Scientists believe that your brain has a built-in “negativity bias.” In other words, as we evolved over millions of years, dodging sticks and chasing carrots, it was a lot more important to notice, react to, and remember sticks than it was for carrots.

That’s because – in the tough environments in which our ancestors lived – if they missed out on a carrot, they usually had a shot at another one later on. But if they failed to avoid a stick – a predator, a natural hazard, or aggression from others of their species – WHAM, no more chances to pass on their genes.
(more…)