Dogs are allowed in our office at work. When I started taking our dog to the office, I wondered about a productivity drop, what with poop breaks (for the dog) and the dog wanting the occasional bit of attention. It's hard to empirically measure, but I'm pretty sure I'm more productive. Even just turning to pet the dog, and take a break from staring at the screen for a few minutes is helpful. Hourly walk breaks, instead of sitting staring at the screen until lunch, clears my head and gives me a new perspective on a problem sometimes.

Of course you don't need a dog. Just get your ass out of the seat once in a while. It's just easier to remember when something is pawing at you. :-)