Informational cascades

Skógafoss, Iceland

Sometimes we make our own decisions; sometimes we follow a decision taken by someone else. There can be good reasons for following another person, but if an agent makes a decision based on what another person does without regard to his own private information, just because s/he thinks that what the other decides must be right, and if other agents do so as well, then we are in an informational cascade (or information cascade).
Let’s take an example (from Noise by Daniel Kahneman et al. pp. 100-103). Ten people must decide whom to hire for an important position. There are three candidates and the members of the group announce their views in sequence. Arthur speaks first and sees Thomas as the best choice. Then Barbara speaks. She is not sure that Thomas is the best choice but is unsure who is. She trusts Arthur and so she chooses Thomas as well. Next it’s Charles’s turn. He thinks that Thomas is not a good candidate but that Julie is. Nevertheless, he also chooses Thomas, not because he feels under pressure and doesn’t have the courage to give a different opinion, but because he thinks that Arthur and Barbara have good reasons for their choices. Unless David, person 4, has strong reasons against the choice of Thomas, probably he’ll follow the others before him. If so, then we are in a cascade. Etc.
Informational cascades are also a much happening economic phenomenon. Here is an example, taken from the Investopedia: Someone might think that a certain financial pundit has more knowledge and information than he himself has. Therefore, he imitates the pundit’s stock picks. A neighbour observes him boasting about his stock picks, and she also picks the same stocks. Another neighbour notices that both people chose the same stocks and assumes that those stocks must be good picks, simply because more than one person has picked them. An informational cascade has begun, and all of the participants have very little information to back up their decision-making.
Informational cascades also happen in daily life. A group of friends wants to go out to eat together. Each one of the friends has his or her preferences where to go. One proposes a restaurant and the others agree.
There are several conditions that make that we can speak of an informational cascade (see here and here):
- There is a decision to be made; agents make the decision sequentially, and each agent can observe the choices made by those who acted earlier.
- A limited action space exists (e.g. an adopt/reject decision).
- Agents make decisions rationally based on the – usually limited – information they have.
- Agents do not have access to the private information of others.
Note that each decision is based on the information the agent has and that the agent is not deciding under group pressure. Maybe s/he has some doubts about the group decision, but in fact s/he trusts that the others are right and actually the agent lacks good reasons that they are not. Otherwise s/he would have said so. From this point of view, it’s not necessarily irrational for the later deciding agents to follow the decision others have already expressed. If you are not really sure what to do, it may be smart to follow the others.
Nevertheless, an informational cascade is not unproblematic. First, if another agent would have expressed his or her choice first, another decision might have been taken by the group; or, second, if the first agent also was not really sure what to decide, s/he might have taken another decision. So the final decision can be the result of the arbitrary decision of the person speaking first. Third, people tend to ignore that other agents are in the same informational cascade and are not deciding independently. They may think that there is some crowd wisdom, while in fact they follow the initial view of the first decider. Fourth, the decision of the first decider may be completely wrong with possible nasty consequences if everybody follows this person.
Although the decision procedure just sketched is far from uncommon, it is risky. Note that it is a procedure that is applied in a situation in which the agents are not really sure what to do and that their decisions are sequentially taken and known to everybody. In such a situation the final decision tends to be arbitrary and can even have fatal consequences. Market leaders can be the source of much financial if not economic harm, if others mistakenly think that they have the right information and therefore follow them. It is also possible that a decider is not reliable, and a non-reliable agent who wants to manipulate a decision to his or her advantage can try to be the one who decides first, hoping that others will follow. Or, a committee can take the wrong decision, such as hiring the wrong person, if it uses a sequential decision procedure and gets into a cascade. Or friends can go to the wrong restaurant. One solution to avoid an informational cascade is to vote by secret ballot, but this doesn’t work in a financial market. Then we come to such solutions as think twice before you act. However, informational cascades can also have positive effects. The fall of the German Democratic Republic in 1989 was the result of initially small protests in Leipzig that gradually grew because more and more people decided to join, just because others did. People followed other people without really knowing whether to do so was right, in the sense that the protests could have led to a massacre as well. Informational cascades are fragile phenomena.

Sources: The references quoted in the text.

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The average expert is roughly as accurate as a dart-throwing chimpanzee

Philip E. Tetlock (1954-)

Why I become tired, when I write a blog

I often make a bike ride. When I ride with an easy speed and the distance is not long, afterwards I feel relaxed. When I ride a long distance with a fast speed, I feel tired at the end. We think it’s normal that making a great physical effort makes you tired. It is because your muscles become filled with lactic acid, which must be cleared up in order to feel fresh and rested again.
Once a week I write a blog. When I have finished it, I feel tired, for usually it is a hard job. So, afterwards I want to relax, for instance by making an easy bike ride. But why do I feel tired? Most of the time I sat down in my chair and only my fingers moved a little bit in order to type my blog and to do a few internet searches. Nonetheless, I feel tired. Even more, mentally tired people who must take decisions, like chess players, are going to make mistakes, just because they are tired; types of mistakes they wouldn’t make with a fresh mind. How come?
Several explanations have been given why thinking makes you tired. Actually, you are not tired but bored, some say. You want to do something else and so your brain tells you that you are tired. Or, another explanation, the deeper you go into a problem, the more complicated it seems, so that’s why you are going to make mistakes. It’s a way to explain mistakes made by chess players. At the beginning of a game they can use their routine, but later on they must rely on their insight and then they can fail. Other explanations for mental fatigue have been suggested as well. However, a group of French researchers didn’t find the existing explanations very satisfying, so they developed their own approach. Let’s look in the brain and see what happens if people get mentally tired, they thought, and they developed relevant tests. If you make a light physical or mental effort, you don’t become tired, but you do if your effort is hard. Maybe, you become mentally tired because some stuff piles up in your brain when you are thinking, which makes that you feel fatigue; just as in the case of a physical effort like cycling. Therefore, these researchers developed a light and a difficult version of the same mental task and watched the brains of their test persons and looked what happened; moreover, they looked at the reaction of the pupils. The task chosen lasted several hours. For watching into the brains of the test persons, they used an MRS scanner (MRS = magnetic resonance spectroscopy). With such a scanner you can see what happens with the blood currents and the chemistry in the brain, when the test person is active or passive.
What did they find? Indeed, becoming tired when doing a mental task is not a mental affaire, but it is as physical as becoming tired in your legs when cycling. There were clear differences between the test persons that did a light task (and didn’t become tired) and those who did a hard task (which made them tired). The researchers saw signs of fatigue, including reduced pupil dilation, only in the latter group. Those in that group also showed in their choices a shift toward options proposing rewards at short delay with little effort. But most important, they had higher levels of glutamate in synapses of the brain’s prefrontal cortex. The prefrontal cortex is the part of the brain in the forehead where decisions are taken. These results made the researchers conclude, together with earlier evidence, that it is likely that glutamate accumulation makes further activation of the prefrontal cortex more costly, such that cognitive control is more difficult after a mentally tough workday. In other words, glutamate poisons your brain and that’s why it disturbs your thinking. Only after it has been cleared up, you feel fresh and rested again. Actually, there is not much difference between feeling physical and mental fatigue. The difference is in the details and the solution is also the same, and actually not really surprising: take a rest or take a nap. And if you are really tired, go to bed. The conclusion feels like kicking open an open door. Nevertheless, it isn’t. People often think: I am tired, the task must be done. And they go on till the job has finished. Maybe, they even think that feeling mentally tired is an illusion, and anyway that it’s not that bad (think of doctors, at the end of a workday). Maybe, there are other reasons to go on, but from a psychological point of view it’s a bad idea: It’s almost sure that mistakes will be made. Fatigue is an objective real phenomenon with a physical base. So, avoid making important decisions when you are tired.
The knowledge from this study (and from future research) can also help to tackle mental problems. For example, the researchers say, monitoring of prefrontal metabolites could help to detect severe mental fatigue. Such an ability may help adjust work agendas to avoid burnout. In future studies, the researchers hope to learn why the prefrontal cortex seems especially susceptible to glutamate accumulation and fatigue. They’re also curious to learn whether the same markers of fatigue in the brain may predict recovery from health conditions, such as depression or cancer.
So, now you understand why I am tired, when I have written a blog.

Sources
- “Why thinking hard makes you tired”, Cell Press (here and there above literally quoted or paraphrased)
- Antonius Wiehler et al. “A neuro-metabolic account of why daylong cognitive work alters the control of economic decisions”

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The ego is the product of the development of the personality and not - as many psychologists assume - the producer of the personality.

Gerhard Roth (1942-)

Killed in action, 18 years young

I assume that you have guessed from my mini-blog about Wilfred Owen that I have been in France recently and that I have visited his grave. I published this short mini-blog because I had no time to write a real blog but didn’t want you to be too long without one.
In fact, I didn’t go to France for visiting Owen’s grave, for when I left home, I hadn’t realized that it was not far from where I had planned to stay. However, my trip had to do with the cause Owen had died for, for I went to the battlefields east of Reims, in the north of France. The region around Reims is called Champagne. It is known by most people for its wine, but those interested in the First World War know that there has been heavy fighting in the region, especially in 1915. These fights are known as the First and Second Battles of Champagne. I have a website with photos of World War One monuments and just photos related to these battles yet failed there; so a good reason to go there this summer.
As everywhere along the former front line in Northern France and Belgium, also the region east of Reims is full of war monuments and traces of World War One. Most important is the War Memorial for the Armies of Champagne near Sainte-Marie-à-Py, but, as everywhere along the former Western Front, most striking is the big number of war cemeteries. Only in these two battles more than 100,000 French soldiers plus the same number of German soldiers died. Some cemeteries are only for French soldiers, other ones are for German soldiers and again other ones are mixed in the sense that they have sections for both nationalities. Some soldiers got individual graves and other soldiers have been buried in mass graves, especially those killed in the beginning of the war. Most soldiers are known by name but some have a stone or cross with the inscription that an unknown soldier lies there. When I am in the former war zone, I always visit several war cemeteries. I walk along the crosses and stones, read some of the names, when they died and how old they were. Most were in their twenties. Sometimes I read also the book with names which is always there and sometimes I also sign the guestbook.
In the meantime, I had discovered that Wilfred Owen had been buried not far from where we stayed, but more to the north, in Ors in the Nord Department. So after having been a week in Champagne my wife and I decided to spend there the last days of our trip and to visit Owen’s grave.
Wilfred Owen has been buried in the British section of the Ors Communal Cemetery. He was killed while he was encouraging his men when they tried to cross the Oise-Sambre Canal. Owen had previously been treated for “shell shock” in a psychiatric hospital and needn’t to go back to war, but he chose to do so since he felt guilty because his comrades were fighting and run the risk to be killed, while he was safe in England. Owen was killed on the 4th November 1918, one week before the war ended.
It was easy to find his grave in the Ors Communal Cemetery, since there had been put a few little crosses in front of the stone by admirers. It was in the last row of the British section, third from the left. Owen was 25 years old when killed, so he was quite young. On a gravestone more to the right, I read the name of a captain who died 42 years old. Then I read the gravestone just left of Owen’s final rest-place: 63554 Private W.E. Duckworth, Lancashire Fusiliers, 4th November 1918 Age 18. I got a shock. Of course I know, that such young people had been sent to this war and had been killed there, but nevertheless I was shocked. Owen was with his 25 years already very young when he was killed, but 18 years? This private was actually yet a child, when he died. 18 years old was so young! Who was this man; who was this child? A quick internet search taught me that this private was William Edward Duckworth, son of William and Sarah Duckworth, of 99, Warwick Rd., Carlisle. I didn’t find his date of birth, but since William Edward was yet so young, I assume that he lived yet with his parents when he left for war and so that he was also from Carlisle. But then the question remains: Why did he go to war? Of course, I know that it happened much then that such young boys went to war and that many went by their own choice. But even then, who has sent such young boys, children yet, to the battlefields?
But not only then, still today children are sent to war. The problem of child soldiers is a widespread evil. But also if a soldier is “already” 18 years old and officially no child any longer, in many respects he still is. Mentally, 18-years-olds still aren’t fully grown-up. And do they know enough about the world to bear the responsibility of a soldier in action and are they mature enough to be exposed to war risks? And what will be the consequences for a society that sees its young people lost and so will see a literally lost generation?
But times have not changed and times are not changing. Yet-nearly-children are still sent to war, like in Ukraine – by both sides – and elsewhere in the world. Still children and nearly-children are killed in action, physically or mentally.

Random quote
War broke: and now the Winter of the world
With perishing great darkness closes in.

Wilfred Owen (1893-1918) 

Wilfred Owen

Recently I was in Ors in Northern France, where the famous British war Poet Wilfred Owen (1893-1918) was killed in action, on 4 November 1918, one week before the end of the First World War. I visited his grave there on the Communal Cemetery, where on request of his mother these words had been written on the stone:

“Shall Life renew these bodies? Of a truth
All death will he annul”

At first sight, these words, which are from a poem by Owen, make you think that he believed in a life after death, but the poem itself suggests just the opposite, since the full second sentence is:
“All death will he annul, all tears assuage?” Just the question mark shows that Owen probably did not believe in an after-life. Why then did his mother select these words?

Here is the complete poem, which is still worth to read in view of the Russian Ukraine War and all other wars that are still waging in this world:

The End
After the blast of lightning from the east,
The flourish of loud clouds, the Chariot throne,
After the drums of time have rolled and ceased
And from the bronze west long retreat is blown,

Shall Life renew these bodies? Of a truth
All death will he annul, all tears assuage?
Or fill these void veins full again with youth
And wash with an immortal water age?

When I do ask white Age, he saith not so,—
“My head hangs weighted with snow.”
And when I hearken to the Earth she saith
“My fiery heart sinks aching. It is death.
Mine ancient scars shall not be glorified
Nor my titanic tears the seas be dried.”