There’s one thing that’s consistent at every office around the world: When someone puts free food in the kitchen, people devour it like they’ve never eaten before, and might never eat again.

So some psychologists looked at WHY office workers lust for free food. Here are the three main reasons:

1. It goes back to our prehistoric days. There’s a deep, biological instinct in us to grab food when it’s available. Because if we don’t, we might starve. It’s also why we can’t resist the free samples at the grocery store.

2. We spend our entire lives learning to grab free food that other people are after. It’s why we try to get as much candy as we can on Halloween, or out of a piñata, and why we make sure we’re first in line to get a piece of birthday cake.

If you’ve ever missed out on the food in one of those situations, something clicks, and tells you to NEVER let it happen again.

3. It’s a good bonding experience. Eating with someone builds trust, so it’s a good chance to develop better relationships with your coworkers.