Blame Your Sloppy Decisions on the Time of Day

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Photo: Ignacio Adasme Photography/Getty Images

It’s not just your office that will make you think that everybody gets messier as the day wears on: According to a small, fascinating study of chess players, decision styles are yoked to the time of day.

In an upcoming study covered by the Association for Psychological Science’s Minds for Business blog, researchers tasked a hundred-some online chess players with a quiz about their time zone, how much they felt they were morning people or night people, and a couple of questions about their sleeping and eating habits. Simulated computer players served as a control group.

The research team, lead by María Juliana Leone at the Integrative Neuroscience Lab, did find one big difference between the morning people (larks) and the evening people (owls): The larks played more games earlier in the day, owls more later in the day. But, contrary to their hypothesis, both larks and owls shared in the quality of play decisions they made as the day wore on.

“We found that players changed their decision-making policy throughout the day: players decide faster and less accurately as the day progresses, reaching a plateau early in the afternoon,” the researchers are quoted as writing.

Regardless of whether participants identified as a lark or an owl, everybody tended toward a slower, more accurate (as evaluated by an algorithm) style during the morning, and a riskier, faster, and less accurate style in the evening — contrary to earlier research that found that morality in decision-making depends on your larkiness or owlness.

While more work will need to be done to see if this generalizes to a work environment, it does seem to corroborate my own anecdotal research: The longer the day goes, the fuzzier the brain gets. For everybody.