Many strangers give Dr William Struthers a quizzical look when he tells them what he does for a living. Some women even turn their eyes away in embarrassment. The American biopsychologist studies sexual arousal, but specifically what parts of the human brain light up, and what chemicals are unleashed, when people watch porn. Neuroscience has not only confirmed the old adage that 90 per cent of sex is in the mind - the brain being the control switch for arousal and orgasm - but its research results have become ammunition in the combat zone that is the pornography debate.

It's the pervasiveness of pornography today, says Struthers, that makes research like his especially relevant. Just 30 years ago, pornography was confined to seedy adult theatres, sex shops and copies of Penthouse tucked away behind newsagent counters. Back then, hardcore porn meant the graphic depiction of sexual intercourse in feature films and videos; softcore porn meant naked or topless pictures in Playboy. Now, hardcore means sadomasochism, gang bangs and body-punishing misogynistic sex, all available at the click of a mouse on the internet.

Illustration by Igor Morski/Illustrationroom.com.au.

Meanwhile, graphic sex on cable-television shows like Game of Thrones and True Blood, and music videos featuring gyrating, scantily clad pop sirens like Ke$ha and Nicki Minaj, have become the new softcore porn - leading music legend Joni Mitchell to lament that to be a woman in pop music today, you need to be a porn star.

Struthers says that Gen Y-ers (the under 30s) are in the midst of a second sexual revolution created in part by the explosion in pornography, leaving parents feeling ineffective and powerless. Filtering software on your home PC is not going to stop your teenage son from downloading pornography on his mobile, nor will it prevent your teenage daughter from posting topless photos of herself on dating sites. It's all part of a raunch culture in which body image and being sexy are paramount, in which casual hook-ups are replacing dating among the young, and the average age of first-time exposure to pornography is around 11.