Frontline Psych With Doc Bender: Why Cognitive Fatigue Matters

U.S. Marine Corps photo by Lance Cpl. Andrea Dickerson

U.S. Marine Corps file photo by Lance Cpl. Andrea Dickerson

Have you ever been a turret gunner and had trouble staying vigilant on a long convoy? Ever been at the range all day and your shooting actually got worse by the end of the day? Have you found yourself stuck in a long meeting at work and noticed you stopped paying attention? If so, then you’re already familiar with cognitive fatigue (sometimes called mental fatigue). It’s defined as changes in the brain after long periods of mental activity that cause a decrease in mental performance. In other words, your brain gets tired after thinking for a long time and starts to slow down.

This cognitive fatigue is different than sleep deprivation or being physically tired (although people with cognitive fatigue report feeling physically drained and do worse on physical performance tests). Cognitive fatigue happens to everyone, even when they are well rested, mentally fit and in an ideal environment. However, recognizing when you’re feeling fatigue and taking steps to minimize its effects are important.

The Science Behind Mental Fatigue

Most people can only pay close attention to something for about 40 minutes. After this period, things start to happen to your brain. For example, the anterior cingulate cortex starts to slow down, partially because it’s getting less dopamine, a brain chemical that activates it. This cortex is responsible for paying attention, planning activities and detecting errors. The striatum also slows down. This part of your brain plans and prevents physical activity (prevents you from pulling the trigger when you shouldn’t pull the trigger). Additionally, your brainwaves are altered. Brainwaves are the electrical activity the brain produces as a result of millions of brain cells constantly firing. All these things happen regardless of how motivated or interested you are in a subject.

Some of the effects of cognitive fatigue include:

  • Impaired coordination
  • Difficulty focusing
  • Memory problems
  • Decreased ability to spot errors
  • Trouble controlling impulses
  • Difficulty adapting to new situations
  • Trouble performing jobs that require a lot of physical stamina

Often, performance of simple tasks generally doesn’t suffer. (Have you ever cleaned your weapon when you’ve been dead tired and couldn’t think? You probably did a decent job.) On the other hand, mental fatigue can be dangerous, especially when performing tasks that require constant concentration, such as driving a Humvee for a long distance.

How to Combat Cognitive Fatigue

So, what does all this mean for service members and other professionals? It means that you should take short breaks throughout the day to allow you to refocus and stave off cognitive fatigue. You simply want to allow for downtime. You should also switch tasks if possible every hour or so or when you’re feeling burnt out. And, for those planning missions or meetings, it’s important to remember that cognitive decline is inevitable, adversely affects performance and should be factored into mission planning.

Story by Dr. James Bender
Defense Centers of Excellence

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