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So what hurts more: being kicked in the crotch or giving birth? If you're a guy you'd likely argue strongly for being kicked in the nards.

Whereas many women would be inclined to argue childbirth. But can science settle the debate once and for all? Nope! ...

Or at least not yet. Basically everyone feels pain. But the experience is incredibly subjective.

How you feel pain can be influenced by a ton of different factors. And that's why answering this question is almost impossible. That's not to say we haven't made great strides in our understanding of the neuroscience or physiology of pain.

We now have tools like neuroimaging that let us see what parts of the brain are used when we feel pain. We also have electroencephalography, also known as EEG, that can measure the intensity of brain activity when we're in pain. And there's even the promise of blood tests finding biomarkers for pain.

However, many of these advances are still very much in the early stages of research, so they still can't actually tell us what hurts more. But if we were gonna try and answer it, this is what we'd need to figure out.

One: We need to know how much it hurts. You've probably been asked by a doctor at some point how much something hurts. They hold up a scale with emoji faces numbered one to ten, and you try to translate their goofy expressions into what you're actually feeling. Because the thing about your pain is, only you can feel it, so doctors need you to tell them.

But as anyone who's encountered this system knows, it's far from perfect. The science of measuring pain has a surprisingly short history. In the 1940's, a group of researchers from Cornell University developed a device called the dolorimeter.

This marvel of medical engineering essentially just applied a controlled dose of heat. The instrument got as hot as 45 degrees Celsius, and could cause serious burns. They then came up with a scoring system that used a unit called a ‘dol' to record the intensity of the pain.

In nineteen fifty-one, the dolorimeter inventors used their creation on patients to see how effective various pain meds were during childbirth. Strangely enough, this ended badly. At least one patient got so upset at being poked with a burny probe that researchers had to lay off testing them.

Which, I mean, they were being poked with a burny probe while giving birth. So. The dolorimeter was largely abandoned soon after.

In its place, the familiar one to ten scale was developed. In 1966, a pair of UK psychiatrists asked patients to make a pencil mark on a ten centimeter line between the phrases “I have no pain at all” and “My pain is as bad as it could possibly be.” They measured the distance to the pencil mark and assigned a pain score from zero to ten. This and other efforts led to the pain scale.

Sometimes these scales come with those grimacing emoji faces, but they're all pretty basic. And when it comes to evaluating and treating pain, having a basic numerical scale doesn't really cut it. Mostly because pain is complex and multidimensional, and doesn't really fit on a linear spectrum.

Is it continuous or temporary? Stabby or dull? Is it stopping you from concentrating?

And so on. The McGill Pain Questionnaire, introduced in 1975, attempted to address this complexity. It was designed to capture all the dimensions of pain, as well as its intensity.

It's been widely accepted by doctors, and it's still used today. It has almost eighty descriptors for pain – like stabbing, radiating, shooting, and so on. But there are still some pretty big limitations to it.

Language is one of them. Like, how can you tell the difference between one person's ‘nagging' pain and another person's ‘annoying' pain? Critics have also pointed out that the questionnaire relies on a pretty advanced vocabulary, so the questionnaire might not work very well for people who struggle with reading or writing.

In fact, one meta analysis from 1990 found that only 19 of the 78 descriptors were picked by more than twenty percent of the subjects. Another problem is that versions in other languages, such as French or Japanese, may not have exact matches for the words in the original English version. That makes it hard to compare different populations.

Plus, very few of the other versions have been thoroughly tested to see if they work as well as the English version. In short, relying on self-reports of pain is kind of like playing those word games where you throw out words to complete a story. Sometimes the words you choose work, and the sentence makes sense -- but a lot of the time it's complete nonsense.

However, when you can see the whole sentence, picking a word that fits is a no-brainer. So wouldn't it be great if we could see when someone's in pain? A part of the brain that lights up like a Christmas tree when you've just dumped a cup of hot coffee on yourself?

Using functional magnetic resonance imaging, otherwise known as fMRI, neuroscientists have identified a few parts of the brain – including the anterior cingulate cortex, thalamus and insula – that light up on brain scans in response to pain. These areas together are known as the pain matrix, and it has been suggested that they could serve as a measurable signature of pain. Some researchers have gone so far as to use the pain matrix to prove that social pain, like being rejected, and physical pain can be the same.

But not all neuroscientists are on board. Some have called the validity of the pain matrix into question. In a study published in 2016, researchers scanned the brains of two people with congenital insensitivity to pain.

Patients with this disorder can't feel physical pain. Their brains were compared to those of four healthy participants. When these people were pricked with a pin, the researchers found that similar areas of the brain lit up in both groups.

In other words, the pain matrix is probably responding to something other than just pain. That's not to say that the pain matrix isn't involved in processing pain, but just because it lights up doesn't actually mean that someone is in pain. So answering the question ‘how much does it hurt?' is way more complicated than pointing to a number on a scale.

And it's even more complicated than having a brain scan done to see how much your brain lights up when you're kicked in the gonads versus pushing out a baby. The second thing we'll need to answer our question of what hurts more is a way to compare pain experiences. This can be tricky.

Especially since even comparing your own personal pain experiences can be hard. Like, what hurts more: stubbing your toe or being hung over? But since your average person won't be able to experience both giving birth and being kicked in the nards, we need to be able to compare levels of pain.

And that's a challenge because historically, research has barely even looked at how women experience pain. Until recently, pain research has mostly excluded women. Clinical trials tended to focus on white men, viewing them as a default population to study.

In 1977, an FDA guideline effectively banned women of childbearing age from participating in many clinical trials because they were considered a “vulnerable population.” They seemingly didn't want to risk damaging a fetus if a woman just so happened to become pregnant during a study. Even female mice have historically been excluded, based on the argument that hormonal cycles would introduce too much variability. One analysis published in 1995 found that almost eighty percent of animal studies of pain in the previous ten years had used only male mice.

This is despite the fact that the majority of people who suffer from chronic pain are women. And historically, some researchers haven't even bothered to report what sex their rodents were. Even rodents can't catch a break from gender bias!

But there really are observable differences between how men and women feel pain. For example, one 2012 study examined medical records from more than 11,000 patients reporting pain for a wide variety of conditions. It found that women consistently rated their pain as more intense on the good old one to ten scale.

Another study published in 2019 in the journal Brain looked at neuropathic pain, a particular type of chronic pain. It found differences in gene expression in the nerves of men and women with this type of pain. It's also worth noting that most of these studies have been done with cisgender individuals, or failed to account for transgender or nonbinary people within their study population.

So how people who don't fall into the cisgender category process and feel pain is still relatively unknown. One 2007 study involving 47 trans women and 26 trans men found that the men had fewer pain problems after they started taking testosterone. Conversely, the women were more likely to report pain issues after hormonal transition.

And this could be because hormones, like testosterone and progesterone, have been shown to play a role in pain sensitivity and pain relief -- though other factors, including social ones, couldn't be ruled out. So way more research is needed into how and why these differences exist. Until we know more about how different genders experience pain, we can't really address everyone's pain properly.

Plus, pervasive myths about how women handle pain have endured well into the twenty-first century. For example, a 2018 review of the literature found some researchers assume that women are inherently good at dealing with pain because they've experienced menstruation or childbirth. Obviously, that's not true.

That same analysis also found that women are more likely to be seen as overly sensitive or even hysterical, compared to men being perceived as stoic. And this means women are more likely to be ignored or undertreated for their pain. To make comparing pain even harder, race, ethnicity and cultural differences have also been shown to play a role in how people experience pain.

A review published in 2012 showed that certain non-white minorities in the US tend to be more sensitive to pain. For example, African-Americans participants report greater pain sensitivity than white participants. Cultural factors may also play a role.

For example, one 2009 study found that Asian patients were more likely than other groups to try to conceal their cancer-related pain. And just like misconceptions about women, racial biases also rear their head when it comes to assessment and treatment of pain. A study published in 2016 found that some medical professionals may hold misconceptions about biological differences between black people and white people that inform their medical judgments.

Like assuming that black people have thicker skin -- which is nonsense. They also found that medical professionals who believed in these myths rated black patients' pain as lower and gave them less adequate treatment. Research has consistently shown that black Americans are frequently undertreated for pain in comparison to white Americans.

In fact, some experts have suggested that these attitudes have extended toward differences in the prescription of opioids to black and white patients -- and corresponding disparities in the way the opioid epidemic has played out in both groups. With all that in mind, can we actually objectively measure pain with no biases? Not yet -- but researchers are trying.

With advances in neuroscience it seems like we're getting closer to that holy grail. But as of right now there's no one thing that can objectively measure pain without bias. And maybe that's the problem.

We're looking for one thing that will let us objectively measure pain. But there's so many things that go into how pain feels that getting an accurate read on how much pain someone is in might take a battery of tests and questionnaires to determine. Either way it seems the question of what hurts more – being kicked in the crotch or childbirth – will remain a scientific mystery.

For now. Thanks for watching this episode of SciShow, and a huge thank you to our patrons for making what we do possible. If you want to support us directly and join a community of super awesome super great people, check out patreon.com/scishow. [ outro].