A penalty kick that illustrates reaction time
During Euro 2020, Swiss goalkeeper Yann Sommer faced one of the most talented strikers in the world — Kylian Mbappe — in a decisive penalty shootout. In a matter of milliseconds, Sommer had to process the visual cues from Mbappe's run-up, decide which direction to dive, and execute a precise motor response. He saved the penalty. This remarkable moment provides a perfect real-world illustration of what reaction time actually involves and why it matters so much in sport and everyday life.
But what exactly happens in the brain and body during those critical milliseconds? Reaction time is far more than a simple reflex — it is a complex chain of neurological events that can be trained, optimized, and measured.
The three neurological pathways
Reaction time can be broken down into three distinct neurological stages, each of which contributes to the total time elapsed between a stimulus and the corresponding response.
1. The sensory pathway
The process begins when a stimulus — such as a ball leaving a striker's foot — is detected by the sensory organs. In the case of visual stimuli, light enters the eye and is converted into electrical signals by the retina. These signals travel via the optic nerve to the visual cortex, located at the back of the brain. Here, the raw visual data is processed into meaningful information: the direction of the ball, its speed, and its trajectory.
2. Cognitive processing
Once the sensory information reaches the brain, it must be interpreted and a decision must be made. This stage takes place primarily in the cerebrum, the largest part of the brain. The cerebrum evaluates the incoming information, compares it against stored knowledge and previous experiences, and selects the appropriate response. In a goalkeeper's case, this means deciding whether to dive left, right, or stay in the center.
This cognitive processing stage is often the longest component of reaction time, especially when multiple response options are available. As the complexity of the decision increases, so does the time required to process it.
3. The motor pathway
After a decision has been made, the brain sends electrical signals through the motor cortex and down the spinal cord to the relevant muscles. These signals instruct the muscles to contract in the precise sequence needed to execute the chosen movement — for example, pushing off with the legs and extending the arms to reach the ball.
In addition to these three primary pathways, the cerebellum plays a crucial role in fine-tuning the motor response. The cerebellum acts as a quality control center, making real-time adjustments to ensure that the movement is smooth, coordinated, and accurate.
Hick's Law: the cost of choice
"Every time the amount of stimuli-response choices doubled, reaction time increased by 150 milliseconds." — Schmidt & Lee
This principle, known as Hick's Law, is one of the most important findings in reaction time research. It demonstrates that reaction time is not fixed — it increases logarithmically with the number of available response options. A simple reaction (one stimulus, one response) is far faster than a choice reaction (multiple stimuli, multiple possible responses).
This has profound implications for sport. A goalkeeper facing a penalty has at least three major options (dive left, dive right, stay center), and within each option there are variations in height and timing. Every additional option adds processing time. This is why many athletes try to reduce the number of choices they must make in the moment by studying opponents' tendencies beforehand.
Factors that influence reaction time
Reaction time is not a fixed trait. It varies significantly between individuals and even within the same individual depending on a range of factors:
Age: Reaction time improves throughout childhood, peaks in early adulthood (typically between ages 20 and 30), and then gradually declines with age. This decline is associated with slower neural conduction and reduced processing speed in the brain.
Sex: Research consistently shows small but statistically significant differences in reaction time between males and females, with males tending to have slightly faster simple reaction times. However, these differences diminish or disappear for more complex cognitive tasks.
Practice: One of the most powerful factors. Repeated practice of a specific task creates more efficient neural pathways, reducing reaction time significantly. This is why elite athletes can react to stimuli far faster than untrained individuals in sport-specific contexts.
Fatigue: Both physical and mental fatigue slow reaction time. Fatigued muscles respond more slowly, and a tired brain processes information less efficiently. This is particularly relevant in the later stages of a match or competition.
Exercise: Moderate exercise has been shown to temporarily improve reaction time by increasing arousal and blood flow to the brain. However, exhaustive exercise can have the opposite effect.
Intelligence: General cognitive ability is positively correlated with reaction time, particularly for complex choice-reaction tasks that require significant cognitive processing.
Task complexity: As Hick's Law demonstrates, the more complex the task and the more response options available, the longer the reaction time.
Training reaction time with Aristotle
Understanding the neurological basis of reaction time opens the door to targeted training. By systematically challenging the sensory, cognitive, and motor pathways involved in reaction time, it is possible to achieve meaningful improvements. Aristotle's platform offers exercises that specifically target each of these pathways, allowing therapists and coaches to design training programs that address the exact demands their clients face — whether that is a patient relearning to respond to environmental hazards or an athlete sharpening their on-field reactions.