Early birds and night owls have radically different daily habits. But a new study suggests they both share one trait: As the clock ticks, their decisions get dicey. Neuroscientists examined the quality of moves in more than 1 million games of chess in an online database. They charted the decisions of 99 prolific players by gauging the time they took for each move and its usefulness in leading to a victory—factors that impact games like high-speed tiebreakers in the World Chess Championships, which took place in New York City earlier this week. As expected, early risers played more games in the morning, whereas night owls were active at dusk and beyond. But both sets of players took longer for each move and made better game choices early in the day and soon after they woke up. Come evening, their game play quickened by 2.5%, while their moves grew less effective by the same margin on average. The study revealed a pervasive switch in decision strategy from safe play in the morning to riskier—faster and less successful—moves at sundown, the team will report next month in Cognition . The finding shows we may have greater control over our decisions earlier in the day and soon after we wake up, regardless of when we prefer to sleep. As we grow tired, our bodies’ need for sleep could dictate the quality of our choices—no matter how focused we think we might be.