Australian Scientist Wins IgNobel Prize for Belly-Lint Study

Dr Karl is a real scientist, who has a hilarious section in the Australian National Broadcaster's website, and life.

Some Abuzzers will recall him as the brains behind Moondoggy's hilarious thread on whether farts spread germs - (not if you are wearing undies, it seems) and the fart proof undies.

Dr Karl has won a 2002 Ig Nobel Prize for the Belly Button Lint Survey!



Dr Karl was at the Boston event to receive this most prestigious award.

The take-home answer on lint...
You're more likely to have Belly button Lint (BBL) if you're male, older, hairy, and have an innie.

More specifically...


+ You get more BBL as you get older
+ More men have BBL than women
+ Lint colour reflects your skin tone - lint is lighter for light skinned people.
+ Skin type does not affect BBL.
+ BBL appears to be related to hairiness.
+ Too much belly hair, or too little belly hair somehow inhibits the movement of BBL into the belly button.
+ There is no relationship between BBL and a person's overall build.
+ Anecdotal evidence suggests that navel rings dramatically reduce BBL or even remove it altogether.
+ It seems as though the Snail Trail has something to do with BBL levels.


Most of our 4799 respondents heard about the survey from triple j , but we did get worldwide publicity from New Scientist.

Read the in-depth results, check out the piccys, laugh at other people's quotes and be boggled by our bellybutton facts. Find out why we decided to do a bellybutton lint survey or check out a couple of theories on lint production.

And most importantly, thankyou to everyone who contributed to Dr Karl's bellybutton lint survey.

here is more detail:

Quotes from participants:

http://www.abc.net.au/science/k2/lint/quotes.htm

Dr Karl's website

http://abc.net.au/science/k2/default.htm

Bellybutton facts:

http://www.abc.net.au/science/k2/lint/facts.htm

Pictures of Lint under microscopy.

http://www.abc.net.au/science/k2/lint/pictures.htm

Theories:
Early Theories of Bellybutton Lint (BBL)

Research always starts off with a few tentative probes into the unknown. Later people benefit from this early work. Isaac Newtown said, "If I have been able to see far, it is because I have stood on the shoulders of giants."

Tim Albert was one of these giants. Back in August 1984, Tim Albert was the Editor of the British Medical Association (BMA) News Review. A researcher from a BBC radio program had asked the BMA office why men (but not women) get bits of blue Lint in their navels. The BMA News Review posed this question to its readers, and then Tim Albert published their answers about Belly Button Lint (BBL) in an article entitled "Blue jokes - Readers probe the mysteries of the navel". Peter d'Abrumenil made a telling comment: statistical studies of BBL might not be valid if there is no nudist control group.

Professor Wil's theory of BBL - The comedian Wil Anderson (also known as Professor Wil) has his own theory of BBL. He claims that the body hates colours, and will expel them through the nearest orifice. So green snot leaves via the nostrils, brown faeces via the anus, yellow urine via the urethra and, yes, blue Belly Button Lint via the belly button.

Peter Johnson and Geoffrey B. Scott from the Department of Pathology at the University of Aberdeen very cleverly observed that "abdominal body hair tends towards the umbilicus, as roads to Rome. It is our contention that particles of Lint caught in this bristly trap are cast navelwards under the influence of body movement."

Of course, this Hair Transport Theory would easily explain why there seems to be less BBL in women that in men - because women have less body hair. Several readers observed that BBL is not always pure blue in colour, and appears to be related to the colour of the clothing worn.

It's worth noting that blue is a very popular clothing colour in our current society. On most days, most people wear various shades of blue. This might explain why blue is such a common colour in BBL.

Another Theory of BBL

Michael Biesecker also discussed BBL in the 19 April 1995 issue of Technician (the student newspaper of North Carolina State University). His theory was similar to Tim Albert's - that the process involves fibres leaving clothes and being funnelled to the belly, where they coalesce into balls of lint. He wrote that the colour of the BBL is related to the colour of the clothing you wear. But those who wear many different colours usually still generate BBL with the same blue-grey colour that you find in the lint collector of clothes dryers. He says that hairy stomachs are associated with greater quantities of BBL - possibly because the hair both dislodges the Lint from clothing and channels it to the belly button. He also says that larger bellies are associated with more BBL -perhaps because larger bellies have deeper navels.

The Real Question:
Why do a Bellybutton Lint Survey?

For ever good survey there's a good story behind it...

It all began innocently with a simple question on Dr Karl's Triple J Science Talkback radio show.


"Why is my Belly Button Fluff blue - and why do I get it, anyhow?

This was a real question, and it deserved a real answer. So we went looking.

We couldn't find any surveys involving large numbers or any hard research involving microscopes. But we did find a few theories.

However, Dr Karl tries to avoid opinions, and to stick to the facts. The lack of hard data should have been the end of the Belly Button question. But then the Soft Bottom Inshore Fish Habitats Research Team sent him an amazing email about their previously unknown (to Karl) friend called Doug.

Doug shaves around his navel - Doug was a Prince Among Men. Instead of just sitting down and thinking, Doug Had 'Done the Experiment'. Doug suffered from/enjoyed BBL. He thought that the hair on his belly was "channelling and concentrating lint from his clothes into his belly button". So he decided to test this theory.

The Experiment - He shaved his belly over a 10-cm radius around his navel. Suddenly, Doug stopped generating BBL. Doug also noticed that as his belly hair regrew, the BBL reappeared in his navel. He then made another very interesting observation. He noticed that the BBL was usually the colour of the underwear below his waist, and not that of his upper body clothing. Perhaps, he suddenly thought, the BBL was being channelled by a Hair Highway (Snail Trail) running upward from his pubic hair to his belly button. This was a reasonable guess. So Doug Did the Second Experiment.

Doug shaves his lower belly - He tested his guess by shaving the hair from part of his Snail Trail, in a horizontal band across his lower abdomen (not from around his navel, as before). This effectively created a hair-free roadblock. Again, the BBL suddenly stopped.

Our response? - This unexpected email shamed Dr Karl into action. If Doug, all by himself, could Do an Experiment - then so could we. Thanks to the internet, it was all so much easier than it would have been 10 years earlier. We set up a BBL survey on Dr Karl's webpage, and left it running for two months in late 2000.

What was going on?

Our Working Hypothesis (science talk for "Reasonable Guess") had two parts. We definitely did not think that the belly button generated its own BBL. (However, Professor Wil disagrees - see theories ).

The first part of our guess was that at least some of the BBL was made from clothing fibres (although there might be other stuff in there as well, such as your own hair, or skin cells). These fibres might fall out because the clothes were getting old and threadbare, or perhaps because your washing machine or clothes dryer was too brutal on your clothes (which is why dryers have lint filters).

The second part of our hypothesis was that the hair on your belly acted like a one-way ratchet mechanism, and advanced the loosened clothing fibres towards the belly button.

Our Experiment

A hypothesis is just "spinning your wheels", unless you follow it up with an experiment. When Dr Karl was a physicist, he did experiments. When he became a biomedical engineer (designing and building a machine to pick up electrical signals from the human eyeball), this suddenly changed. He was told that research work related to humans was not called an "experiment", it was a "study". His boss told me that was because people get quite anxious when you want to do an "experiment" on them - but not nearly so anxious if you just want to do a "study". But most people understand what an "experiment" is, so let's call it "Our Experiment".

Our Experiment had two parts: the survey, and the practical work. Our survey asked 19 questions. We even asked the participants to get mega-involved, and shave their bellies to do the Hair-Free Highway Experiment.

But we also wanted to understand more about the physical structure of BBL. So we asked people to send in samples of their own personal BBL, and then looked at them under various microscopes.

Survey Questions

1. First name (optional):
2. Age:
3. Sex:
4. Degree of overall hairiness:
5. Do you have a Snail Trail?
6. Degree of Snail Trail hairiness:
7. Innie/Outie?
8. Describe your build:
9. Skin colour:
10. Skin type:
11. Do you have a navel ring?
12. Do you get Belly Button Lint?
13. If so, what colour is it?
14. Have you noticed that your Belly Button Lint colour is related to the colour of your clothing?
15. If so, what clothing?
16. Do you wash your clothes in a top-loader or a frontloader?
17. Did you undertake the Hair-Free Highway experiment?
18. If yes, did you notice a decrease in Belly Button Lint?
19. Any other comments on Belly Button Lint:

The Results:

The Bellybutton Lint Survey Results

The results of our world-first bellybutton lint survey can be easily summarised as follows:


You're more likely to have BBL if you're male, older, hairy, and have an innie.

4799 people answered our survey. They were 58.1% male (2790) and 41.9% female (2009). Only 66% (3169) of these people had BBL.

Age - We asked people into which five-year age group they fitted, ranging from 16 to 75. The numbers in each age category dropped off evenly with age. There were the greatest number of respondents (768) in the 16-20 group, and the lowest (3) in the 71-75 group. There were still enough in the 51-55 age group (62) to do meaningful statistics. The clear result was that the older you get, the more BBL you get.

Sex - The majority of those with BBL were male (73%, 2313), while the minority were female (27%, 856). Males tend to have more hair than females, so this fits our Hair-Causes- BBL Theory.

Degree of overall hairiness - Hairiness seemed to be related to BBL. About 97% of those who had BBL were either "not very hairy", "moderately hairy" or "very hairy".

Hair track directs joeys - Marsupials give birth to their young outside their pouch. The joey (the baby kangaroo) has to find its way to the pouch, by following a "track" in the fur of the mother kangaroo. Inside the pouch lies the source of life, the nipple. Is nature giving us a clue about the origin of BBL? The joey follows the hairs; does BBL take the same path?

Surprisingly for the Hair-Causes-BBL Theory, 3% with "no hair" or "very little hair" also had BBL. Perhaps these people with very small amounts of belly hair wore tight clothes, which helped carry the lint towards the belly button. Once it fell into the belly button, it wouldn't easily come out again. But perhaps there are some other factors involved . . .

Do you have a snail trail? - About 80% of people who have BBL also have a Snail Trail of hair leading up from their pubic hair to their belly button.

Degree of snail trail hairiness - In general, women have pubic hair that looks like an inverted pyramid, or a map of Tasmania, with a sharp cut-off at the top. In general, men have pubic hair with a tapering tail of hair reaching up towards the belly button. However, there is an overlap between the belly hair of men and women - some men have no Snail Trail at all, and some women have a small Snail Trail. Most of the people who did have a Snail Trail had only a moderate one. Our results are a little confusing. It seems that if you have too much belly hair, or too little belly hair, this somehow inhibits the movement of BBL into the belly button. Perhaps a thickly forested abdomen traps the BBL, while an almost bald abdomen doesn't provide enough forward traction.

Innie vs outies -
Your normal belly button is concave, with an attractive upper hood. The base of the belly button usually joins onto the muscle wall of the abdomen. Around the belly button there is subcutaneous fat. In the "outie", there is a protuberant mass of subcutaneous scar tissue between the bottom of the belly button and the muscle wall of the abdomen. This scar turns the concave "innie" into a convex "outie".

Innie/Outie? - About 96% of those with BBL have an innie belly button. Unfortunately, we don't know the ratio of innies and outies in the general population.

So we really don't know how to interpret this 96% figure.

Describe your build - There was no real correlation between BBL and a person's overall build.

Skin colour - There was a slight correlation between skin colour and BBL colour. People with darker skin tones had darker lint. People with lighter skin tones had lightercoloured lint. However, the correlation is so small that it is probably within experimental error.

Skin type - There was no real correlation between skin type and BBL. About 13.5% said they had dry skin, 70% had "normal" skin, and 15.9% had oily skin.

Do you have a navel ring? - Of the people who have BBL, 92% did not have a navel ring, and 8% did.

There were many fascinating insights in the 'any-other-comments' section from people who had a navel ring. Many of them wrote that they did have BBL prior to getting the navel ring. But once the navel ring was installed, the BBL would suddenly either be dramatically reduced, or totally disappear. It seems to us that BBL was originally transferred into the navel by the Snail Trail, or by friction between the clothing and the belly. The presence of the navel ring might act like a centre pole on a circus tent, and keep the clothing from touching the skin around the navel. So the BBL wouldn't get carried over that last little section to the belly button.

What colour is your bellybutton lint and is it related to your clothing colour? - About 37% of people with BBL said that the colour of their BBL was related to the colour of their clothing. About half of these people had blue BBL. Most people wear various shades of blue. But we really can't explain why some people consistently have BBL in a colour that is not present in their clothing.

Do you wash your clothes in a top-loader or a front-loader? - There is a fundamental difference in how top-loaders and front-loaders treat your clothes. A Choice magazine survey showed that in general, a top-loading machine can either be gentle, or can remove a lot of dirt from the clothes - but it can't do both at the same time. Only a front-loading washing machine can be both gentle and thorough. About 80% of people used a toploading machine, 16% used a frontloader, and about 3% said they didn't know.

Animals and bellybuttons - All mammals have belly buttons. However, in some dogs and cats, they're a little hard to see because they've healed well and they are covered with hair.
More bellybutton facts

Again, we don't know what the percentages are of the different types of washing machines in the general community - so we can't really interpret these results. However, Dr Karl has heard many anecdotes that when people have changed from a top-loader to a front-loader, the production of BBL drops dramatically. A typical story is that of a Perth taxi driver. He told Dr Karl that while he was travelling around Australia for 18 months, and using fairly rough top-loading machines in caravan parks, he had continuous BBL. As soon as he settled in Perth and bought his own front-loading machine, his production of BBL dropped to zero. Presumably, a nongentle, top-loading washing machine will loosen up the fibres in your clothing and make them liable to come loose and travel to your belly button.

Did you undertake the hair-free highway experiement? If yes, did you notice a decrease in belly button lint? - 182 people took part in the Hair-Free Highway Experiment. 40% noticed a decrease in BBL levels. 24% did not notice any difference, and 35% didn't know. The 35% unknowns is such a huge percentage that we are not quite sure how to analyse this component of the experiment. Anecdotally, it seems as though the Snail Trail does have something to do with BBL levels. We need further research.

Any other comments on belly button lint? - About two-thirds of the respondents actually added some comments - you can read them in our quotes section.