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    Reaction time is defined as the amount of time it takes to respond to a stimulus, which can be any event that comes before a response. The human brain is immensely complex, and the typical time it takes for a physical response to a stimulus is around 160 to 190 milliseconds — or a little less than 0.2 seconds. That’s around the same time it takes to blink.

    While our physical reactions can happen in a blink of an eye, behind the scenes our brain is working through a series of processes. For example, before responding to a baseball being thrown by a pitcher, a catcher’s brain must recognize the ball, decide to respond, then send a message down the spinal cord to their hands and fingers.

    A person’s reaction time can vary based on a variety of factors. Some factors are outside of our control — such as age, left or right-handedness, and whether the stimulus is visual or auditory. Other factors that affect reaction times are within our control, like our level of physical fitness, the presence of distractions, and how much fatigue we’re experiencing.

    Can a Lack of Sleep Affect Reaction Time?

    Getting sufficient sleep is an essential part of both physical and mental health. Guidelines from the National Sleep Foundation indicate that most adults need between seven and nine hours of sleep per night. Unfortunately, being underslept is fairly common and data from the Centers for Disease Control (CDC) suggests almost one-third of Americans get less than six hours of sleep each night.

    Reaction times increase as a person accumulates sleep debt. This means that the more sleep a person loses, the longer it takes for them to react to a stimulus. In one study, research subjects were allowed to sleep for five hours per night for a week. Over the course of the week, participants’ reaction times steadily increased as they accumulated sleep debt and felt increasingly sleepy.

    There are several hypotheses that attempt to explain the reason for increased reaction times after sleep deprivation. One hypothesis asserts that sleep loss increases reaction time due to the body’s simultaneous and competing needs. When we’re underslept, our body is experiencing a need for sleep, a need to stay awake, and a need to perform tasks. These competing drives interfere with our attention from moment to moment, leading to cognitive impairment and an increased reaction time.

    The Dangers of an Increased Reaction Time

    Reaction times are important in a multitude of professions and activities. Increased reaction times can affect the performance of athletes, as well as the safety and productivity of shift workers, medical professionals, students, pilots, and anyone else whose work requires sustained attention and quick reflexes.

    Increased reaction times are particularly dangerous when a person gets behind the wheel of a car. The National Highway Traffic Safety Administration estimates that up to 6,000 fatal crashes each year may be due to drowsy drivers. Driving while underslept can make it more difficult to react quickly to changing road conditions and has been linked to dangerous practices like lane drifting.

    How to Test Your Reaction Time

    There are several ways to test your reaction time at home. While these methods shouldn’t be used to decide if you’re too drowsy to drive or do other tasks, they can be a fun way to test your reaction time under different conditions.

    The Ruler Test

    This simple reaction time test allows you to see how long it takes you to catch a falling ruler. To start, have a friend hold a ruler on the highest measurement. Place your open thumb and forefinger slightly below the ruler, ready to catch it when the ruler falls. Then, have your friend drop the ruler while you catch it between your thumb and forefinger as quickly as possible.

    Record the measurement where you caught the ruler. The lower the number, the quicker the ruler was caught and the higher your reaction time. For fun, switch positions with your friend and let them try, then compare your results. You can also compare your reaction time during different conditions, like with or without background noise.

      The Psychomotor Vigilance Test

      The psychomotor vigilance test (PVT) measures how long it takes to respond to a visual stimulus. Images are shown on an otherwise blank screen at random times and participants are asked to touch a button when they see the image. While this test can be difficult to recreate on your own, there are several computer and smartphone-based applications that allow you to test your reaction time under different conditions.

      Improving Your Reaction Time

      Many people want to improve their reaction times to be a safer driver, more productive at work, or quicker at responding in conversations. Others, like new parents, shift workers, and emergency responders, need to maintain quick reaction times under conditions that often require them to miss sleep. While these tips can’t replace a good night’s rest, there are several ways that people can improve their reaction time, both in general and when they’re underslept.

      • Improve hand-eye coordination: Training in hand-eye coordination can improve reaction times and the improvements may stick around long after the training ends. Try picking a sport or activity that involves hand-eye coordination and practicing on a regular basis for the best results.
      • Be aware of alcohol and caffeine: Alcohol and caffeine have opposite effects on reaction times. Alcohol slows reaction times, even at low levels before a person feels or acts intoxicated. Caffeine, on the other hand, can improve reaction times. While caffeine may help increase reaction time temporarily, don’t forget that it can also interfere with sleep if used too close to bedtime.
      • Try meditation or deep breathing: Research suggests that meditation can improve reaction times, even in people who are sleep deprived. Slow, deep breathing has shown similar benefits. Try practicing deep breathing or meditation before activities that require quick reaction times.
      • Improve your sleep: Since sleep loss can have such dramatic effects on reaction times, make sure you’re getting consistent, quality rest. If you’re experiencing sleep issues that are preventing you from getting the rest you need, try a few of our tips for improving your sleep.

      Improving Your Sleep

      Improving your sleep hygiene is a great first step to feeling more rested and improving your reaction time. Sleep hygiene means incorporating practices that promote better sleep, while reducing practices that are making sleep more challenging. Here are a few tips for improving your sleep hygiene.

      • Get outside and be active: Getting enough daylight and physical activity are two vital steps in improving sleep hygiene. Both sunlight and exercise help to sync the sleep-wake cycle, an important circadian rhythm.
      • Be consistent: Establish a nighttime routine and keep it consistent. Try creating an order for your evening, like showering first, then brushing your teeth, then putting on your pajamas. Following the same routine each night can help your mind and body wind down and know that it’s time to sleep.
      • Improve your sleep environment: Choose a reasonable amount of time before bed (maybe 30-90 minutes) to turn off or silence all distractions, especially electronics like your TV and cell phone. Find a calming activity to do instead, like stretching, reading, or relaxation exercises.
      • Understand the role of diet: Drinking coffee or eating a large meal too late in the evening can disrupt sleep. Alcohol may make it easier to fall asleep initially, but it can disrupt sleep later in the night. Try to limit alcohol and caffeine, especially in the evening.
      • Talk to your doctor: If you have persistent difficulties getting enough sleep, it’s important to talk to a medical professional. Doctors, sleep specialists, and even mental health counselors are trained to help find and treat issues that affect your sleep.
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