You've probably watched A&E's series Hoarders, which feature homes of suffer from compulsive hoarding. It's a fascinating show, probably because we all can relate to being messy, but these people just take it to a whole 'nother level.
To find out how their brains are different, David Tolin of Yale University School of Medicine subjected hoarders to fMRI brain scans. He found something quite interesting: hoarders don't particularly love stuff, instead they're deathly anxious of making the wrong decision to throw things out, so they keep them all instead.
As Tolin and his co-authors noted, hoarders are not necessarily eager to keep everything they possess, but rather “the disorder is characterized by a marked avoidance of decision-making about possessions.” And the extra activity in the anterior cingulate cortex and insula while evaluating what to do with their own items “may hamper the decision-making process by leading to a greater sense of outcome uncertainty,” the researchers noted. In other words, hoarders might often feel that they are at risk of making a wrong decision—and that that decision could bring with it greater risk than it actually would. “The slower decision-making may be a central feature of impaired decision making in hoarding,” the researchers noted.
Katherine Harmon of Scientific American's Observations blog has more: Link