When our mind gets too much information, we either ignore most of it or group it into chunks. This is how we make decisions about information really quickly, and our brains are hardwired this way. When we were troglodytes, we had to make a rapid decision when something jumped in front of us to either run away or club it on the head. We are simply not able to process all the details of a situation, so we group things based on their characteristics, and use the nature of the group itself to decide what we should do with it. This is the only way we have of surviving the complex world we live in without sitting and thinking about everything for hours at a time.