GAME: Test Your Reaction Time

You need to act quickly to avoid hitting animals, vehicles, or other objects on the track, or on the road when you drive to and from work. A computer game, Think Fast!, simulates the driving experience.

The game runs for 5 minutes. Some users get bored after 2-3 minutes. That's expected. Try to keep going. It's a challenge to stay alert in boring situations, such as driving at night on a straight track or highway.

Test your skill today, and come back another day or another time of day to see how your alertness varies. Your level of alertness or fatigue, recent use of caffeine or alcohol, and other factors may alter game results from one time to the next—just as they do your driving performance.

Remember: reaction time is only one indicator of your performance. Accuracy also is critical.

Play the game now.

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Sleep Loss Clouds Judgment

Most adults need 7-8 hours' sleep per day, ideally at night, for optimal alertness. Railroaders often may not be able to get that much sleep in their longest period of sleep. They can boost alertness with naps, however. People who get less sleep than they need often complain of feeling wiped out.

After a day or two of not getting enough sleep, most people recognize that they feel cranky, foggy, and clumsy. They may have trouble with concentration and memory. Their reaction time slows.

If people miss sleep several days in a row, these problems typically increase. Sleepy people often do not realize how fatigued they are, and how poorly they perform at work or behind the wheel. Sleep deprivation undermines the ability to pay attention, retain information and process it, make decisions, and manage other aspects of complex thinking.

Sleep Deprivation and Judgment (01:01)
Christopher Landrigan, MD, MPH, of Harvard, tells how sleep loss keeps you from realizing how sleepy you are.

Drowsy or Drunk?

Both States Slow Reaction Time and Judgment

After 16 hours of wakefulness, performance slips.

People who took a driving test after 17-19 hours awake performed as badly as or worse than people with a blood-alcohol level of 0.05 percent, the legal cut-off for being considered drunk in most western European countries. At this level of impairment, an individual's reaction time is about 50 percent slower than that of a well-rested person.

People who took a driving test after staying awake for 24 hours performed as poorly as people with a blood-alcohol level of 0.10 percent. This blood-alcohol level is only slightly above 0.08 percent, the current legal limit for alcohol intoxication in the United States. 1

Tired drivers, like those who are drunk, lose not only their ability to drive safely, but also to recognize how impaired they are.2

Sleep and Memory (01:10)
Robert Stickgold, PhD, of Harvard, tells how sleep helps you learn facts and remember them.


  1. Williamson A, Feyer A. Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occup Environ Med 2000 Oct;57(10):649-55.
  2. Cohen DA, Wang W, Wyatt JK, Kronauer RE, Dijk DJ, Czeisler CA, Klerman, EB. Uncovering residual effects of chronic sleep loss on human performance. Sci Transl Med 2010;2(14):14ra3.

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This content was last reviewed on June 6, 2012