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.
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.
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.
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.
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 (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.
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.
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.