Attention, pack rats: science may have figured you out. Researchers say they've found an area of the brain that seems to govern the urge to collect. For most people, collecting is a perfectly healthy behavior. It's an outlet for expressing passion for just about anything, such as stamps, wine, art, shoes, or Elvis memorabilia. Collecting is also common among animals, and not just for food. It's been observed in creatures great and small, from mammals to insects. For instance, some birds can't resist aluminum and bright objects, while hamsters gather glass beads when given the chance. But in rare cases,...