[lobo-tuerto]

It isn't self evident. That's why research and studies are performed.

We can assume or think a lot of things are self evident, but if there isn't any hard facts lying around, we can never be sure.

[sliverstorm]

Ok, self-evident is the wrong word. Properly expressed, what they describe and conclude is exactly what I have experienced all my life. If I stay up all night, or close to all night, the following night I will sleep for 10+ hours. The following night after, another 10+ and the 3rd night 8-9. Not by choice, I just can't be woken by my alarms.

This pattern repeats almost without fail.