In fact, research shows that knowledge workers actually have fewer good hours in a day than manual laborers do — on average, about six hours, as opposed to eight
The other thing about knowledge workers is that they’re exquisitely sensitive to even minor sleep loss. Research by the US military has shown that losing just one hour of sleep per night for a week will cause a level of cognitive degradation equivalent to a .10 blood alcohol level.
"Bring Back the 40 Hour Work Week" by Sara Robinson
Scroll to the end — really interesting that our current definition of “good” workers is based on the mental illness of early Silicon Valley tech workers. Awesome.
Bit of Trivia: productivity experts agree that we’d have the original Mac a year earlier if they’d worked 40 hours instead of 90. Ha!