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)