“A student asked, ‘Yeah, but do the wrinkles always form in the same way?’ And I thought: I haven’t the foggiest clue!” said German, a faculty member at the Thomas J. Watson College of Engineering and Applied Science’s Department of Biomedical Engineering. “So it led to this research to find out.”
I wish the authors would have mentioned the kid by name in the acknowledgement section of the paper. I bet the kid would have felt very proud and inspired to having their name published in a scientific journal.
That makes me wonder how many important results actually came from inquiries from curious students whose name was forgotten or purposefully ommited, lost from history. Any other similar examples? Student from Student's t-distribution was actually an engineer that had to adopt a pseudonym because of his employer, so I think it doesn't count.
It's because such research has no obvious initial use that the public must pay for it; no private enterprise will fund it, and often it will be useless knowledge, but occasionally someone will figure something out that unlocks a whole new understanding of the world.
This article instantly brought back memories of my childhood when my fingers would wrinkle after being in water too long. I used to think it was caused by the skin swelling from water, but it turns out it's actually due to blood vessels contracting—what a surprise! Even more amazing, this research not only answers a childhood question but can also be applied in forensic science, which I never expected!
Do we still retain curiosity about the world around us? Have I overlooked the huge potential hidden in small details? Curiosity is truly important， it always leads us to discover unexpected worlds.
> Do we still retain curiosity about the world around us?
If I don't, then it's mighty strange that I've been binging Groucho Marx interviewing random people from the audience in the 1950s show You Bet Your Life for the past few hours, and his fascinating interviews with Dick Cavette and William Buckley Jr.
Anyway yeah that's literally the main reason any of us are on HN. Besides procrastinating.
It's probably an evolutionary adaptation to give us better grip in the water. People with nerve damage who can't feel their fingers also don't get pruny fingers, so there's clearly a "get pruny" signal coming from the brain or at least higher up in the nervous system.
Most biometrics aren't easily hidden from your environment, everyone's constantly leaving fingerprints and handprints all over everything, shedding skin cells and other DNA material, face and irises can be easily photographed.
So it's kind of cool that a theoretical biometric could be stable over time and not easily leaked, that could take time to produce. Like some sort of cold storage biometric in the far future once certain biometrics become less useful after they're too easily lifted and replicated with new technology. Sort of like deprecating obsolete cryptographic protocols once they're too easily broken.
There should definitely be a scene in the next James Bond film where he rocks up to a top government facility and the guard hands him a terrycloth robe and directs him to an ultra sleek bathing cubicle
multiple times DNA got transferred between totally unknown people and wrong person got convicted... so more biometrics better.
obsolete cryptographic protocols are many times used as a fallback. some application gets response from malicious actor about not supporting such new crypto, so server falls back to older cipher.. lets say some 100s billion dollar companies use systems which behave like this still in 2025...
This actually made me smile. I usually wash my clothes by hand, and every time I do a big batch, I always get those wrinkly fingers never thought much of it.
It's kind of wild to realize there's actual research behind it. Even more surprising that it connects to forensic science and fingerprinting.
Science really does hide in the most ordinary places. I love this kind of curiosity.
The clothes last longer, and some fabrics don't like machine washing and using a bag for more than a couple things in the washer and dryer makes it even more of a chore.
I've hand-washed before, and I still "hand wash" pillows in a bathtub. If I had a lot of vintage shirts or something that I really liked I'd probably hand wash them in the kitchen sink.
A kids ask a question, science is getting done, we have answer to the question. Unless there was obvious yes or no before the science was done it is not ignoble worthy.
I often wondered how long we can stay in water before it becomes harmful. I used to imagine what might happen if I stayed submerged for hours. It wasn’t until later that I found out the skin wrinkling effect is actually caused by the nervous system reacting to prolonged exposure to water, which is believed to help improve grip.
But how long is too long? Prolonged immersion can lead to skin damage or dehydration, and the risk depends on water temperature and the individual’s condition. It’s fascinating how much our bodies can adapt, but it also reminds me how important it is to listen to our bodies and not push limits.
Does each body have a different tolerance to water immersion? Can we train our bodies to withstand longer periods, or is there a limit to what our skin can handle?
I am reminded of a theory years ago that fingers wrinkling in water might have an evolutionary function, specifically to improve our grip when wet (or in water).
The wrinkly formation lets water drain better (like treads of a tire).
Shampoo makers add ingredients which alter what you perceive with fingers. so if you wash your hair with gloves on hand, you can feel that shampoo did nothing to your hair. or try one hand with glove, other without and you can touch your hair to feel that scam.
also most shampoos, shower gels are just soap making ingredients + fragrance + color...
not walking on direct sun most of the day did more to beauty of current population than any beauty product on planet. yes im ugly.
I don't know the scope of "nothing" in your statement, but shampoo does help remove dirt and oil, in a way that washing with water only cannot achieve, which is the number one goal of using shampoo for most people.
This is verifiable by observing and touching hair of other people's hair before and after shower, which eliminates the possibility of shampoo manufacturers secretly altering what you perceive with your fingers.
> This is verifiable by observing and touching hair of other people's hair before and after shower, which eliminates the possibility of shampoo manufacturers secretly altering what you perceive with your fingers.
No; you would need to touch people hair after a shampoo shower and after a non shampoo shower to see the difference.
My very possibly wrong understanding is that plain water + the mechanical action of the water being sprayed on the hair + your hand scratching the scalp does a huge portion of the work. Shampoo itself does very little.
So if you don’t have any at your disposal; just does “as if”; and for slightly longer and you will essentially be good to go.
> No; you would need to touch people hair after a shampoo shower and after a non shampoo shower to see the difference.
Yes, that's exactly what I mean. My girl friend has long hair, and doesn't wash with shampoo every day (which is somewhat common for long-haired people I believe), and the texture after shower is very different.
In college, especially exam week, we had more anecdata. It was possible to see people who 1) had not washed their hair, 2) had washed their hair in a sink with water only, 3) dry-washed with those sprays, and 4) washed with shampoo. It was very easy to tell which they did.
In general, soapy cleaner (or similar substances) is going to help immensely when cleaning oily stuff. And hair can be really oily. Water-only is just not the same.
One scenario I don't have is comparing other soapy products to shampoo. But shampoo aren't more expensive than other soaps anyway, so I never bothered to look.
There are two types of people who don't shampoo every day: those who don't wash their hair every day, and those who wash their hair with water most days but shampoo only some days.
If your girlfriend is in group 2, then your experience is relevant to the parent's post; if she is in group 1, then you haven't yet experienced the difference.
I'm in both group 1 and 2 (I normally alternate between the two, i.e. soap - water - soap - no wash - soap...).
Washing with soap removes oils. This is a pretty obvious effect from anyone who's ever tried to clean up oil/grease with soap (ex: dawn).
Rinsing with just hot water distributes oils from the scalp down towards the ends and it removes a little bit of oil in the process.
Rinsing with cooler water is less effective at distributing oils but also loses less oil in the process.
Not washing allows grease/oils (and skin/dander) to build up on the scalp and saturate hair near the scalp.
-----
If you are just rinsing/scrubbing with water, it does a lot relative to not washing at all but there isn't really a comparison when it comes to soap's efficacy at stripping oils/making them semi-water soluble so they can be washed away.
Lol what, just try it ffs. I dont get why people make up such elaborate claims and never bother to test them trivially.
One example - I did ie yesterday shower at gym after workout, after sauna, but didnt have shampoo so just water, cold and warm. Then washed just my hair at home. Hair and skin without any oil in gym, but very different feeling and also behavior of hair when combing. Shampoo makes hair much smoother for example, also less tough / more bendy.
It's "soap" with a pH that is less than 7. It doesn't matter much for short hair, but washing long hair with actual soap makes the usefulness of shampoo obvious.
Actual soap, with a basic pH, makes hair very difficult to comb.
And yet, if I don’t shampoo for a few days and run my fingers through my hair, then there will be dirt under my fingernails. Would you argue that washing with water is enough?
Yeah, i meant as a not changing structure of hair. Open women magazine and read what adverts say their heavenly concoction allegedly does to your hair. It does not do that.
Your fingerprints are largely static according to all police forces. To me that implies that the skin on your fingers probably wrinkles in a largely constant way too when submerged in water. No evidence nor research done here - just fiat!
If this is new then CSI will probably have a new tool. I suggest investigating other areas of the body to see if the same holds.
Do we have toe prints? ... and does the wrinkling thing hold for toes?
And plenty of research has shown the police are wrong and fingerprints aren't super unique or static, that is just convenient for prosecuting cases. They are unique and static enough to differentiate between a handful of people you already have on a short suspect list in a shortish time frame usually, but once you start trying to sort populations by fingerprints or you find a random fingerprint and are trying to find some unknown person you don't know about, it falls apart and has fucked over a number innocent people.
Its like matching the make of a vehicle and their tire tracks. Yeah if you have someone you suspect, and you see he has the same tires and model of car as was reported, it likely is useful. But if you just try to blame the first person you find with the same model vehicle and the same tires despite the lack of other evidence, you are inevitably going to screw over some random innocent person. Fingerprints are less unique than someones face, and plenty of people have been thrown in jail because they merely looked like a suspect.
You can also lose your fingerprints the older you get. My mother in law is 65 and she has essentially no fingerprints (she used to have when younger though).
I believe loss of collagen also makes iPhone and Android and laptop fingerprint scanners perform much less reliably. I have no idea how border security scanners cope. I've noticed with seniors I help with digital life how they prefer face ID or pin, the fingerprint readers never seem to them to be as reliable.
Can confirm. Did a bunch of concrete work last summer, which ended up getting concrete inside my work gloves. Had to use passwords/windows hello all last summer.
> I have no idea how border security scanners cope.
They don't, cue Immigration officials being frustrated with seniors who are debarking after an international flight with a queue forming behind them....
Reminder that fingerprint forensics aren't nearly as infallible as people have been convinced they are and are based on an examiners opinion on a match.
That makes me wonder how many important results actually came from inquiries from curious students whose name was forgotten or purposefully ommited, lost from history. Any other similar examples? Student from Student's t-distribution was actually an engineer that had to adopt a pseudonym because of his employer, so I think it doesn't count.
[flagged]
It's because such research has no obvious initial use that the public must pay for it; no private enterprise will fund it, and often it will be useless knowledge, but occasionally someone will figure something out that unlocks a whole new understanding of the world.
It's publicly-funded venture capital for ideas.
IIRC even LASER was seen as a novely demonstration of quite an obscure effect…
Gladstone once asked Faraday about the usefulness of electricity, just saying.
Faraday's response: "Why sir, there is every possibility that you will soon be able to tax it!"
This article instantly brought back memories of my childhood when my fingers would wrinkle after being in water too long. I used to think it was caused by the skin swelling from water, but it turns out it's actually due to blood vessels contracting—what a surprise! Even more amazing, this research not only answers a childhood question but can also be applied in forensic science, which I never expected! Do we still retain curiosity about the world around us? Have I overlooked the huge potential hidden in small details? Curiosity is truly important， it always leads us to discover unexpected worlds.
> Do we still retain curiosity about the world around us?
If I don't, then it's mighty strange that I've been binging Groucho Marx interviewing random people from the audience in the 1950s show You Bet Your Life for the past few hours, and his fascinating interviews with Dick Cavette and William Buckley Jr.
Anyway yeah that's literally the main reason any of us are on HN. Besides procrastinating.
Yup, procrastinating and curiosity. That's why I'm here.
It reminded me of how brains form through wrinkling folds [^0], space filling curves[^1], and the emergence of form through origami[^2].
[^0]: https://www.livescience.com/47421-human-brain-wrinkles.html
[^1]: https://medium.com/@nico727272/drawing-hilbert-curves-using-...
[^2]: https://en.m.wikipedia.org/wiki/Miura_fold
It's probably an evolutionary adaptation to give us better grip in the water. People with nerve damage who can't feel their fingers also don't get pruny fingers, so there's clearly a "get pruny" signal coming from the brain or at least higher up in the nervous system.
I would assume that blood vessels contract to preserve heat, not to provide a better grip when swimming.
Nerves affect muscle movement and blood vessel growth.
do you really have better gripe with wrinkled fingers underwater?
yes. https://royalsocietypublishing.org/doi/abs/10.1098/rsbl.2012...
Most biometrics aren't easily hidden from your environment, everyone's constantly leaving fingerprints and handprints all over everything, shedding skin cells and other DNA material, face and irises can be easily photographed.
So it's kind of cool that a theoretical biometric could be stable over time and not easily leaked, that could take time to produce. Like some sort of cold storage biometric in the far future once certain biometrics become less useful after they're too easily lifted and replicated with new technology. Sort of like deprecating obsolete cryptographic protocols once they're too easily broken.
There should definitely be a scene in the next James Bond film where he rocks up to a top government facility and the guard hands him a terrycloth robe and directs him to an ultra sleek bathing cubicle
I heard next James Bond will be woman. Lets distribute this rumor.
Jane Bind, agent for the Department of National Security. Has (GNU Public) License to kill -9.
Interesting idea. I suspect that you could figure out someone's "pruneprint" from their fingerprint, but that's just a hunch I have no evidence for.
multiple times DNA got transferred between totally unknown people and wrong person got convicted... so more biometrics better.
obsolete cryptographic protocols are many times used as a fallback. some application gets response from malicious actor about not supporting such new crypto, so server falls back to older cipher.. lets say some 100s billion dollar companies use systems which behave like this still in 2025...
Downgrade attack is also how the stingray worked...
yes and no, i rather call that functionality in stingray as a secondary measure, most us does not have good signal anyway.
This actually made me smile. I usually wash my clothes by hand, and every time I do a big batch, I always get those wrinkly fingers never thought much of it. It's kind of wild to realize there's actual research behind it. Even more surprising that it connects to forensic science and fingerprinting. Science really does hide in the most ordinary places. I love this kind of curiosity.
> I usually wash my clothes by hand, and every time I do a big batch, ...
I have so many [legitimate] questions...
Why do you wash your clothes by hand?
The clothes last longer, and some fabrics don't like machine washing and using a bag for more than a couple things in the washer and dryer makes it even more of a chore.
I've hand-washed before, and I still "hand wash" pillows in a bathtub. If I had a lot of vintage shirts or something that I really liked I'd probably hand wash them in the kitchen sink.
Spoken as a true 1st world person!
As we continue to look for ways to slow down attacks, I didn't expect to have "have user wear wet glove for 30 minutes" on my bingo card.
Interesting idea though. Tracking biometrics through slow reproducible processes.
Definitely a contender for the 35th First Annual Ig Nobel Prize!
Maybe my memory is failing me but I could swear that somebody has already won an Ig Nobel prize for similar research to this?
A kids ask a question, science is getting done, we have answer to the question. Unless there was obvious yes or no before the science was done it is not ignoble worthy.
I often wondered how long we can stay in water before it becomes harmful. I used to imagine what might happen if I stayed submerged for hours. It wasn’t until later that I found out the skin wrinkling effect is actually caused by the nervous system reacting to prolonged exposure to water, which is believed to help improve grip.
But how long is too long? Prolonged immersion can lead to skin damage or dehydration, and the risk depends on water temperature and the individual’s condition. It’s fascinating how much our bodies can adapt, but it also reminds me how important it is to listen to our bodies and not push limits.
Does each body have a different tolerance to water immersion? Can we train our bodies to withstand longer periods, or is there a limit to what our skin can handle?
I am reminded of a theory years ago that fingers wrinkling in water might have an evolutionary function, specifically to improve our grip when wet (or in water).
The wrinkly formation lets water drain better (like treads of a tire).
Maybe, but more surface area would be my supposition that I may have heard before but cannot recall.
I should add my wrinkly fingers to my phone's fingerprint sensor, then. I very often can't unlock my phone because my hands are wet.
Shampoo makers add ingredients which alter what you perceive with fingers. so if you wash your hair with gloves on hand, you can feel that shampoo did nothing to your hair. or try one hand with glove, other without and you can touch your hair to feel that scam.
also most shampoos, shower gels are just soap making ingredients + fragrance + color...
not walking on direct sun most of the day did more to beauty of current population than any beauty product on planet. yes im ugly.
> shampoo did nothing to your hair
I don't know the scope of "nothing" in your statement, but shampoo does help remove dirt and oil, in a way that washing with water only cannot achieve, which is the number one goal of using shampoo for most people.
This is verifiable by observing and touching hair of other people's hair before and after shower, which eliminates the possibility of shampoo manufacturers secretly altering what you perceive with your fingers.
> This is verifiable by observing and touching hair of other people's hair before and after shower, which eliminates the possibility of shampoo manufacturers secretly altering what you perceive with your fingers.
No; you would need to touch people hair after a shampoo shower and after a non shampoo shower to see the difference.
My very possibly wrong understanding is that plain water + the mechanical action of the water being sprayed on the hair + your hand scratching the scalp does a huge portion of the work. Shampoo itself does very little. So if you don’t have any at your disposal; just does “as if”; and for slightly longer and you will essentially be good to go.
> No; you would need to touch people hair after a shampoo shower and after a non shampoo shower to see the difference.
Yes, that's exactly what I mean. My girl friend has long hair, and doesn't wash with shampoo every day (which is somewhat common for long-haired people I believe), and the texture after shower is very different.
In college, especially exam week, we had more anecdata. It was possible to see people who 1) had not washed their hair, 2) had washed their hair in a sink with water only, 3) dry-washed with those sprays, and 4) washed with shampoo. It was very easy to tell which they did.
In general, soapy cleaner (or similar substances) is going to help immensely when cleaning oily stuff. And hair can be really oily. Water-only is just not the same.
One scenario I don't have is comparing other soapy products to shampoo. But shampoo aren't more expensive than other soaps anyway, so I never bothered to look.
> doesn't wash with shampoo every day
There are two types of people who don't shampoo every day: those who don't wash their hair every day, and those who wash their hair with water most days but shampoo only some days.
If your girlfriend is in group 2, then your experience is relevant to the parent's post; if she is in group 1, then you haven't yet experienced the difference.
I'm in both group 1 and 2 (I normally alternate between the two, i.e. soap - water - soap - no wash - soap...).
Washing with soap removes oils. This is a pretty obvious effect from anyone who's ever tried to clean up oil/grease with soap (ex: dawn).
Rinsing with just hot water distributes oils from the scalp down towards the ends and it removes a little bit of oil in the process.
Rinsing with cooler water is less effective at distributing oils but also loses less oil in the process.
Not washing allows grease/oils (and skin/dander) to build up on the scalp and saturate hair near the scalp.
-----
If you are just rinsing/scrubbing with water, it does a lot relative to not washing at all but there isn't really a comparison when it comes to soap's efficacy at stripping oils/making them semi-water soluble so they can be washed away.
To clarify: in that anecdote, I'm talking about washing hair in shower, with hot water, with no shampoo.
Lol what, just try it ffs. I dont get why people make up such elaborate claims and never bother to test them trivially.
One example - I did ie yesterday shower at gym after workout, after sauna, but didnt have shampoo so just water, cold and warm. Then washed just my hair at home. Hair and skin without any oil in gym, but very different feeling and also behavior of hair when combing. Shampoo makes hair much smoother for example, also less tough / more bendy.
I sadly don’t have enough hair to actually test it myself :( but thanks for sharing your experience
That's an interesting and unique take.
Might I point out that combing and brushing are definitely affected by shampoo and conditioners?
Source: although I am bald now, I had up to a meter of hair at various points in my life.
> I had up to a meter of hair at various points in my life.
In total, or in parallel?
Many parallel strands each around a 1 meter in length. E.g. the ordinary, person-on-the-street concept of hair length.
Please pardon my ill-fated attempt at humor.
> meter of hair
Twisted Sister?
They had feet.
Shampoo is soap, yes. You say that like it's forbidden knowledge.
It's "soap" with a pH that is less than 7. It doesn't matter much for short hair, but washing long hair with actual soap makes the usefulness of shampoo obvious.
Actual soap, with a basic pH, makes hair very difficult to comb.
Well, adverts made many believe shampoo is tears of virgin goddess.
> you can feel that shampoo did nothing to your hair
Huh? It removes oil and dirt.
If I go for a couple days without washing my hair it gets greasy and gross. Water by itself doesn't remove oil buildup.
And yes of course it's like soap. But it's milder. Technically it's a detergent because soap is too harsh.
I've never heard anyone say shampoo is a scam, this is definitely a first...
> I've never heard anyone say shampoo is a scam, this is definitely a first...
Well it's not a scam, it's a sham. Don't settle for fakes, demand real poo! :)=
I wish they could borrow my scalp and hair for a week. They would definitely not feel like shampoo is a scam.
Some people have been saying it, but it's not a common story: <https://www.youtube.com/watch?v=T-_HKFjxVl0>
And yet, if I don’t shampoo for a few days and run my fingers through my hair, then there will be dirt under my fingernails. Would you argue that washing with water is enough?
Depends how long of a fingernail are we talking !
Yeah, i meant as a not changing structure of hair. Open women magazine and read what adverts say their heavenly concoction allegedly does to your hair. It does not do that.
I don't doubt that their claims are fantastic rubbish, but you're verifying this by.. feeling the difference with gloves on/off?
This is going to be my favorite new conspiracy theory - BigShampoo.
Yeah, those tiny companies Unilever and J&J in the US, they wouldn't make things up just to sell us a chemical cocktail.
Your fingerprints are largely static according to all police forces. To me that implies that the skin on your fingers probably wrinkles in a largely constant way too when submerged in water. No evidence nor research done here - just fiat!
If this is new then CSI will probably have a new tool. I suggest investigating other areas of the body to see if the same holds.
Do we have toe prints? ... and does the wrinkling thing hold for toes?
And plenty of research has shown the police are wrong and fingerprints aren't super unique or static, that is just convenient for prosecuting cases. They are unique and static enough to differentiate between a handful of people you already have on a short suspect list in a shortish time frame usually, but once you start trying to sort populations by fingerprints or you find a random fingerprint and are trying to find some unknown person you don't know about, it falls apart and has fucked over a number innocent people.
Its like matching the make of a vehicle and their tire tracks. Yeah if you have someone you suspect, and you see he has the same tires and model of car as was reported, it likely is useful. But if you just try to blame the first person you find with the same model vehicle and the same tires despite the lack of other evidence, you are inevitably going to screw over some random innocent person. Fingerprints are less unique than someones face, and plenty of people have been thrown in jail because they merely looked like a suspect.
You can also lose your fingerprints the older you get. My mother in law is 65 and she has essentially no fingerprints (she used to have when younger though).
I believe loss of collagen also makes iPhone and Android and laptop fingerprint scanners perform much less reliably. I have no idea how border security scanners cope. I've noticed with seniors I help with digital life how they prefer face ID or pin, the fingerprint readers never seem to them to be as reliable.
Can confirm. Did a bunch of concrete work last summer, which ended up getting concrete inside my work gloves. Had to use passwords/windows hello all last summer.
> I have no idea how border security scanners cope.
They don't, cue Immigration officials being frustrated with seniors who are debarking after an international flight with a queue forming behind them....
https://www.ifsecglobal.com/access-control/why-age-is-not-ju...
Reminder that fingerprint forensics aren't nearly as infallible as people have been convinced they are and are based on an examiners opinion on a match.
https://pubmed.ncbi.nlm.nih.gov/32990979/
So my fingers are basically running the same wrinkle playlist every time I take a long bath — who knew!
isn’t that obvious?
Ah, the science frontier. Just imagine the possibilities now!