Why making choices all day wears you out

By seven in the evening you've decided which emails to answer first, what to say to a client, whether to take the meeting, which supplier to use, what to have for lunch and how to word a delicate message to your team. Then someone asks what you want for dinner and you genuinely can't answer.

Many people recognise this feeling. It's often called decision fatigue.

What we know, and what we don't

The idea that our ability to make good decisions runs down over the day became popular after a 2011 study of judges in Israel. It found they were much more likely to grant parole early in the day and just after a food break than late in a session. Daniel Kahneman, the Nobel prize-winning psychologist, discussed the study in his book Thinking, Fast and Slow, and it was widely shared.

Since then, the picture has become less clear. Other researchers have pointed out that the order of cases wasn't random, and some of the wider research on willpower running out has been hard to repeat. So it's fair to say the science is still being argued over.

What most people agree on is simpler. Making lots of choices, especially ones that matter or involve other people, is tiring. When we're tired, we tend to fall back on whatever is easiest: putting the decision off, going with the default, or saying yes to avoid the effort of saying no.

Fast and slow

Kahneman described two kinds of thinking. One is fast, automatic and effortless, the kind that lets you drive a familiar route without thinking about it. The other is slow, careful and effortful, the kind you need to compare two job offers or write a difficult email.

The slow kind is the one that gets tired. You can't use it all day without paying for it. The aim, then, is to save it for the decisions that need it.

Let habits take the load

Wendy Wood, a psychologist at the University of Southern California, has studied habits for decades. In her research, people's diaries showed that about 43% of what they did each day was done almost automatically, usually in the same place and at the same time.

Habits feel boring, but they're a gift to a tired brain. Every decision you turn into a routine is one less decision to make. Habits form best when they're tied to a stable cue, such as a place, a time or something you already do.

Ways to make fewer decisions

Decide once. Make some choices in advance and stick to them. Same breakfast on weekdays. Gym on Mondays and Thursdays. Food shopping always on Saturday morning.

Use defaults. Set up regular payments, repeat orders and calendar templates so the choice is already made unless you change it.

Batch similar decisions. Answer all your quick-reply emails in one go. Approve expenses once a week rather than every time one arrives.

Move big decisions earlier. If you can, make important choices in the morning or after a break, not at the end of a long afternoon.

Narrow the options. Choosing between two good options is much easier than choosing from twelve. Cut the list first.

Know when "good enough" is good enough. Not every choice deserves research. For small decisions, pick the first option that does the job and move on.

One change for this week

Look at your evenings, when you're likely to be most worn out. Pick one recurring decision, such as what to eat, what to wear tomorrow or what to watch, and take it off the table. Plan the week's dinners on Sunday, lay out clothes the night before, or choose a series in advance. Then notice how much lighter the end of the day feels.