A question just occurred to me: How much does environment effect sleep preference? When we are in grade school, we have to get up early. In college, we have no one to tell us what to do so most students just sleep until noon if they don't care about classes. In various labs I've worked in, most people don't really get productive until 10 AM which is fine with me. However, in my current lab, things really start up around 8 AM. Just that two hour difference is a bit hard to take. Wouldn't there also be people in the multitudes of shifts in between the extreme day and extreme night shift individuals?
