Movement compulsions may fall into the categories of magical thinking or perfectionism. A person who has movement compulsions may feel as if he must repeat the same action — crossing a threshold, for instance — over and over until he feels he has gotten it “right.” Such compulsions will sometimes “generalize”: it won't be enough to worry about thresholds; soon, the sufferer adds stairs, pathways, and so on.
Just as some people feel compelled to avoid certain objects or situations, others feel compelled to touch things. A person who has a touching compulsion might feel as if she absolutely had to touch the same fire hydrant on the way to work each morning for “luck,” or to feel “okay.” Sometimes, a person with a touching compulsion can't remember why she began the behavior in the first place. She only knows that she would find it very uncomfortable to try to stop.
People who are obsessed with order often have to throw things away with regularity to consider their environments free of clutter. Others wouldn't think of discarding anything that might one day prove valuable. People who hoard valueless things such as empty cereal boxes, soap wrappers, or even “collections” of ordinary objects believe they will one day need them, or that these items may become valuable over time. (Witnessing the astronomical growth of the “collectibles” market, one might have to conclude that this is, indeed, possible!)
Discarding things is painful to such persons and, frequently, their homes become dangerously full. Threatening the person with eviction or tossing out his possessions usually won't work (apart from the legal and moral questions such activities would raise): The behavior will only start again in a new situation, driven as it is by the compulsion to hoard.
Often, people who hoard not only refrain from throwing things away, but also actively go out in search of new objects to add to their collections. Sometimes, they intend to restore these things for future use or to render them helpful to others. In a great majority of cases, the objects they take home would be considered “junk” by most people.
It Can Even Be Hazardous
From time to time, you will probably see a news story about an unfortunate person who died when his house went up in flames, and firefighters couldn't reach him for all the mountainous piles of newspapers or other clutter. Or maybe there's a house in your neighborhood that's considered a hazard because of all the junk (or even bona fide garbage) in and around it. Perhaps that describes your own home. Obsessive hoarding may be the cause.