Sunday, June 16, 2019

The Boy who Cried Wolf: A Bayesian Drama in One Act


The story of the boy who cried wolf too many times is a good way to illustrate our attitude toward the people who try to warn us about dangers ahead. Be it about a wolf or about climate change, the result is always the same: prophets of doom are not believed (and, sometimes, they are hanged). Here is a version of the story of the boy and the wolf told using Bayesian statistics where I assume, unlike in Aesop's version, that the boy was simply trying to do his best (if you are not familiar with the Bayesian approach, try this link where the story is very well explained). This post, anyway, doesn't pretend to use the Bayesian theory in its full version, it is a "montypythonesque" story to illustrate how politicians and the public alike can't understand statistics. (Image from the witch scene in the Monty Python "Holy Grail" movie)


The Boy who Cried Wolf: A Bayesian Drama in one act


Characters


The Villagers
The Village Chief
The Village Master Statistician
The Boy



Village Chief: Fellow villagers, we have collected here today to discuss about the boy who acts as a lookout for wolves in order to protect our sheep. I know that several of you have been complaining because the boy has been crying wolf at night several times this year, and every time we woke up and went to the village fence to protect our sheep armed with clubs and pitchforks and carrying lighted torches. But we seem to have a problem with that.

Villager: Yeah, yeah, we go there and there is no wolf to be seen!

Another villager: The boy calls us for nothing!

Another villager: We must hang him!

Village chief. CALM DOWN, fellow villagers. You know that a few times we did see a creature that seemed to be a wolf in the light of our torches – although we couldn't be sure.

Villager: It was not a wolf. It was a black sheep!

Another villager: It was a wild boar!

Another villager: Nothing like that. It was just a shadow!

Another villager. The boy works for the wolf! He does!

Other villagers: Hang the boy, hang the boy!!

Village chief. Fellow villagers, PLEASE, be quiet. It is true that sometimes we didn’t see anything: no wolf appearing the light of our torches. And, worse than that, a few times the wolf came, snatched away a sheep or two, and the boy didn't alert us in advance.

Villager: The boy is playing tricks with us!

Another Villager: Yeah, the boy just enjoys seeing us running!

Another Villager. There are no wolves when he calls! The boy is cheating us.

More villagers. Hang him high! Hang him! Yeah! Yeah!

Village Chief. Calm down, fellow villagers, CALM DOWN! This is not the way to discuss this serious matter because it may well be that the boy is doing his best, but the night is dark and the wolf is cunning, so it is not easy to be the village lookout . . .

Villagers, Hang him, hang him!

Other villagers. Yeah, he is paid by the wolf. Hang him!

Village Chief. And I say BE QUIET! Because I called the village’s Master Statistician to help us and he will tell us whether the boy is doing us a good service according to his Art of which every one of us knows he is a good and respected practitioner.


– Enters the Village Statistician –


Village Statistician. Fellow villagers, lend me your ear because I heard your plight and I am a master of an Art that can help you in this difficult matter.

Villagers: Yeah, let’s listen to the statistician, let’s listen to him!


Statistician: Fellow villagers, the problem you have here is that you don’t know for sure whether there is a wolf or not when the boy calls. And, of course, you don’t like to rush to the fence at night and find that there is no wolf there – at least no wolf that you can see. But thanks to my Art, I will be able to tell you things that that you wouldn’t otherwise know. And this Art is the work of a great master statistician whose name is Bayes and who is respected for this all over the world.

Villager: Yes, yes, master, tell us!

Another Villager: Yeah, master. We trust you. Tell us!

Statistician. Fellow villagers, first of all, let me summarize the situation. If there is no alert before the wolf attacks, the villagers usually arrive too late to save their sheep: the wolf is quick and cunning and he is able to snatch a sheep or two and run away. Hence, we need to be alerted well in advance. That's why the boy keeps watch of the village fence.

Villagers. Yeah, master, yeah. What you say is right.

Statistician. Now, being the village statistician, I keep a record of the wolf attacks and this record I have kept for the years when there was no lookout and so this number tells us how many times the wolf comes, on the average. And I can tell you, fellow villagers, that during the past years there was a chance of a little less than 3% per day of a wolf attack.

Villager. Yes, Master, yes. That’s great.


Another Villager. But what does that mean, Master?

Statisticians. It means, fellow villagers, that the wolf comes about 10 times per year.

Villager. Yeah, yeah, master. We understand that.

Statistician. Very good, fellow villagers. And we shall call that number, 3%, the PRIOR, according to my Art as taught by master Bayes. Remember that carefully!

Villagers: yeah, yeah, master. We remember that!

Statistician. Now, I need the boy who acts as a lookout to help me. Come in, boy!


- Enters the boy -


Boy: Master, I am here at your bidding.

Villagers. Hang him, hang him!

Other villagers. Yeah, yeah, hang him!

Village chief. BE QUIET, I say.

Statistician. Boy, let me ask you, how many times did you see the wolf coming this year?

Boy. Master, Every time I thought I saw a wolf I marked a sign with my knife on the bark of the tree on which I stand at night. And I counted these signs, and there were 20 of them.

Statistician. Very good, my boy. So, dividing this number by the number of days in a year, we see that every day there is a chance of 6% that the boy calls. Therefore, according to my Art, we call this number the EVIDENCE.

Villagers. Master, does that mean we should hang the boy?

Village Chief. QUIET, I say.

Statistician. Fellow villagers, the art of master Bayes is going to help you, but I need some more work. Now I need to know how many times the wolf came unannounced this year. That is, the boy didn’t call, but the wolf came. And you told me that it appeared 4 times. With that, I can calculate the LIKELIHOOD according to my Art. And this likelihood is the number of times the wolf is announced when it comes, divided by the number of times when the beast comes, no matter whether unannounced or announced. So, my data tell me that the wolf comes 10 times per year, whereas it came unannounced 4 times this year. It means its venue was correctly announced six times. In this case, the likelihood will be 6/10, which is 0.6.

Villager. Yeah, yeah, that’s right. That’s right. It means we should hang the boy, right?

Another villager.  Hang the boy! Hang him! The Wolf will be very unhappy!!

Village chief. QUIET, fellow villagers. Statistician, what can you tell to us, now?

Statistician. (takes out a charcoal stick and rolls open a tanned sheepskin, starting to write on it). I can now use the formula that the Master of the Art, the much esteemed Thomas Bayes developed. So, the formula tells me that I have to multiply the PRIOR by the LIKELIHOOD and divide by the EVIDENCE. And the final result is .03/.06*.60= 0.3 or 30%


--- silence  --


Villager. Shouldn’t we just hang the boy?

Village Chief. KEEP QUIET. Master Statistician, please explain to us what you just said.

Statistician. Fellow villagers, it means that when the boy calls, the wolf will be there once every three times, approximately.

Village Chief: But that means, Master, that many times we rush to the fence for nothing, right?

Statistician: That's true. Two times out of three.

Villagers. It is what we said! The Boy is tricking us

Other Villagers. Hang the boy, hang him!

Other Villagers. Yeah, yeah. The boy works for the wolf!

Other villagers: Yeah, yeah, let's hang him!!


- The villagers take hold of the boy and take him away. The boy screams.


Statistician. Chief, this is not good. You should explain to the people of the village that they shouldn't behave like the members of the evil sect we call the Frequentists. Without the boy, every day the probability for the wolf to be there would be only 3%. With the boy, you have 30% when he calls. And it is much better.

Village Chief. Dear Statistician, I think the villagers are right. The boy should be hanged: he might be working for the wolf, after all!


– Exeunt –



NOTE 

The Bayesian analysis is a powerful tool and it can be used to study climate change. It is especially powerful when it is used to correlate the rise of carbon dioxide with temperature increases, as it is done, for instance, in this paper. Just as an example, think of the concept of abrupt climate change and the correlated mass extinctions. We know that there have been five major mass extinctions during the past 500 million years or so. Then, from a "frequentist" viewpoint, you could say that the probability that a new mass extinction during the next century has a probability of about 100/100,000,000, that is one in a million and you would feel safe. But if you take into account the correlation with the CO2 rise during the mass extinctions, then the Bayesian analysis tells you a completely different story when you compare with the current CO2 spike. I think the data available are not good enough so far for a complete quantitative analysis, but that gives you some idea of the power of the method. The problem is that neither the public nor politicians understand it.


Sunday, June 9, 2019

"The Seneca Strategy" -- Asking for Suggestions from my Readers





About Amelia the Amoeba, she is a pedigreed Naegleria Fowleri, a species known for her habit of eating human brains - an interesting case of a Seneca Collapse for the owner of the brain. But Amelia is a good girl and she won't do that to you if you are nice to her.



My second book on the concept of "Seneca Collapse" (or Cliff, or Ruin, or the like) is nearly completed and it should be available from Springer before the end of the year. It is a sequel to my first book, "The Seneca Effect", but this second one is thought as more easily readable "trade" book. It will be sold at a reasonable price, unlike the first one that was supposed to be a specialized, scientific book.

You see above a first attempt at a title and a cover for this book. Of course, the publisher will devise a better cover illustration, but the real issue is the title, still provisional. I used "The Seneca Strategy" as a title because the book focuses on how to deal with collapses rather than on the physics of collapses. It proposes a strategy that's based on the Stoic view of the world revisited under the lens of system dynamics. It is the idea that you don't try to force systems to do what you want them to do, a concept that Jay Forrester termed "pushing the levers in the wrong direction."

But, as it stands, the title is no good. My editor told me that, "“collapse” is not a friendly, or familiar, word to most readers. It seems to apply only to extreme events that don’t affect most people. " That is, people won't understand what the book is about. I think he is correct and that I need a better title -- a title that explains what's inside the book.

So, dear readers, could you focus your creative skills on this task and suggest a few titles for me? I think the title should contain the words "collapse" and "Seneca," but then there are many possibilities, for instance, I am toying with "Paths to Ruin" but creativity often consists in trying many different ideas and I am sure many of you could suggest something good. Hoping that not all of my readers are bots, I'll sure appreciate your efforts! (Amelia will also be grateful)

Here is the index of the book, to give you some idea of what it is about.


  1. Table of Contents
1. Preface 4
1.1 A quick glossary of the terms you’ll find in this book. 5
2. Summary: Six Things You Should Know About Collapse 6
3. Plan of the Book (not necessarily to be published) 8
4. Collapse: An Introduction 9
5. Models of Collapse 14
5.2 The Limits of Models. Nightfall on Lagash 23
5.3 Why Models are not Believed: The Croesus Syndrome 29
6. The Science of Collapse 36
6.1 Complex Systems: The Goddess’ Wrath 36
6.2 The Power of Networks: The Ghost in the Shell 42
6.3 Living and Dying in a Complex Universe. The Story of Amelia the Amoeba. 52
7. The Practice of Collapse 76
7.1 The Collapse of Engineered Structures: For Dust you are and to Dust you Will Return 76
7.2 Financial Collapses: Blockbuster goes bust. 84
7.3 Natural Disasters: Florence’s Great Flood 94
7.4 Mineral Collapses: The Coming Oil Crisis? 103
7.5 The Seneca Cliff and Human Violence: Fatal Quarrels. 111
7.6 Famines, Epidemics, and Depopulation: The Zombie Apocalypse 117
7.7 The Big One: Societal Collapse 125
7.8 Apocalypse: the collapse of the Earth’s ecosystem 132
8. Strategies for Managing Collapse 138
8.1 Technological Progress against Collapse. The Cold Fusion Miracle that Wasn’t. 138
8.2 Avoiding Overexploitation. Drill, Baby, Drill! 148
8.3 Leadership Against Collapse: The Last Roman Empress. 155
8.4 Collapse as a Weapon: The Iago Strategy 164
8.5 Deception as a Strategy: the Camper’s Dilemma 174
8.6 Life After Collapse: The Seneca Rebound 181
9. Conclusion: The Seneca Strategy 189
11. Acknowledgment 195
12. REFERENCES 196








Tuesday, June 4, 2019

The Second Babel Tower: Symphonic Music and the Collapse of the European Cultural Unity


This is Europe


This is not Europe




This is a reflection on how the breakdown of the Medieval cultural unity in Europe resulted in many different effects, from witch hunts to classical music. It came to me from putting together various elements of various talks heard at the excellent meeting "Colloqui di Martina Franca" held in Apulia in May 2019. H/t Boian Videnoff and Giovanni Semeraro.




The study of the patterns of world conflicts leads to fascinating results, showing the statistical patterns that make wars a sort of natural phenomenon, beyond human control. But there is something in the data that defies statistical analysis. Look at this figure, showing fatalities normalized to the world's population: (data from Martelloni, Di Patti and Bardi, 2019)


Note how there seem to exist two sections in this graph: one is relatively quiet, from 1400 to ca. 1600, the other is stormy: a series of terrible wars starting with the 30-years war that remained the largest in history, in relative terms, until it was surpassed by the 2nd world war. And not only the age of wars started in the mid-17th century, it was also the start of a wave of violence against women: tens of thousands of them, typically poor and illiterate, were tortured and burned alive under the accusation of witchcraft. The data are strongly euro-centered, so there was some kind of a radical change in Europe around mid-1600s. But what was it? And why did it happen?

It is a long story that can be seen in many ways and that shows many facets. In this post, I thought I could focus on how the great transition of the mid 17th century was reflected in a specific area of European culture: music. When Europe lost Latin as a shared communication tool, it was a new Babel Tower: Europeans couldn't understand each other any longer except within the boundaries of their national states. Not surprisingly, people who don't understand each other tend to resort to war to sort out conflicts. But Europeans also tried to replace Latin with some non-verbal tools: one was music. It is a long story that needs to be told from the beginning.

Did you ever realize how strange is the existence of symphonic (or "classical") music? Purely instrumental music is very rare in history and in geographical regions other than Western Europe and its cultural offspring. In most cases, music is purely vocal and instruments are only an optional tool to accompany and enhance the human voice. Instrumental music is even considered sinful in itself by many Islamic scholars.

That's indeed the rule for what we know about the history of European Music. During the Middle Ages, the main genre was Gregorian music: purely vocal. Note how a Gregorian chant is focused on words: listeners are supposed to understand what's being said. Then, the Renaissance came and it was the age of polyphony where the harmony takes precedence -- it is beautiful, but words overlap and the sense of the text is soon lost.

The trend toward polyphony continued in the 1700s when instrumental music became more and more common. It became the norm during the 1800s with the golden age of classical music: Beethoven, Brahms, Schubert, and many others. Symphonic music continued to be popular well in the 1900s, think of George Gershwin's "Rhapsody in Blue" (1924). But, in time, it faded away. Today, orchestral symphonies are still written and performed, but they are not anymore a popular form of art. We seem to have gone back to a kind of music that focuses on voice and words: the rap. (for a nice version of a rap relevant to the title of this blog and also sung by a physicist, see this link)

What generated this cycle? Mainly, it was the Babel of languages that Europe had become that pushed Europeans to try to develop new forms of communication. Music is a language, not the same kind of language that uses words, it is a tool used mainly to convey emotions rather than facts and data. It can be used to create social bonds or to intimidate an adversary (in the latter case, it is termed AVID - audio-visual intimidating display).

Actually, as argued by Joseph Jordania, music may be the origin of language and polyphonic music is much older than the monophonic kind we are used to, nowadays. Gradually, with the development of word-based languages, monophonic music became prevalent. But, in some peculiar conditions, when the word-based communication breaks down, the Babel Tower effect takes place: to understand each other we must revert to different tools. Polyphonic music, classical symphonies, the haka, they are all forms of emotion-based forms of communication. They are not necessarily inferior to the word-based kind, they bypass words to reach directly the heart of people. And there is no doubt that the haka was conceived as a way to reduce violence as much as possible. But music can't convey the same richness of meaning that words can provide.

So, Beethoven's third symphony is commonly termed the "Heroic." It is hard to pin down what exactly that means, but most people would agree that there is something heroic in that music. There is no Moon in Beethoven's "moonlight sonata" but somehow the music seems to evoke the moonlight. And Beethoven's fifth symphony is the one perhaps closest to the Maori's haka, even though there is much more in Beethoven's fifth than pure intimidation (that's true also for the haka, which is a sophisticated art form in itself -- not polyphonic, though! H/t Elena Piani) (*).

The evolution of Western European culture makes a lot of sense on the basis of these considerations. The Middle Ages were a period of cultural unity in Western Europe. Latin was gradually lost with the Renaissance and this generated new forms of music-based communication. In time, these forms were made unnecessary by the triumph of English as worldwide lingua franca. It may be the reason for the relative lull in the frequency and the intensity of wars during the past 50 years or so, as noted by Steven Pinker in his "The Better Angels of Our Nature:" (2011). It is also the reason for the age of the Rap, in which we are living.

Today, the evolution continues. Maybe English itself will be made obsolete by tools such as Google translate. Maybe we'll use only emojis :-). Maybe we'll develop new methods of communication which, today, we can't even imagine. But there remains a basic fascination in singing together, especially for polyphonic music. It is an art that has been mostly abandoned, today, except in some special religious contexts. But it won't die so easily and if you ever had a chance to sing in a polyphonic choir you understand what I mean. It is music that bypasses your brain to touch your heart. An example, below, the Benedictus as performed by singers of the Taizé Community.





This post was generated by a meeting in Martina Franca that I attended last week. I heard first a talk by the AI scientist Giovanni Semeraro. It made me think of how words are the fundamental unit of communication in languages, but also made me wonder if it were possible to communicate without words. Then, it was the turn of Boian Videnoff's talk on complexity in music and - bang! - a hit of serendipity. European wars, symphonic music, polyphonic music, and Gregorian chants, everything clicked together -- there was a meaning in the gradual evolution of different musical genres! A final point: why did Europe lose Latin? I think there are reasons, but that's a discussion for another post. 


Upon rethinking the matter over, I think the haka IS polyphonic. It is an integrated mix of words, gestures, facial expressions, and dance. A stunningly sophisticated art form. 

 

Who

Ugo Bardi is a member of the Club of Rome and the author of "Extracted: how the quest for mineral resources is plundering the Planet" (Chelsea Green 2014). His most recent book is "The Seneca Effect" (Springer 2017)