When it comes to explaining the how and why of sexual desire, there are few answers more reassuring than “because it’s in our DNA”, or “because we’re wired that way”. From why men love boobs to why both partners start wanting to scratch other sexual itches after seven years, a plausible-sounding biological explanation for our sexual predilections is always welcomed – apart from, of course, when it comes to BDSM.

Most general medical discourse about kink focuses on unpicking early childhood trauma, emotional disturbance or abuse (as experienced by the protagonist in Fifty Shades of Grey). Psychological arousal is not, however, just about physical stimulation, and physical reactions don’t confine themselves to psychologically comfortable circumstances. But when it comes to consensual kink, we could greatly benefit from more focus on the physical.

Put simply, there’s a science to spanking, to nipple torture, to candle waxing and to pretty much any other sex act you could name where prolonging the anticipation of touch or relief or safely manipulating blood flow causes the release of neurotransmitters – such as dopamine, adrenalin or serotonin – that result in a chemical high. It’s true that you have to be able to find that kind of physical stimulation arousing in order to be turned on, but if you do, having a person you find attractive putting you over their knee and spanking you in a way that encourages your body to release noradrenaline, adrenalin and dopamine in anticipation of the spank, and then opioids on point of contact is likely to be a pretty positive sexual experience.

And the research backs it up. Take some conducted by Meredith Chivers of Queen’s University, for example, which found that vaginal blood flow in women interested in BDSM increases when they watch kinky porn – at the same rate as it does for non-kinky women who watch vanilla porn. Conversely, blood flow does not increase when kinky women watch vanilla porn, implying that the brain has a part to play in controlling that blood flow, and that the brains of people who respond to kinky stimuli fire up the way those who respond to vanilla sex do. The pending fMRI scans of kinksters are expected to confirm what sexologists already hypothesise: there’s nothing neurologically or biologically dysfunctional about kink-related desire.

Most of us have demons and neuroses, swallowed frustrations and some of us act on them more than others and at different points in our lives. For a minority, BDSM may be a way those are expressed – as vanilla sex is for many others. But most of us lack the self-awareness necessary to pick apart the vagaries of our psychological motives and sexual peccadilloes. If you and your partner walk away from a sex act both satisfied and unscathed – or at least with no lasting emotional or physical bruises – perhaps that’s an outcome that needs no further probing.

Fifty Shades may certainly have opened up the general debate on kink, but social and legal prejudice still prevails. In the UK, December amendments to laws governing online porn fell disproportionately on kink acts. In the US, the First Amendment still does not apply to all sexual communications under the Communications Decency Act, if they are “patently offensive under local community standards” and cannot be proved to have “redeeming social value” by the author – particularly if they are kinky and non-heteronormative. And while the fifth edition of The Diagnostic and Statistical Manual of Mental Disorders may no longer consider sadomasochism or fetishism to be medical conditions, it still lists paraphilias such as sadomasochistic disorder and fetish disorder.

And the systemic prejudice against BDSM affects the funding of research that would help us better understand it. Off the record, American academics at major colleges have told me that their sex research projects remain on ice for months, sometimes years, and many American sexologists decamp to Canada where the liberal climate – and budgets – better facilitate research. Yet if the US National Institutes of Health won’t even fund, for example, research on the intersection of gender and health despite the massive current discussion around transgender identification, it’s unlikely to fund research on spanking and health.

If science was on the side of the kinky, how might that change the American mindset about what makes for good, clean and even godly sexual relations?

There’s almost certainly a methodology for exploring the science of kink – but if it threatens to challenge the sexual status quo, or inject some rationale into a debate about what kind of sex is acceptable, it’s a safe bet that it won’t be funded any time soon.