The bias toward early birds

According to Weiss, chronotype refers to people's natural sleep patterns, and they are often divided into two categories: early birds for people who typically wake up early and night owls for those who tend to stay up late.

In general, "[i]t doesn't take long to see which team more often comes out on top," Weiss writes. So far, research suggests that early risers are happier, more punctual, and do better in school. In comparison, night owls are more likely to be impulsive, angry, have poor diets, and become cyberbullies.

There's also a clear bias toward morning people compared to evening people, even outside of scientific research. According to Declan Gilmer, a Ph.D. student at the University of Connecticut who studies workplace psychology, "[i]f someone gets up at 6 a.m., and they show up at work early, they're viewed potentially as more committed."

In his 2018 masters' thesis, Gilmer found that when participants were acting as managers, they rarely treated chronotype-related scheduling requests, such as starting and ending a workday later, as legitimate. And when night owl employees made these requests, participants viewed them more negatively, even though they were just as productive as early bird employees.

These findings have also been supported by more recent research. In a study published in Behavioral Sleep Medicine, researchers found that people "perceived night owls as significantly more lazy, unhealthy, undisciplined, immature, creative, and young."

Why chronotype research may be lacking

According to Weiss, it is unlikely that humans can be categorized so neatly by their sleep preference, and the research may be "painting an incomplete and overly moralistic picture."

Although researchers often focus on just early birds or night owls, sleep preference is actually on a spectrum rather than a binary, with everyone always on one side or the other.  

"I think most people would recognize that, in reality, [chronotype is] more of a continuous type of variable," said Brian Gunia, a sleep researcher, professor, and associate dean at Johns Hopkins' Carey Business School.

Although chronotype has biological and genetic roots, it is "far from fixed," Weiss writes. A person's sleep preferences can change with age. In addition, the personality or physiological traits that are supposedly associated with a certain chronotype can change throughout the day.

According to Gunia, the time of day in which a study is conducted can influence the findings significantly. For example, a 2014  study of chronotype and ethical behavior found that early birds were most ethical in the morning while night owls were most ethical in the evening.

"[M]aybe it's more of a fit between chronotype and time [of day] than it is this idea that morning people are better or worse," Gunia said, noting that studies that don't account for the time of day "are missing half the equation." (Weiss, TIME, 5/25)

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