Why is it harder to stay asleep when you go to bed at an earlier time than your normal bed time (i.e. 7pm rather than 11pm)?

Question

Why is it harder to stay asleep when you go to bed at an earlier time than your normal bed time (i.e. 7pm rather than 11pm)?

In: Other

Answer 1

The ‘sentinel theory’ suggests that humans can train themselves to sleep during a certain time of day because our ancestors would have been preyed upon and only felt comfortable sleeping when others were taking watch. So individuals slept and guarded in shifts instead of collectively sleeping at a certain time.