While there is a certain grand mystery to some aspects of human behavior, others can be easily explained. Just find yourself a garden-variety house cat, along with a $10 laser pointer.

Many cat owners know that the lasers are the easiest way to keep the pet amused. The cats will ceaselessly, maniacally chase it as it's beamed about the room, literally climbing the walls to capture what they surely regard as some form of ultimate prey.

Obviously, cats are hard-wired to hunt down small, bright objects, like birds. But since nothing in nature is as bright as a laser, they are powerless to resist its charms.

Cats and lasers are useful in explaining some of the more addictive aspects of Web use, including a recent occurrence on the site for Andrew Sullivan, a popular political blogger. Mr. Sullivan's blog doesn't follow the standard practice of making room for readers to add their own comments after each blog item. Curious if he should change his policy, he put the question to a vote.

Readers responded 60-40 against allowing comments. Even more striking than the fact that these readers were denying themselves a voice was the reason some of them gave for declining the offer: Like cats chasing a laser, they wouldn't be able to stop themselves.