<P> Erections are common for children and infants, and even occur before birth . After reaching puberty, erections occur much more frequently . The penile plethysmograph which measures erections has been used by some governments and courts of law to measure sexual orientation . An unusual aversion to the erect penis is sometimes referred to as phallophobia . </P> <P> Spontaneous erection, also known as involuntary, random or unwanted erection, is commonplace and a normal part of male physiology . Socially, such erections can be embarrassing if they happen in public or when undesired . Erections can occur spontaneously at any time of day, and if clothed may cause a bulge which (if required) can be disguised or hidden by wearing close - fitting underwear, a long shirt, or baggier clothes . </P> <Table> <Tr> <Td> </Td> <Td> Wikimedia Commons has media related to Erect human penis . </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> Wikimedia Commons has media related to Erect human penis . </Td> </Tr>

What is the physiological reason for erectile dysfunction