There’s the ancient basal ganglia system that controls our fight or flight response, the limbic system which triggers emotions in response to threats to help us understand dangers, and the more modern pre-frontal cortex, which enables us to think logically in the face of threats.