A short article in Scientific American entitled “Tough Choices: How Making Decisions Tires Your Brain” looks at “executive function.” A growing body of psychological and neurological studies demonstrates that the human mind has a limited amount of decision making juice available each day.
When said juice is used up decision making declines markedly in measurable ways. Given that software development is an all-day exercise in decision making, trade-off resolution, and implementation (all topics discussed in the article), the evidence cited in the article supports the idea of Sustainable Pace (the idea, nay fact, that programmer productivity goes down past about 40-50 hours of work per week).
The human mind is a remarkable device. Nevertheless, it is not without limits. Recently, a growing body of research has focused on a particular mental limitation, which has to do with our ability to use a mental trait known as executive function. When you focus on a specific task for an extended period of time or choose to eat a salad instead of a piece of cake, you are flexing your executive function muscles. Both thought processes require conscious effort-you have to resist the temptation to let your mind wander or to indulge in the sweet dessert. It turns out, however, that use of executive function a talent we all rely on throughout the day draws upon a single resource of limited capacity in the brain. When this resource is exhausted by one activity, our mental capacity may be severely hindered in another, seemingly unrelated activity.
So, scientific study is bearing out what good programmers know implicitly and what great programmers incorporate into their lives. Working longer actually leads to poor decisions and negative productivity; working at a sustainable pace optimizes productivity.