In many mammalian males the speed of erection is remarkably fast. A period of three or four seconds from a fully flaccid state to full erection is commonplace and in many species the time is even less than this. Kinsey has remarked that "stallions, bulls, rams, rats, guinea pigs, porcupines, cats, dogs, apes, and males of other species may come to full erection almost instantaneously upon contact with a sexual object." As we may expect, the youngest men get the speediest erections in humans.