Last night, the colour of a dress seduced the Internet. Yes, it was a cool optical illusion. Yes, other than Victoria's Secret Swim Special there wasn't much on TV that night. But the real reason the dress continues to captivate our attention is because humans love to form groups based on often trivial similarities. Once we form these groups, we love to fight with outsiders. People were more interested in pledging allegiance to #teamwhiteandgold or #teamblueandblack than reading about the science behind the photo.