Whose headache is worse?
It started with a dumb argument.
Someone close to me and I both had a headache on the same day. We both called it a 7 out of 10. Then the obvious question: whose was actually worse?
I figured science had an answer. It doesn’t. But what it does know turned out to be way more interesting than winning.
The problem in one line
I can’t feel your pain, and you can’t feel mine.
Your brain can tell when one of your eyes sees worse than the other, because both eyes feed the same brain. No brain ever gets two people’s headaches to compare.
The philosopher Ludwig Wittgenstein had a picture for this. Everyone has a box with something inside they call a “beetle”. You can only look in your own box. We all talk about our beetles anyway, and nobody can ever check if they’re the same thing. Pain is the beetle.
An economist, William Stanley Jevons, got there even earlier, in 1871. He wrote that one person might feel things a thousand times more strongly than another, and we’d have no way to tell.
Three places we can be different
Between “my head hurts” and “it’s a 7” there are three steps. Two people can differ at every one.
1. The signal
Some people are born feeling no pain at all. In 2006, scientists described a boy in northern Pakistan who did street stunts. Knives through his arms. Walking on hot coals. He felt nothing, because one gene, SCN9A, was broken and his pain nerves couldn’t fire.
He died before his 14th birthday, after jumping off a roof. Pain is annoying. It’s also the thing that keeps you alive.
2. The volume
This is the part that got me.
In 2003, Robert Coghill’s team put the exact same heat, 49°C, on the back of the lower leg of 17 people. Then they asked how much it hurt.
Same heat. 17 people. How much did it hurt?
You’d think the high scorers were exaggerating. They weren’t. Their brain scans matched their words. People who said it hurt more had more activity in the parts of the brain that feel and judge pain. The thalamus, an early relay station, looked the same in everyone. The difference showed up later.
And when people were tested again, their ratings barely moved. It’s a trait, not a mood.
3. The words
Even if two people felt the exact same thing, they could still pick different numbers. Your 10, “the worst pain imaginable”, depends on what you can imagine. If the worst thing that ever happened to you is a stubbed toe, your 10 is not my 10.
The taste scientist Linda Bartoshuk calls this measuring with an elastic ruler. Her fix is clever: rate everything against something that doesn’t stretch, like how loud a sound is.
Can’t a brain scan just settle it?
I hoped so. In 2013, Tor Wager’s team found a brain pattern they called a pain signature. It’s honestly impressive:
- It told painful heat from plain warmth at least 94% of the time.
- When people got a strong painkiller, it dropped by 53%, even when they didn’t know they’d been given one.
- It ignored heartbreak. People looking at a photo of an ex who dumped them didn’t set it off.
So, case closed? No. Here’s the catch.
94%
Is this one person in pain right now? The scan gets it right this often.
~4%
Who feels more, you or me? That's how much of it the same signature explains.
Tracking one person’s pain going up and down is one job. Comparing two people is a different one. In 2022, Coghill’s own lab scanned 101 people and couldn’t find a brain signal that said who feels more. A 2024 study of 124 people found the 2013 signature explained only about 4% of who rated pain higher. Newer brain patterns do a bit better, but nobody can read your 7 off a scan.
Weirder still: two people born unable to feel pain were scanned while being pricked with a pin. Their so-called pain areas lit up just like everyone else’s.
So a scanner can tell that your pain went down. It can’t tell if your 7 is bigger than mine. In 2017, a panel of experts said brain scans aren’t ready to be used as pain lie detectors.
Why this matters
Because pain can’t be seen, people doubt it. We tend to underestimate other people’s pain, and doctors and nurses do it too.
In one 2016 study, about half of the white medical students and residents believed at least one false thing about Black people’s bodies, like having thicker skin. The ones who did rated a Black patient’s pain lower.
In 2020, the main pain science group, the IASP, rewrote its definition of pain. One of the notes says a person’s report of pain should be respected. Since nobody can open the box, the report is all we have.
So who won?
Nobody. Both 7s were real, and there’s no ruler on Earth to compare them. I stopped arguing.
What I actually took away:
- When someone says 7, believe the 7. It’s the only measurement there is.
- The change matters more than the number. A drop of about 2 points, or 30%, is when people feel real relief. Going from 7 to 5 is a big deal.
- One exception to “it’s just a headache”: if a headache hits full strength in under a minute, that’s an emergency. Get help.
Sources
- Coghill, McHaffie and Yen (2003). Neural correlates of interindividual differences in the subjective experience of pain. PNAS.
- Cox and colleagues (2006). An SCN9A channelopathy causes congenital inability to experience pain. Nature.
- Wager and colleagues (2013). An fMRI-based neurologic signature of physical pain. New England Journal of Medicine.
- Hoeppli and colleagues (2022). Dissociation between individual differences in self-reported pain intensity and underlying fMRI brain activation. Nature Communications.
- Gim and colleagues (2024). Interindividual differences in pain can be explained by fMRI, sociodemographic, and psychological factors. Nature Communications.
- Salomons, Iannetti, Liang and Wood (2016). The “pain matrix” in pain-free individuals. JAMA Neurology.
- Davis and colleagues (2017). Brain imaging tests for chronic pain: medical, legal and ethical issues and recommendations. Nature Reviews Neurology.
- Prkachin, Solomon and Ross (2007). Underestimation of pain by health-care providers: towards a model of the process of inferring pain in others. Canadian Journal of Nursing Research.
- Hoffman, Trawalter, Axt and Oliver (2016). Racial bias in pain assessment and treatment recommendations, and false beliefs about biological differences between blacks and whites. PNAS.
- Raja and colleagues (2020). The revised International Association for the Study of Pain definition of pain. Pain.
- Farrar and colleagues (2001). Clinical importance of changes in chronic pain intensity measured on an 11-point numerical pain rating scale. Pain.
- Bartoshuk and colleagues (2004). Valid across-group comparisons with labeled scales: the gLMS versus magnitude matching. Physiology & Behavior.
- Jevons (1871). The Theory of Political Economy.
- Wittgenstein (1953). Philosophical Investigations, section 293.