What to do with our beliefs?

The widely used approach to quantify our beliefs and their relation to observations is Bayesian statistics. For example, I can belive that the average height of men in China is 160 cm, most of the men being between 150 and 170 cm. Then I go to China and start measuring men there. I look at my results and see that they are distributed not exactly as in my prior belief. How should I update my belief? A clear non-mathematical introduction on Bayesian statistics explains the idea of the method:


Probability is relative


At Aeon, Nevin Climenhaga makes some interesting points about probability.  After describing different interpretations of probability, one involving the frequency with which an event will occur, another involving its propensity to occur, and a third involving our confidence it will occur, he describes how, given a set of identical facts, each of these interpretations can lead to different numbers for the probability.  He also describes how each interpretation has its problems.

He then proposes what he calls the “degree of support” interpretation.  This recognizes that probabilities are relative to the information we consider.  That is, when we express a probability of X, we are expressing that probability in relation to some set of data.  If we take away or add new data, the probability will change.

This largely matches my own intuition of probability, that it is always (or almost always) relative to a certain perspective, to a particular…

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There Is Only Weak Evidence That Mirror Neurons Underlie Human Empathy – New Review And Meta-Analysis — Research Digest

By Christian Jarrett. After nearly two decades of research, our understanding of the neural basis of empathy, and especially the role played by mirror neurons, remains far from complete.

via There Is Only Weak Evidence That Mirror Neurons Underlie Human Empathy – New Review And Meta-Analysis — Research Digest

Popular science may be both fruitful and dangerous

thermometer on medical pills
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Popular science is a well-established way of spreading the scientific culture and simplifying the meaning, results and consequences of scientific works. Often appearing to be a fruitful portal, popular science allows the general public to get an inkling of what is going on in the scientific world. In addition, it is also a good method of “translating” science for non-scientific experts working in the field of the humanities – for example, philosophers.  Indeed, writing popular science articles can be seen as equivalent to translating texts between languages of different ethnic groups. However, as with every translation effort, attention has to be paid to the fact that translation is an imperfect process. It gives only a general picture. Moreover, for a successful translation from one language to another, we need not only an expert’s understanding of both languages but also someone with expertise in translation itself.

Likewise, it is possible for non-scientific people or students of the humanities to find through popular science a way to build a vision of scientific knowledge. Unfortunately, on many occasions, I have happened to read stories that have been badly popularized, where the author misunderstood the scientific study and, in the translation, has misled the general public and also non-expert scholars. Moreover, a lack of global vision and of deep knowledge can inevitably lead to erroneous interpretations and the consequences could be disastrous.

To avoid the pseudo-knowledge of non-experts, scientific knowledge should be popularized by experts in the field who have at the same time mastered a good method of explaining it to the general public. Indeed, popular science is a powerful and useful tool for scientists to achieve these important goals (*):

  • To translate complex scientific works for people far from the scientific field.
  • To disentangle some misunderstood concepts or ideas used by some pseudoscientific books or magazines.
  • To explain to the general public that some ideas are not really scientific ones and provide ways and tools in order for them to comprehend the unadulterated reality of science.

Thus, having a large population getting a clear picture of scientific knowledge will empower citizens able to make reasoned decisions on issues related to, for example, science and the medical field and will prevent society from reverting to the dark ages of history.

Amirouche Sadoun

*Laura Bonetta. 2007. Scientists Enter the Blogosphere. Cell 129, pp. 443-445.

Can philosophy help science?

grayscale photo of man thinking in front of analog wall clock
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Modern scientific breakthroughs have raised many philosophical questions covering several domains, such as mathematics, genetics, quantum physics, artificial intelligence, psychosurgery and cognitive neuroscience. For example, the complexity of the brain, as revealed by the new techniques of imaging and other technology, demonstrates a level of organization that even scientists are only starting to understand and opens an immensely rich field of thought that philosophers are struggling with. Contemporary philosophers, such as Gaston Bachelard, regretted that a lot of philosophers, like Emile Meyerson, did not take much serious consideration of the diversity of scientific knowledge, a necessary step to conceive any philosophy of science. More specifically, Meyerson did not foresee that changes in scientific paradigms would lead to changes in the conception of epistemology itself (*).

Indeed, the considerable development of science, the complexity and richness of its terminology and its myriad concepts in our modern period make it more and more difficult to those who do not have (at least not yet) a scientific background to grasp what happens in several interconnected fields of science. How could a student of philosophy provide the analysis of scientific knowledge (epistemological analysis) without being able to understand at least one of the scientific areas, without being primarily a scientist? How is it possible in this condition to be able to construct and develop a critical analysis of the scientific method, its inferences and logical forms, if one does not have scientific training? It is certainly almost impossible to approach this goal with just a rudimentary scientific knowledge. Would that mean that modern science is destroying the philosophers’ field of thinking and reasoning? Certainly not. In my opinion, the access to the philosophy of science is always possible if one has a minimum of scientific background and an understanding of the basics of scientific methodology and recent advances. Students of philosophy already have a highly charged curriculum, so a good alternative would be for the scientists themselves to try to approach philosophy in search of a deeper or more general understanding of scientific problems and controversies.

Amirouche Sadoun

* Frédéric Fruteau de Laclos. 2008. « Le bergsonisme, point aveugle de la critique bachelardienne du continuisme d’Émile Meyerson ». In Bachelard et Bergson (2008), pp. 109-122. Ed. Presses Universitaires de France.

Fantastic ideas are real

We think that either space and time perception or, for example, face perception are inevitably engrained in the physical laws of our body. These laws seem subjective when perceived from the interoceptive point of view. However, they reflect the same physical laws as in the rest of the universe. Our internal state has the same objectivity as any other event in nature and it needs to be studied to discover physical laws behind it.

Even if we imagine a fantastic object, this imagination is just another phenomenon of nature resulting from objective physical laws in the brain. E.g. if we study water flows in the ocean, a certain flow may seem fantastic or even absurd but it is always based on a set of physical laws. It may seem fantastic only because we do not know yet physical laws behind it. This concerns any observation in nature including our thoughts and internal representations.

Kuzma Strelnikov and Amirouche Sadoun

Energy, information and…the brain


This blog aims to provide a conceptual understanding of physical and philosophical issues for cognitive and other scientists.
I will begin with a general topic, which interests me as neuroscientist – the concepts of energy and its different types. I will avoid the formulas but emphasize their physical content.
Energy is an abstract quantity that is used to describe interactions between different objects and processes. The advantage of the notion of energy is that it permits comparison of totally different processes (e.g. one can compare climbing a hill and boiling a can of water in terms of their energy requirements). Another important advantage of energy notion is that it permits linking totally different processes using the idea of energy transformation between them (e.g. to link energy in a piece of bread with energy needed for the muscles to lift an object).

sliced bread on white surface
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Thus, energy permits obtaining a general idea of something in common between totally different processes or drawing a link between them without going into details of exact interactions and transformations, which are always quite complicated.
For example, one can generally say that energy of glucose is partly transformed to the energy of electric fields in neural cells. This statement is true even if we do not provide any details about the mechanisms of this transformation. Even if we know the principal steps of the transformation, we do not describe it precisely in terms of how atoms and electrons interact with each molecule and between the molecules. Thus, the notion of energy permits following the general mechanism without getting lost in complicated molecular and quantum details at each step.

five bulb lights
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Interactions between objects are usually due to the fact that they are in motion or they have a special position in space. When an object is in motion, it has kinetic energy. When it is in a certain position, which may potentially lead to motion, it has potential energy. For example, different parts of a complex molecule have a certain position with respect to each other that defines the potential energy of the molecule—the potential of its parts to move with respect to each other.
If we hold something in our hand without moving, this object has a potential to fall; thus, it has potential energy due to its position. If we release the object, it falls and acquires kinetic energy due to its movement. In this way, potential energy is transformed into kinetic energy. Importantly, as the two types of energy mutually transform, their sum remains unchanged. The same concerns, for example, gas molecules in a certain closed and isolated container—the total sum of potential and kinetic energies of molecules remains the same.
That is why the term internal energy was proposed, which is the sum of kinetic and potential energies of all molecules in the container under the given conditions. The way to change the internal energy of the container would be to change conditions, e.g. to heat it. Heating would increase internal energy of the container.
Without changing the surroundings, i.e. without putting energy into the system or taking energy from it, the internal energy of the isolated object does not change with time, but rather is conserved. This is known as energy conservation principle.
Energy can be used to do work; in this case, one can say that energy is converted into work. For example, if there is a piston in the container, heating the container will move the piston due to the molecules of the gas producing work on it. Part of the internal energy will be converted into work. In general, part of the amount of heat supplied to a closed system changes its internal energy, and another part is converted to work done by the system on its surroundings. This is the first law of thermodynamics, which is closely linked to the energy conservation principle: if no heat is supplied, the internal energy in a closed system is conserved.

However, most of the systems, including the brain, are not insulated; they dissipate heat in the environment. In this case, if we supply energy, part of it does work, part heats up the system, and part is just dissipated to the surroundings as heat.
It turns out that the more disordered the system is, the less its internal energy can be converted into work. Intuitively, this is because disordered motion is less effective to do work compared with ordered motion. To take this into
account, the free energy concept was introduced. Free energy is the internal energy minus the unusable energy related to the disordered motion of parts of the system. “Free” means it is freely available (though in reality we usually pay money for energy). At least, physically it is free to consume, no further work is needed to obtain it.
The entropy (measure of disorder) of a system multiplied by temperature mathematically defines the unusable energy. Thus, the free energy reflects the maximal part of internal energy the system can convert into work.
Enthropy is also a measure of…information. Intuitively, this is because there is zero information in total disorder. When we add some order to the system, we provide some information about our actions. For example, a book on the table means that somebody has put it there. Hence, there is a link between energy and information, which is very tempting to apply to the brain. This will be the topic of some other posts here.

Kuzma Strelnikov