If you've ever discovered that a co-worker pilfered the sandwich or leftovers you brought to work, you probably were not a happy camper.

It's all about invading our territory. We stake out space that "belongs" to us, and the more connected or intimate something feels, the more upset people get when another person violates it, says clinical psychologist Carolyn Kaufman.

When it comes to food, you bought it, made it or packed it, put your name on it and someone still took it.

"And if you wrote a note, the person who takes it knows they're taking it from you, so it becomes a personal attack," she says.

So losing your yogurt may be annoying. (Yogurt, by the way, is one of the most popular stolen items, according to food-snatching victims.) But touch your lovingly made sandwich or leftovers, and that's another story.

"There's more intimacy to that and the resentment is even stronger, especially because this is something you're going to put into your body," Kaufman adds.

The culprits do it for several reasons. People think of the company refrigerator as communal — some people figure the food has been forgotten and no one will miss it, she says.

It's also more about a sense of entitlement, a feeling of "If we want it, we should have it now," where the rules don't apply to us, she says. Food and impulse control don't often mix well, either. Then there's the "work owes me" attitude, which can carry into the office fridge.

Add in a lack of accountability and figuring nobody will know it's you.

"Research shows that people do things they otherwise wouldn't when they feel anonymous," Kaufman says.

Rarely will you get caught or in trouble, although I have heard of offices so fed up with food-snatching that workers installed a camera in the back of the refrigerator. But when caught, the perpetrators argue they didn't realize the sandwich was Bob's or they were going to replace it.

The payoff — the pickles, that delectable turkey on rye or leftover Indian — is greater than the punishment. People know exactly what they're doing, says Kaufman, and it may give them a sense of power in a place where they feel they don't have any.

Perhaps letting the perps know you're on to them will help. It wouldn't surprise me if this column ends up on office bulletin boards and refrigerators across America.

E-mail Andrea Kay at andrea@andreakay.com.