Late last year, Christian Joyal and his colleagues published a paper in the Journal of Sexual Medicine titled, What Exactly is an Unusual Sexual Fantasy? Over 1,500 women and men rated their interest in 55 sexual fantasies ranging from sex in a public place, to tying up a sexual partner, to watching two men make love. Topping the list were fantasies about oral sex, sex in romantic locations or unusual places, and sex with someone other than one’s spouse.

But not far below were fantasies about being dominated sexually (present in 65% of women and 53% of men), dominating someone sexually (47% of women, 60% of men), and being tied up for sexual pleasure (52% of women, 46% of men).

These results will come as no surprise to anyone following the remarkable sales of Fifty Shades of Grey and its sequels. Whatever anyone says about the books and upcoming movie, they have started a conversation about the themes of bondage and discipline, dominance and submission, sadism and masochism (BDSM), that permeate many people’s sexuality.

My research lab studies the effects of consensual BDSM activities on its practitioners. We collect data in the field, attending events hosted by BDSM organisations and recruiting participants who are willing to fill out surveys, provide saliva samples, and take cognitive tests before and after their BDSM scenes. Our goal is to understand the physiological and psychological effects of these BDSM activities and whether these effects differ for bottoms (the people who are bound, receiving stimulation, and/or following orders) and tops (the people providing the stimulation, orders, or structure).

Across our studies, from before to after their scenes, both bottoms and tops show an increase in relationship closeness, decreases in psychological stress, and evidence of altered states of consciousness. Bottoms and tops differed, however, in the type of altered state they appear to enter.

Bottoms show evidence of an altered state associated with a temporary impairment of the brain’s executive function capability accompanied by feelings of floating, peacefulness, time distortion, and living in the here and now. This altered state, often referred to as “subspace” within the BDSM community, aligns with psychologist Arne Dietrich’s “transient hypofrontality hypothesis”, an explanation for a diverse set of altered states from runner’s high to daydreaming to hypnosis.

Tops, in contrast, appear to enter an altered state aligned with psychologist Mihaly Csikszentmihalyi’s concept of flow, a highly pleasurable mental state associated with focused attention, a loss of self-consciousness, and optimal performance. As with subspace, the BDSM community has a term for this altered state: “topspace”.

All of these effects — reductions in stress, increases in intimacy, and the facilitation of pleasurable altered states of consciousness — point to the positive impact that BDSM activities can have on relationships. This positive impact is predicated, however, on the presence of consent.

In her paper Consent vs. Coercion: BDSM Interactions Highlight a Fine but Immutable Line, Dulcinea Pitagora identifies consent as the critical element that distinguishes BDSM from abuse. As Pitagora notes, the BDSM community has developed a number of mechanisms that reinforce consent and protect the wellbeing of participants. These include safewords, pre-defined words that signal that scene activities must slow down or change, or that the scene must end immediately, and aftercare, gentle contact and quiet communication between the top and bottom after the end of the main scene activities. Aftercare often comprises a significant portion of scene time. In our study of altered states, for example, participants spent a quarter of their total scene time in aftercare.

How does this play out in long-term relationships? A doctoral dissertation by Bert Cutler titled Partner Selection, Power Dynamics, and Sexual Bargaining in Self-Defined BDSM Couples provides some answers. Cutler conducted extensive interviews with 33 individuals in long-term BDSM relationships, and Cutler’s analysis of these relationships identifies some important principles. First, sexual compatibility does not require a couple to have identical kinks. Rather, each person needs to find palatable what turns his or her partner on. Thus, a person with a foot fetish would be incompatible with a partner who could not tolerate having his feet touched. But a person who liked to be spanked could develop a satisfying sex life with a partner willing to spank him, even if spanking was not a particular turn on for the partner.

Second, what makes this arrangement work is sexual gift-giving, the willingness of each person to provide for their partner the acts that turn their partner on. Dan Savage, author of the popular sex advice column Savage Love calls this being GGG: good, giving, and game.

Third, over the long term, couples begin to internalise the excitement that these acts provided for their partners, eventually finding intrinsic enjoyment in the acts themselves.

This is good news for the solid majority of people whose sexual interests expand beyond the heterosexual missionary position. We do not need to find a sexual soulmate. Sexual fulfilment does not require a partner whose kinks correspond perfectly to our own. Rather, fulfilment requires a willingness to disclose, a willingness to hear disclosure, and a willingness to provide to our partner what he or she needs to be fulfilled.