At a stoplight, the instant it turns green, drivers react—some faster than others. But how quickly does your brain process the change and tell your foot to hit the gas? In this experiment, we explore visual reaction time—the interval between seeing a stimulus and responding with movement. A flash of light appears, and your brain races to process it. Your muscles spring into action, but how fast?
Test your visual-motor response and see how quickly you react!
Humans have been fascinated by reaction time for centuries. Early scientists pictured the body as a hydraulic system; we now know our responses are powered by electrical signals travelling through neurons. With the Human SpikerBox and Reaction Timer, we can time visual reaction precisely. Whether catching a falling object or responding to a light change, we can measure and analyze the delay between stimulus and movement.
Plug the Human SpikerBox into your device via USB, then connect the Reaction Timer with the orange cable. Set the Reaction Timer’s switches to LED On, Sound Off and Random Off.
Attach the two red clips to stickers on the subject’s forearm and the black clip to a sticker on the back of the hand. If you have more participants, connect player 2 to channel 2 so they can race each other each trial!
Connect the electrode cable to the SpikerBox, confirm the battery is installed correctly, open SpikeRecorder, and power on the SpikerBox.
This task works best with two or three people, so grab a partner. One will be the experimenter, the others the subject. You’re recording a simple reaction time—how fast can you respond with no distractions?
Subjects focus on the Reaction Timer. Their goal is to flex their muscle as fast as possible when they see the green LED light up. (For this experiment we use only the green button.)
Start recording in SpikeRecorder. The experimenter presses the button 10 times at random intervals—don’t go too fast and keep the timing sneaky. Cover your hand so subjects react only to the light.
After the run, measure each RT in SpikeRecorder and calculate an average for every participant. Who’s fastest?
Compare results across the class. Do you see differences between dominant and non-dominant arms? How about gamers versus non-gamers?
Draw the path from your eye to your forearm muscle: eye, brain, spinal cord, motor neuron, muscle. Mark where the green light starts the clock and where your EMG electrodes stop it.
The sensing–processing–responding loop, timed end to end.
MS-LS1-8 Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories.
HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.
2 Developing and Using Models
Draw the path from your eye to your forearm muscle and mark where the clock starts and stops.
3 Planning and Carrying Out Investigations
Time ten reactions to a light with the Reaction Timer and forearm EMG.
4 Analyzing and Interpreting Data
Compare reaction times between people, arms, and gamers and non-gamers.
5 Using Mathematics and Computational Thinking
Measure each reaction time in SpikeRecorder and average them.
Cause and Effect
Practice (gaming) and arm dominance may change reaction time.
Systems and System Models
Timing the full loop.
LS1.D Information Processing
Receptor → brain → muscle information flow.
LS1.A Structure and Function
System organization.
Performance expectations, crosscutting concepts and core ideas from Hands-On Neuroscience Curriculum Overview, Unit 2, module 2.3, whose core lab this is. The practices are the ones this page asks students to do.
