NATURE OF EXERCISE:
This is the simplest of all the exercises. It's a pure measure of your reaction time, i.e., how fast you can respond to random visual stimuli.

RELEVANCE TO EVERYDAY LIFE:
Physical reactions use very little of the cognitive process. Accordingly, the average reaction time for middle-aged individuals is in the 250 - 300 millisecond range for visual stimuli (or far shorter than the full one second it takes to form a thought; one millisecond equals one-thousandth of a second). Professional athletes typically have reaction times of less than 200 milliseconds. And, it's a good thing we can react so quickly. If not, our streets would resemble a Demolition Derby. Fortunately, reaction times can be significantly improved with training. A one-tenth of a second improvement translates into an extra 8.8 feet of stopping distance as you're zipping down the highway at 60 mph.

INSTRUCTIONS:
A vertical display of lights, similar to a traffic signal, is presented. When the light changes from red to green, press the DOWN ARROW key on your keyboard as quickly as possible, then release it and get ready for the next trial. If you press the key before the light turns green, this counts as an error and serves to reduce your score. You must respond correctly 20 times to complete the exercise.