If nobody else is home or awake, it's coding time. If anybody else walks in, they want to "talk" and stuff, and that really drops productivity to almost nothing.
There is nothing worse than spending 30 minutes trying to type faster than you think with 10 different tabs open on Eclipse, all edited when someone walks in and asks a question, twice, and starts actually expecting a response. Just to send the message, I like to silently put the keyboard down, slowly cross my legs, look up to them in stages, and say "now... what?"
You would think that after a solid minute of talking into the side of someone's slowly nodding face they would get the clue on their own, but apes are persistent. Sheeeeesh!