The topic of sex remains a taboo in some corners of society, but evidence of our interest in sex abounds:

• Viagra, a product treating male erectile dysfunction, enjoyed a peak revenue of approximately $2 billion
• The market for adult entertainment (a euphemism for looking at naked people doing sexy stuff) is estimated to be $75 billion in 2030
• #SpicyBookTok has peaked the interest of more than few women (I’m looking at you Ali Hazelwood), with romance sales being up 24% so far this year

I for one am a fan of the topic of sex. I actually started my career working on sex and parental care of insects, a group which are less complicated than people but do seem interested in sex all the same. I continue to believe that satisfaction in that domain is an important component of life and the WHO agrees. Now that doesn’t mean that everyone necessarily has the same preferences. I think diversity is the spice of life when it comes to sex, as long as it’s consensual. By extension, understanding what “turns us on” is therefore something worth exploring in my mind. So research attempting to understanding preferences that may not be mainstream do occasionally peak my interest. which brings us to to the topic sex robots…

Who is Looking Forward to the Rise of the Sex Robots?

It is with this in mind, that I recently fully immersed myself in a study from 2021 by Brandon and Planke called “Emotional, sexual and behavioral correlates of attitudes toward sex robots: Results of an online survey.” There are string of these studies as of late (eg Hot for Robots! Sexual Arousal Increases Willingness to Have Sex with Robots, Technically in love: Individual differences relating to sexual and platonic relationships with robots), which makes me think there is a subset of the scientific community that is wondering why we aren’t having more robot sex? While that may be fair question, I would like to take minute to topline Brandon and Planke’s paper, because I think this study is both instructive and in some ways representative of this literature:

• 106 men, 205 women, and 5 non-binary respondents, sampled by “crowdsourcing techniques“, took a 27 question unvalidated survey “developed to investigate attitudes toward sex robots”
• 8% of survey respondents expressed an interest in having sex with a robot
• 19% of survey respondents said they looked forward to a time when sex robots were easily available
• In a finding that I’m sure surprises virtually no one, males reported a greater interest in sex robots than females (p<0.001)

Now as much as I love the idea that more than 1 in 5 men are enthusiastically awaiting the arrival of sex robots I’d like to take a beat at this point and consider study design. This is a self reported survey, whose questions mean god knows what to to god knows who, and the respondents were selected god knows how (I’m assuming “croudsourcing” means vibes were involved but I can’t independently confirm that). As much as I want to believe these conclusions, I’m often reminded that the only thing that people love more than results from surveys like this, is messing with people who administer surveys like this.

Take for example the following findings from research focused on teens as reported by NPR:

In a 2003 study, 19 percent of teens who claimed to be adopted actually weren’t, according to follow-up interviews with their parents. When you excluded these kids (who also gave extreme responses on other items), the study no longer found a significant difference between adopted children and those who weren’t on behaviors like drug use, drinking and skipping school. The paper had to be retracted. In yet another survey, fully 99 percent of 253 students who claimed to use an artificial limb were just kidding.

While I’d love to assume that teens were the outlier, a few quotes from the text make me suspicious that ~1/5th of the population isn’t just a little mischievous:

1. “[E]very emotional, sexual, and behavioral variable we investigated correlated positively with attitudes toward sex robots”
2. “Half of our sample acknowledged struggling with one of the four mental health concerns we assessed… each of these disorders correlated with more positive attitudes toward sex robots”

I interpret this as a high proportion of outlier answers which correlated with a greater desire to have sex with robots… which as earlier studies indicate may be people “just kidding.” I can’t definitively prove that at this moment but it does make me very suspicious of these results.

How Do We Tell If Someone Is Experiencing Sexual Arousal?

While I feel quite confident that I can self identify when sexual arousal is happening to me, I really question how we make this assessment in others. After all, people like to lie about things like this so just asking them is sub-optimal.

In the late 19th and early 20th centuries, Sigmund Freud dominated the conversation. For him, sexual arousal was mostly about unconscious drives, repression, and whatever your mother did when you were three. The problem? There wasn’t much in the way of actual data to support his conclusionz.

It wasn’t until the 1940s and 1950s, when Alfred Kinsey and colleagues at Indiana University began interviewing thousands of Americans about what they actually did in bed that things got more data driven. The Kinsey Reports revealed sexual practices were far more diverse than polite society would like to admit. It wasn’t physiology yet, but it cracked open the door for scientific investigation of arousal.

In the 1960s, William Masters and Virginia Johnson decided to measure the body directly. They wired up volunteers in their St. Louis lab, tracking penile tumescence (AKA erection), vaginal lubrication, heart rate, and muscular contractions while participants engaged in sexual activity. Their 1966 book Human Sexual Response defined the four-stage cycle of sexual response:

• Excitement phase
• Plateau phase
• Orgasm phase
• Resolution phase

Following Masters and Johnson there was a greater emphasis placed on penile plethysmography, which measure blood flow and circumference of the penis, and vaginal photoplethysmograph, which attempted to detect vaginal and clitoral blood flow. Interestingly while one may expect the primary discussion on penile plethysmography to center around erectile dysfunction (or at least I did), there is a very active area of legal discussion related to sex offenders in the US (which I’m arbitrarily deciding is beyond the scope of this post).

Studies into the 2000s have layered on neuroimaging data that uses techniques like fMRI to identify brain areas such as the amygdala and hypothalamus that appear important for sexual desire/arousal. While such brain imaging is less invasive, it ultimately is plagued by the general ambiguity of brain activity (ie cool you identified a new brain region… now what the hell do I do with that info).

The Resolution Phase

Sexual biology is complex, this isn’t easy stuff. It’s easy to critique but it’s much harder to do a robust study in this space. Arousal is multidimensional thing, including not just plesmography, fMRIs and maybe a hormone assay for good measure with a healthy dose of erotic slide shows. Nothing is perfect and this is an evolving area of research.

That said if someone wants to do a large (N=1,000) multi-method cross cultural study including a validated questionnaire with bogus items (eg “I’ve owned a functional android partner built before 1990”) and that includes recontact verification to confirm extreme answers; I’m really interested in your study results. My choice to substantially invest in sex robots hinges on your study findings.