Does talking on a cell phone make people react slower when driving? Sixty volunteers agree to have their reaction times tested in a driving simulator. Thirty of the drivers were randomly assigned to talk on the phone during the simulation, while the other drivers do not talk on the phone. During the simulation, a surprise event occurred which required the subject must to step on the brake. The time it took them to react is recorded. The mean response time of those talking on the phone was 4.3 seconds. The mean response time of those not talking on a cell phone was 2.9 seconds.