This activity is designed to let learners measure their reaction time or response time to something they see. Learners work in pairs and measure the speed it takes them to catch a ruler dropped by their partner. Learners use a table to convert the distance measured on the ruler to reaction time. Learners can calculate more reaction time using the algebraic formulas provided. Learners can expand on this activity by comparing the speed of an entire group, boys vs. girls, kids vs. parents, etc. This activity is one of several activities featured on this webpage related to human reflexes.