"In their relative evening, late risers are more alert and can outperform early birds in a reaction time test assuming they're allowed follow their natural sleep rhythm, whereas there are no such differences in the morning" would be a more accurate title...

The paper also gives insights relative to the neural processes involved.

There's that term again. How do we know that real life "early birds" and "late risers" are actually following their natural sleep rhythms?

Some do, some don't. Most people go back to their natural patterns during the holidays, though. The classification is based on forms asking questions in a context of freedom from external constraints.

I'm not very familiar with sleep research, but I'd guess that both types will underperform if their natural penchant is disturbed (by work hours, for example).

Edit: Here is the actual screening form (in French) used for the studies: http://www2.ulg.ac.be/crc/in/CIRCADIEN_ONLYweb.html ... Adapted from: Horne, J. A. and O. Ostberg (1976). "A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms." Int J Chronobiol 4(2): 97-110.

Extreme early and late subject are further "diagnosed" with more exhaustive tests.

Interesting, thanks.

I do want to make it clear I wasn't trying to attack the study so much as explain why people get upset and respond to something like this with anecdotal comments.

It was clear, to me at least :-).

I'm not sure where your perceived disconnect between mental stamina and running out of steam is. (Additionally, could you say how mental stamina is a bad thing, ceteris paribus?)

Could you elaborate on your definitions for "early bird" and "night owl"? My everyday semantics align with the article.

My comment was mainly to point out the lack of context, and could have been clearer. But mental stamina may not be a good thing emotionally, that isn't really explored. The term mental stamina is fine, since that's what the study was about, but the first paragraph over-emphasizes the value judgment in order to antagonize and stimulate argument. So with an article like that, don't expect the responses to be intellectual.

Could you elaborate on your definitions for "early bird" and "night owl"? My everyday semantics align with the article.

An early bird, to me, is someone who likes getting up early and usually does. An early bird, according to the study, is someone whose natural circadian rhythm is shifted earlier in the day. A night owl, to me, is someone who regularly stays up late. According to the study, it's someone whose natural circadian rhythm is shifted later in the day.

In everyday use, night owls include people who stay up late and sleep late because they like getting hammered. In everyday use, early birds include people who force themselves out of bed at the crack of dawn with an alarm clock and a cup of coffee. In every day use, the terms apply to people who may spend significant portions of their day engaged in physical activity. None of those people fit the definitions used by the study (as I understand it, anyway)