What's the Latest Development?

Not all waking hours are created equal, particularly when it comes to business. The longer you stay up, the more your returns diminish. We've known this for a long time. Studies done as early as the 1880s demonstrate that after 40 work hours per week, productivity declines because we spend more time fixing our mistakes, which we make due to our fatigue. "It seems so logical that two units of work will produce twice the output," says entrepreneur and author Margaret Heffernan. "Logical but wrong."

What's the Big Idea?

There are sound physiological reasons for why staying awake longer means poorer productivity. When you become fatigued, your brain's thalamus becomes more active, expending energy just to keep you awake. At the same time, your parietal and occipital lobes, which are responsible for processing sensory data, lose glucose, making it harder to concentrate and make accurate judgements about the world around you. When you are low on sleep, you are bound to have a bad temper, bad diet and make bad decisions.

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