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Getting in "sync" with a partner may not be a euphemism.

“Don’t knock masturbation, it’s sex with someone you love,” quipped Woody Allen. It’s a funny line, but it’s not really true. Not that there’s nothing wrong with masturbation—it’s healthy for a whole bunch of reasons—but it’s not that much like sex with another human being. Certainly not so much that it’s a full substitute for it. If you think purely in terms of orgasm as a goal, this is a puzzle. But, it’s a puzzle we are closer to solving.

“The pleasure is momentary, the position ridiculous, and the expense damnable”1

A recent paper2 found, with a large (N = 52,588) U.S. sample, that homosexual couples are (unsurprisingly) better at generating orgasms in one another than heterosexual partners are—especially with women. Heterosexual men, gay men, bisexual men, and lesbians reported having orgasms most reliably (95%, 89%, 88%, and 86% of the time, respectively) whereas bi and straight women reported the least (66% and 65% respectively).

I’ve discussed at length some possible reasons for this orgasm gap before.3 Long story short—in a species like ours where the bulk of the sexual selection is done by females, one should expect said females to be relatively picky about the selection mechanisms. To put this pickiness bluntly, 80% of your ancestors are female, 40% of them are male.4 This has had dramatic effects on us. Female choice mechanisms drive adaptations in all primate species, and ours is no exception.

But the issue of orgasm reliability goes even deeper than that. Both sexes can far more reliably generate orgasms on their own (or with help from the vibrator manufacturers) so why risk rejection and disease, while investing time and money, all for a momentary pleasure? Are we just mindless puppets pulled by genetic strings?

An orgasm is an orgasm, isn’t it? Well, no. For one thing—the pleasure of sex is not always that momentary. The research on orgasm, coupled with statements like “the average time to complete intercourse is two minutes,”5 would make an alien anthropologist studying our species think that for humans (allegedly homo sapiens) to pursue such pleasures would not simply be a bit irrational, it would be actively insane. Why haven’t sex researchers made more of this until recently?

There’s a range of brain activity that we do not study in much detail because we are used to studying one person at a time. “Fill in this questionnaire please”; “Press the button when you see the gorilla”; “Follow the dot on the screen while we measure your brain waves.” And there is absolutely nothing wrong with this sort of research. But a lot of the most interesting things that humans do are in sync. Dance, conversation, song, and shared meditative states (like prayer) are good examples. Mothers and babies are in sync6. If you videotape a mother and baby interacting and slow video down, they appear to be performing a synchronous dance. Depressed mothers do not show this interaction, only happy ones.

A recent paper by Adam Safron7 advanced the fascinating hypothesis that one aspect of orgasm, that has been insufficiently studied, is the set of features that follow from shared rhythm. As we say, “getting in sync.” This may not be mere analogy.

Given the fact that sex is fun, one might expect the enjoyment to reinforce behavior and push us to repeat that fun with those we share it with. Diana Fleischman8 recently wrote a paper exploring this idea and the attendant notion that we can (and should) shape our partners (and they us).

(Sound relationship advice about mutual reinforcement.)

One reaction from people I talk to about this is that the idea seems so obvious that they are baffled that more scientists haven’t explored it. I suspect that later generations will look back with similar astonishment that this possibility—that the reward of orgasm helps to cement bonds with partners—was not even considered by proponents of the dominant theory of female orgasm in the field. But, that’s ideology for you. As the old saying goes: assumptions are those things that you don’t know that you are making.

However, reinforcement alone cannot be the whole story (Not that Diana Fleischman would argue that it was). The concept of “bed death” (and not just the “Lesbian Bed Death” that Pepper Schwartz described in the 1980s) is very real.9

Sex is not just habitual: We need to hit a sweet spot between novelty and routine so that we do not get staid and boring with our sexual partners. This zone is what Csikszentmihalyi called “flow.”10 That is, sufficiently novel to hold our attention, yet sufficiently within our capacities not to overwhelm us. A state of flow is characterised by six things:

  1. Focussed concentration
  2. Merging of action and awareness
  3. Loss of self-consciousness
  4. Feeling of personal effectiveness
  5. Altering of sense of subjective time passing
  6. Sense of intrinsic reward

Well, that sounds like a pretty good rundown of what distinguishes good sexual encounters. The sort where we would (both, one hopes) like a second helping. And the converse of any of these criteria could easily be exactly the sort of thing that sends people to sex therapists.

For those who take more than two minutes in having sex (and let me step out of my scientific detachment here for a moment, and express the hope that this is most of us) there is the regular sensation of losing all sense of time, being focused, merging action and awareness and so on. That is how it feels to have good sex (what we call the phenomenology of the experience) but are there reasons to think that this experience is grounded in neurology?

A Little More Conversation and a Little More Action, Please…

Yes, indeed there are. I mentioned above that a lot of the most rewarding human experiences are shared ones. It is no accident that singing, dancing, and talking are much more fun with two (or more). One has to be careful with the prefix “neuro”, because (along with the buzzwords “Nano", "Paradigm", "Organic", "Green" or "Quantum") this can signal that someone is about to pull a fast one. Or try to sell you snake oil. So, let’s proceed carefully and not pretend to know more than we do.

What do we know? We know that Darwin11 noted that males across species get female interest through rhythmic displays, something confirmed by modern studies12.

But that is just the first suggestive step. Females may do the lion’s share of selecting in our species, but males do quite a bit too, and both sexes (or both members of the same sex) have to both control their own bodies and respond to the cues being sent to them by their partner. Attentiveness and conscientiousness in the bedroom may signal qualities needed for mutual child rearing13 and conscientious consideration to partner needs is certainly a quality significantly predicting orgasmic response in our participants.14 But what happens inside the brain?

Rhythm Is Gonna Get Ya

Robert King
Source: Robert King

The following is admittedly speculative—but you need to speculate to accumulate. And one of the things we want to do in science is generate fields of inquiry that we can explore. Here is something worth exploring: Brains are electrochemical engines and they oscillate at measurable frequencies. When we put one of those funny hats with electrodes in it on you in the lab, it’s those frequencies that we are measuring across the surface of the brain.

These oscillations are generated by small parties of neurons firing (one is tempted to say “dancing”) together. Neurons are more likely to dance if those near them are doing so: In technical terms, they generate action potentials more readily if their inputs arrive closely in time, meaning that they synchronise and send the signal onwards.15

Things get a little technical here and, also philosophically tricky. “What is consciousness?” is a philosophical question that has not been answered to everyone’s satisfaction. Some think that there is a "hard" problem that will always be beyond science16 while others think that there are lots of (Ho! Ho!) “easy” problems, and once we have solved those—we will know all there is to know about consciousness. Well, one of the so-called “easy” problems is the “binding problem.” Namely, “how is it that the different inputs from different perceptual streams give us the unified experiences that we have?”17 In order to illustrate this, let me do what cognitive psychologists love to do with systems and mess with it for a few minutes:

Wasn’t that cool? The McGurk illusion is a lovely illustration of the way that normally our perceptions (in this case auditory and visual) bind together seamlessly18. Except when they don’t. One proposed solution to the binding problem is that separate brain systems can get in synch with one another—oscillating at the same frequency—giving rise to the rich and integrated phenomenology of the world.19

“Biggie Biggie Biggie, can’t you see…Sometimes your words just hypnotize me”

How can we improve this “getting in synch”? The answer is a phenomenon called “entrainment”.20 Have you ever run a wet finger round glass, to the amusement (or annoyance) of the other diners? If you get the friction right, the glass starts to sing—it is oscillating at a particular frequency. Do this right and other glasses in the vicinity will also sing, or even break. This is very much like the phenomenon of entrainment—where the neurons start to “sing” to one another in synchronous delight. We do not know if this happens during sex—but it’s certainly worth investigating. We have clues to suggest that entrainment enhances musical enjoyment21 and positive feedback between pleasure and attention could well explain why there is much in common between being lost in music and lost in a partner.

(Entrainment in metronomes)

A large amount of what the brain does is stopping other brain regions doing their thing. The late great AI researcher Marvin Minsky22 described the brain as a “bunch of tiny robots trying to fool each other” and that is a pretty good way to think of it. What this means is that the activation of some areas inhibit or disinhibit other regions. When we experience loss of control in dance, music or sex we are not really losing control so much as having the experience of an unusual part of us temporarily in the driving seat. Is this more than a useful way of talking? We can make some specific predictions here: A loss of self would be expected to occur with deactivation of frontal midline structures during sex23 in a similar way to what we have observed during trance-like states. This would be tough to study—but we can hope that brain scanning techniques continue to improve over the next few years.


Where does this leave us? It is an exciting time to be doing sex research. Although it is still tough to recruit participants, our measuring techniques, informed and illuminated by new, biologically literate theory, are allowing us to make the bold predictions. Inevitably some of which will be followed by the conclusive refutations so beloved of philosopher of science Karl Popper.24 That is how we make progress, however, and the integration of different fields of science is one of the hallmarks that we are on the right track. One thing seems unlikely—that all of this effort and complexity just came about for no reason in particular.


1) Philip Stanhope, 4th Earl of Chesterfield (advice to son on the subject of sex)

2) Frederick, D. A., John, H. K. S., Garcia, J. R., & Lloyd, E. A. (2017). Differences in Orgasm Frequency Among Gay, Lesbian, Bisexual, and Heterosexual Men and Women in a US National Sample. Archives of Sexual Behavior, 1-16.

3) E.g. here

4) Wilder, J. A., Mobasher, Z., & Hammer, M. F. (2004). Genetic evidence for unequal effective population sizes of human females and males. Molecular Biology and Evolution, 21(11), 2047-2057

5) Kinsey, A. C., Pomeroy, W. B., Martin, C. E., & Sloan, S. (1948). Sexual behavior in the human male.

6) Isabella, R. A., & Belsky, J. (1991). Interactional synchrony and the origins of infant‐mother attachment: A replication study. Child development, 62(2), 373-384.

7) Safron, A. (2016). What is orgasm? A model of sexual trance and climax via rhythmic entrainment. Socioaffective Neuroscience & Psychology, 6.

8) Fleischman, D. S. (2016). An evolutionary behaviorist perspective on orgasm. Socioaffective Neuroscience & Psychology, 6.

9) Blumstein, Philip and Schwartz, Pepper (1983) American Couples. William Morrow

10) Csikszentmihalyi, M. (1996). Flow and the psychology of discovery and invention. New York: Harper Collins.

11) Darwin, C. (1872). The expression of the emotions in man and animals

12) Van Den Broek, E. M., & Todd, P. M. (2009). Evolution of rhythm as an indicator of mate quality. Musicae Scientiae, 13(2_suppl), 369-386.

13) Geary, D. C. (2015) Evolution of Paternal Investment in D M. Buss (ed) (2005). The handbook of evolutionary psychology. John Wiley & Sons.

14) King, R., & Belsky, J. (2012). A typological approach to testing the evolutionary functions of human female orgasm. Archives of sexual behavior, 41(5), 1145-1160.

15) Buzsáki, G., Anastassiou, C. A., & Koch, C. (2012). The origin of extracellular fields and currents—EEG, ECoG, LFP and spikes. Nature reviews neuroscience, 13(6), 407-420.

16) Chalmers, D. J. (1995). Facing up to the problem of consciousness. Journal of consciousness studies, 2(3), 200-219.

17) Singer, W. (2001). Consciousness and the binding problem. Annals of the New York Academy of Sciences, 929(1), 123-146.

18) McGurk H., MacDonald J. (1976). "Hearing lips and seeing voices.". Nature. 264 (5588): 746–8. doi:10.1038/264746a0. PMID 1012311.

19) Baars, B. J. (2005). Global workspace theory of consciousness: toward a cognitive neuroscience of human experience. Progress in brain research, 150, 45-53.

20) Buzsáki, G., & Watson, B. O. (2012). Brain rhythms and neural syntax: implications for efficient coding of cognitive content and neuropsychiatric disease. Dialogues Clin Neurosci, 14(4), 345-367.

Canolty, R. T., & Knight, R. T. (2010). The functional role of cross-frequency coupling. Trends in cognitive sciences, 14(11), 506-515.

21) Trost, W., & Vuilleumier, P. (2013). Rhythmic entrainment as a mechanism for emotion induction by music: a neurophysiological perspective. The Emotional Power of Music: Multidisciplinary Perspectives on Musical Arousal, Expression, and Social Control, 213-225.

22) Minsky, M. (1988). Society of Mind project. Final report (No. AD-A-200313/5/XAB). Massachusetts Inst. of Tech., Cambridge (USA). Artificial Intelligence Lab..

23) Heinzel, A., Walter, M., Schneider, F., Rotte, M., Matthiae, C., Tempelmann, C., ... & Northoff, G. (2006). Self-related processing in the sexual domain: a parametric event-related fMRI study reveals neural activity in ventral cortical midline structures. Social Neuroscience,, 1(1), 41-51.

24) Popper, K. (2005). The logic of scientific discovery. Routledge.

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