Your reaction to a stimulus has multiple steps: 1) a sensor must respond to a particular stimulus 2) information of that stimulus gets sent to an integrating center 3) the integrating center determines a response 4) the integrating center sends a signal to an effector of the response In a biological system like yourself, these steps happen in the wetware of our cells and biochemical reactions, and these take time. The sum time of these steps we call the reaction time. For this assignment you and a friend will test human reaction times using a simple 30 cm or 12 inch ruler. Procedure 1) Have your subject extend their dominant hand off the edge of a table or counter with their thumb and index finger extended with a narrow gap between them. (Having the forearm against a table or counter prevents the catcher from moving their arm to track and catch the dropped ruler.) 2) Dangle a 30 centimeter (12-inch) ruler from the 30 cm mark (i.e., the top of the ruler), positioning the 0 mark between your subject's thumb and index finger. 3) Instruct your subject to catch the ruler as fast as possible, once they SEE it released. 4) Record the centimeter (or inch) measurement where your subject caught the ruler. 5) Repeat this procedure three more times, for a total of four measurements. 6) Convert your measured drop distances to meters, and then use the kinematic equation to calculate the drop times. Then determine the mean drop time, i.e., reaction time. d=gt t = 2d g 2d g drop distance (m) Seconds Mean time: