A liberal professor of psychology who studied in the late 1970s will see [pedophilia] very differently from someone working in child protection, or with convicted sex offenders. There is, astonishingly, not even a full academic consensus on whether consensual paedophilic relations necessarily cause harm. So what, then, do we know? A paedophile is someone who has a primary or exclusive sexual interest in prepubescent children. But not all paedophiles are child molesters, and vice versa: by no means every paedophile acts on his impulses, and many people who sexually abuse children are not exclusively or primarily sexually attracted to them. In fact, true" paedophiles are estimated by some experts to account for only 20% of sexual abusers. Nor are paedophiles necessarily violent: no firm links have so far been established between paedophilia and aggressive or psychotic symptoms. Psychologist Glenn Wilson, co-author of The Child-Lovers: a Study of Pedophiles in Society, argues that "The majority of paedophiles, however socially inappropriate, seem to be gentle and rational." Legal definitions of paedophilia, needless to say, have no truck with such niceties, focusing on the offence, not the offender. The Sex Offenders Act 1997 defined paedophilia as a sexual relationship between an adult over 18 and a child below 16. There is much more we don't know, including how many paedophiles there are: 1-2% of men is a widely accepted figure. Even less is known about female paedophiles, thought to be responsible for maybe 5% of abuse against pre-pubescent children in the UK.