In one famous study, judges approved parole in about one third of the cases they heard. But as with most averages, the proportion did not hold steady hour after hour throughout the day.
As a matter of fact, prisoners who appeared before judges early in the day were paroled about 70% of the time and those who appeared later in the day were paroled only about 10% of the time.
The cause? Low blood sugar.
It turns out that when we describe ourselves as mentally ‘drained’, we are actually being very accurate.
Effortful mental activity consumes high amounts of glucose. When we are actively involved in difficult reasoning or in tasks requiring self-control, our blood glucose levels drop.
When we are physically fatigued, we know it. When we are mentally fatigued, we don’t.
Unless we learn to recognize the clues.
When we are mentally fatigued, we become irritable, are easily distracted, blame others, and exercise less self-control.
Another result is a deterioration in the quality of our decision-making.
Good decision-making is a state that fluctuates, according to Psychologist Roy Baumeister. He says the best decision-makers are the ones who know when to NOT trust themselves.
The wisest don’t schedule endless back-to-back meetings because they know that decision fatigue is one of the cause of irrational trade-offs in decision making. They also know to schedule the activities requiring the greatest amounts of mental energy in the morning, and save the afternoons for simpler tasks with fewer consequences.
Our grocery stores know about decision fatigue.
As we go up and down the aisles, we are comparing prices and ingredients and making decisions. This is why they put all those snacks near the register to tempt us as we wait in line.
No matter how rational and intelligent we are, we cannot make decision after decision without paying a biological price.
The more choices we make throughout the day, the harder each one becomes. And when we’re tired enough, we do one of two things. One is to stop expending the energy required to think about the possible consequences and act impulsively instead. The other is the ultimate energy saver: do nothing.
If you’re not too mentally fatigued, please forward this article to a friend.