What happens to your reaction time if you are fatigued?

When a person is fatigued, their reaction time decreases significantly. This decline occurs because fatigue affects the central nervous system, leading to slower processing of information and diminished coordination. When driving, having a slower reaction time can impair one's ability to respond quickly to hazards or changing road conditions. A fatigued driver may take longer to recognize potential dangers, and their ability to react—through braking, steering, or other maneuvers—can be severely hampered.

In contrast, being well-rested typically allows for faster reaction times, as the mind and body are alert and ready to respond. Other options such as staying the same or improving do not reflect the reality of how fatigue impacts physical and cognitive functions. Additionally, while the idea of unpredictable reaction times might seem plausible, it is more accurate to state that fatigue consistently results in a decrease in reaction time rather than a fluctuating response.