text: Reaction time is the measure of how quickly an organism can respond to a particular stimulus. When your spending time at your phone and finally look up to see you're about to get into an accident it would already be too late. Reaction times with no activity were between one and two seconds. Reaction times while using a cellphone were at least three to four seconds. On top of that, drivers were more likely to miss the flashing light altogether when using a cellphone. Cellphones effects the nervous system when a person is driving.