In the great evolutionary skills race, our ancestors had to choose between being quick or dead, and the maximum speed with which their nerve cells could transmit information set a limit to how quickly they could deal with the world. Modern recording equipment shows that the fastest human motor neurones can transmit impulses at up to 120 metres a second – 432 kilometres an hour, which is about the cruising speed of a passenger jet. Young adults respond about 50 milliseconds faster when the period between the warning and the signal increases from 50 to 200 to 300 milliseconds. People aged between 65 and 75 need a further 50 to 100 milliseconds to reach their optimal preparation and, even when they are allowed this extra time, they do not gain as much as the young. The old gain more than the young from the additional advance information but, once again, they also need longer to make use of it.