I can wake up less than 2 minutes before my alarm goes off regularly.

I read the common wisdom on the subject which says "circadian rhythm; PER proteins; internal clock". I am skeptical of this for two reasons:

  • I go to sleep at night at different times ranging from 11:00 to 2:00 and rarely check the time, so if I don't even know the sleep start time, how can my body measure out the duration of sleep and get the end time right?
  • People's chemical levels vary from day to day depending on a ton of variables (food intake, physical activity, stress, etc). It appears that we are not deterministic machines that are constant from day to day to that level of precision

I have a few hypotheses that I haven't heard before:

  • Maybe the subconscious is queuing off the light level in the room? (this a unique property of the specific minute of wakeup, as there would be less light a minute sooner and more light a minute later)
  • Maybe while sleeping, the eyes periodically open, view the clock, process the numbers, and wake up accordingly (just like people can sleepwalk and use their eyes to process where the walls and doors are)

Any thoughts?

  • 2
    $\begingroup$ Not sure why this is receiving negative voting. If you fail to actually read the post, I'll admit the language (i.e., usage of I ) superficially sounds opinion-focused, but this question is , IMO, asking about a general biological phenomenon that certainly ican be addressed with non-opinion answers. @Noob I think you should add an explicit explanation of what you've already done to ty to answer your own question to help encourage further positive feedback. However, down- and close-voters, I encourage you to provide your rationale for this one since I do not see an issue $\endgroup$ Commented Feb 20, 2021 at 2:32
  • $\begingroup$ When changing the time of your alarm, would you wake up at the same time, or again 2 minutes before the alarm? $\endgroup$
    – tsttst
    Commented Feb 21, 2021 at 20:07
  • $\begingroup$ For what it's worth, this question could come from me - I have exactly the same experience as OP; had it forever. $\endgroup$
    – AnoE
    Commented Jun 25, 2021 at 12:26

1 Answer 1


The biological answer is presumably cryptochromes. The foregoing applies to humans who have CRY2 blue light receptors in the inner retina (the neural layer, not the photoreceptors). I've seen claims these respond particularly well to the light before dawn, though I didn't track those down just now.

That said, a proper skeptic would dismiss this as confirmation bias, at least until proven otherwise.


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