There’s a link to the relevant column in Engineer Dude’s post, about 12 posts above yours. Click on the link to read the column.
I’d be willing to wager heavily that its a body clock and conditioned response thing. I can’t see the face of my alarm (the light bothers me so I turn it towards the wall) and I absolutely, positively utterly HATE being woken by the alarm. Any alarm. Loathe it. So I always wake up before it can go off. And I know it has to be my body doing the waking cause on more than one occasion I forget to set the alarm and I still wake in time, and my schedule is varied (that is to say,the time I have to get up changes depending on the day). I just basically say to myself "Must get up by such and such time and boom. Im up. Only time that doesn’t happen is when Im REALLY tired. As in little or no sleep for several days in a row.
Interesting note: I have 3 digital alarm clocks, one by my bed, one on my dresser, and one extra loud one in my living room, which I get away with since I currently live by myself. I am NOT a morning person by any means, and usually it takes all 3 to get me rolling on the average day. The one in my living room sits on an end table right next to my cell phone charger. During the rare instances that the first 2 alarms did the trick and I was in the living room before the 3rd went off, I’ve noticed that about 10-15 seconds before it goes off, my cell phone speaker starts to crackle.
An interesting experiment for someone who commonly wakes up before the alarm and who does not live by himself would be to have someone else vary your alarm’s time within about 10 minutes every day for a week or so, and see if that changes whether you wake up before your alarm.
I’m at the point where, if I’m a fairly regular schedule, I never need an alarm clock at all, regardless of when I got to bed. This is a very nice thing. I hate waking up to an alarm; I use the clock radio anyway and have it set to static turned to low volume, but I still don’t like that. Waking up on my own: much nicer.
But, yeah, even when I do have to use the alarm–say, I have to get up way earlier than usual–I often wake up before it goes off. Also nice.
I typically wake up about 20-40 minutes before my alarm goes off, annoyingly enough. This is probably a little more than half the time… the rest of the time it’s divided between waking up about two hours before the alarm and not being able to get back to sleep, and waking up right when the alarm goes off.
I always sleep with my fan on (I can’t stand total silence), so that probably covers up an Pavlovian “click” my clock may make…
I always wake up a few minutes before my alarm as well, and I wonder if it’s related to my ability to know when it’s 23 minutes after the hour. Just an accurate internal clock.
I think body clocks are really powerful. I’ve been pretty successful with telling myself before going to sleep when I have to get up, and then getting up at that precise time. I haven’t kept track, but I think it’s successful a fairly large majority of the time. When an alarm clock is set, I generally get up one to five minutes prior to when it’s supposed to go off, I think because I hate waking up to alarms. If my subconscious can wake me up at 6 am if that’s what I say before going to sleep, I guess it can tell when it’s five minutes before the buzz-killing alarm clock goes off.