How to learn most effectively

The advice in this article were largely inspired by a series of lectures given by Professor Stanislas Dehaene at the College de France on memory and its optimization.


 1) Focus on your subject of study.

For example, playing during your sleep a recording of what you wish to study has no effect if you never studied that subject matter before. It is important to be awake and to place yourself in conditions where distractions are minimal. For example, studying with television in the background is not very effective.

 2) Strive to understand or make sense of the materials.

For example, if you are asked to learn the phrase

"The boy threw his popcorn because the cage broke."

Your ability to remember this sentence will be much better if you are given the following hint:

"Lion"

In fact, now you understand why the cage is broken and why popcorn has been spilled. It will now be much easier to remember that phrase.

Your memory of this sentence will, however, be even better if you had not been given the indication right away and if you were first left guessing why the cage was broken and why the popcorn was spilled.

 3) Incorporate testing periods in your study program.

The brain learns best when it realizes that it is in error and when it receives the correct answer as feedback to its error. We must therefore test ourselves on a regular basis in order to generates these mistakes as often as possible during study and after each mistake, we must check what the right answer was. Take the example of a vocabulary list that takes 30 minutes to be read carefully. It is better to spend an hour on these words by studying the list once but trying to guess the translation of each word before looking at the translation than to read the list of words twice attentively but without testing.

 4) Sleeping breaks are essential.

a. Before an examination
Memory is consolidated during sleep. The night before an exam, you get better results by studying once a material for 6 hours and then sleeping six hours than by studying the matter twice (in 12 hours) without sleep before going to the exam. Also, if you study the morning for a test taking place in the afternoon, it is recommended to take a nap between the study session and the test.

b. Between two study sessions of the same material
It is more efficient to separate your study sessions of the same material by at least one night. For example, it is better to study two different materials or two chapters on the same day (one in the morning, one in the afternoon) and to repeat that same study pattern the next day than to study a first material or chapter twice on the same day and to study the next material or chapter on the next day. 

c. After a day preferably solely devoted to the study
Sleep consolidates memories while giving priority to the most important events of the day. A study period is a period of concentration, it is an important event in a day. Watch Out! Watching a movie or playing a video game will also be considered an important event, not only because it also focuses your attention but also because it is rich emotionally. This kind of activity is going to compete with your study material during your sleep. So it is better to do nothing too intense or captivating during study days.

d. Using smells
Select a fragrance to perfume the pages of your study material and perfume your room with the same fragrance. While you sleep, the smell will lead your brain to spend more time on the events related to that fragrance (your study material) than on events that are not related to that fragrance (it is counterproductive to wear this perfume on yourself the whole day). Sounds can be used in the same manner. For example, using the same background music for studying and for sleeping. Similarly, a recording of the study material or words reminding the study material can be played at night but beware, there is a risk of disrupting your sleep by causing for instance small awakenings. Also, playing a record of your study material is useless if you never studied it before.

 5) Carefully plan your study sessions

Watch Out! Maximizing memory in the moment of the study session is not necessarily maximizing long-term retention! So you will sometimes develop radically wrong opinions on the best way to study.

It is important to space your study sessions of the same material. As we have seen in point 4b, it is better to space two study sessions of the same material by an interval of at least one night. However, spacing your study sessions is also beneficial within one day of study. For example, it is more effective to space two study sessions of the same material with an hour interval than with a 5 minutes interval.

Let us now see some very concrete cases:

a) If you only want to pass the exam without worrying about retaining the material for the long term and if you have not taken the course:

1. If you have the time to study only once: you must study the day before,

2. If you have the time to study twice, you must study the day before and the day before that day,
...and so on.

This type of study is effective for an exam. However, beware that this strategy is the worse possible if you wish long term retention of what you studied, study sessions being too close together. The time commitment is large for a poor outcome in the long term.

b) If you want to get the most value for your time and / or study for the long term:

The optimal strategy will depend on what you mean by long term.
If you have studied the material for the first time today (e.g. you had your course today), you'll have an exam in x days and you have the time to make a single revision, the revision should be done the day before.

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However, if you have the time to do two revisions, make a first revision in (x / 7) days and the second revision the day before the exam. For example, if you have an exam in 30 days make your first revision in 4 days and a second revision on the day before the exam.

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It will be noted that once the first revision is scheduled and the last revision is scheduled for the day before the exam, the perfect time to do an additional revision will be (30d-4d) / 7, that is to say again 4 days after the first revision

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And the perfect time to add one more revision will be (26j-4d) / 7, that is to say, three days after the previous one.

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Note that as we get closer to the exam, revisions get closer to one another. These will therefore become less and less effective for long-term retention. This type of method is a good compromise between exam success and retention of the material over the long term. Even for the unambitious student, this type of strategy is interesting because it allows quite some retention of the study material if it is re-tested or useful for another exam along the line.

By cons, if you have studied the material for the first time today, and you do not know when you will need to know this material (for example, you study for fun and no examination is expected), make revisions increasingly spaced. For example, the next day, then a week later, then a month later, then three months later, etc. This will maximize the long-term retention.

Comment apprendre le plus efficacement possible ?

Les conseils prodigués dans cet article ont été largement inspiré d’une série de cours donnés par le Professeur Stanislas Dehaene au Collège de France sur la mémoire et son optimalisation.

 1)      Il faut être concentré sur ce que l’on étudie.

Par exemple, faire passer pendant son sommeil un enregistrement de ce que l’on désire étudier n’a aucun effet si cette matière n’a jamais été étudiée auparavant. Il est important de se mettre dans des conditions où les distractions sont minimales. Par exemple, étudier avec la télévision en fond sonore est peu efficace.

 2)      Il faut faire l’effort d’essayer de comprendre ou de donner du sens à ce que l’on étudie.

Par exemple, si l’on vous demande de retenir la phrase

« le garçon renversa son pop-corn parce que la cage se brisa ».

Votre mémoire de cette phrase sera bien meilleure si l’on vous donne l’indication suivante :

« lion »

En effet, maintenant vous avez compris pourquoi la cage s’est brisée et pourquoi le pop-corn s’est renversé. Vous avez maintenant beaucoup plus facile à retenir la phrase.

Votre mémoire de cette phrase sera cependant encore meilleure si l’on ne vous avait pas donné l’indication tout de suite et si l’on vous avait d’abord laissé essayer de deviner pourquoi la cage s’est brisée et pourquoi le pop-corn s’est renversé.

 3)      Il faut incorporer des périodes de tests dans son étude.

Le cerveau apprend au mieux lorsqu’il se rend compte qu’il est dans l’erreur et lorsque la correction de son erreur lui est ensuite présentée. Il faut donc faire des erreurs le plus souvent possible pendant l’étude et après chaque erreur, regarder qu’elle était la bonne réponse. Prenons l’exemple d’une liste de mots de vocabulaire qui met 30 minutes à être lue avec attention. Il vaut mieux passer une heure sur ces mots en étudiant la liste une seule fois mais en essayant de deviner la traduction de chaque mot avant d’en regarder la traduction, que de lire la liste de mots deux fois avec attention mais sans se tester.

 4)       Il faut dormir.

a.       Avant un examen

La mémoire se consolide pendant le sommeil. La veille d’un examen, on obtient de meilleurs résultats en étudiant une seule fois une matière pendant 6 heures, puis en dormant 6 heures qu’en étudiant la matière deux fois (en 12 heures), sans dormir avant de se rendre à l’examen. Aussi, si l’on étudie le matin pour un examen ayant lieu l’après-midi, il est conseillé de faire une sieste entre la session d’étude et l’examen.

b.      Entre les sessions d’études d’une même matière
Il est plus efficace de de séparer ses sessions d’étude d’une même matière par au moins une nuit. Par exemple, il vaut mieux étudier deux matières différentes ou deux chapitres différents sur une même journée (un le matin, un l’après-midi) et recommencer l’étude de ces deux matières ou chapitres le lendemain, que d’étudier la première matière ou le premier chapitre deux fois la première journée et la seconde matière ou le second chapitre deux fois le jour suivant.

c.       Après une journée de préférence uniquement consacrée à l’étude
Le sommeil consolide en priorité le souvenir des évènements les plus marquants de la journée. Une période d’étude étant une période de concentration, c’est un évènement marquant. Attention ! Regarder un film ou jouer à un jeu vidéo sont aussi des évènements marquant non seulement car ils requièrent de l’attention mais aussi car ils sont riches émotionnellement. Ce genre d’activité va donc rentrer en compétition avec l’étude pendant la nuit. Il est donc préférable de ne rien faire de plus marquant que l’étude pendant une journée d’étude.

d.      En utilisant les odeurs
Réservez un parfum pour parfumer vos feuilles de cours et parfumez votre chambre de ce même parfum. Pendant votre sommeil, l’odeur mènera votre cerveau à passer plus de temps sur les évènements liés à ce parfum (votre étude) qu’aux évènements qui n’y sont pas lié (il est donc contreproductif de porter ce parfum sur soi toute la journée). Les sons peuvent être utilisés de la même manière. Par exemple en utilisant la même musique d’ambiance pour l’étude que pour la nuit. De même, un enregistrement du cours ou de mots rappelant le cours peut être joué pendant la nuit mais attention, il y a un risque de perturber le sommeil en provoquant par exemples de petits réveils. Aussi, la méthode auditive ne sert à rien si l’on a jamais étudier cette matière auparavant.

 5)      Il faut programmer judicieusement ses sessions d’étude

Attention ! Ce qui maximise la mémoire dans l’instant de la session d’étude n’est pas nécessairement ce qui maximise la rétention à long-terme !  On se trompe donc parfois radicalement sur les conditions d’étude qui optimise la mémoire.

Il est important d’espacer ses sessions d’étude d’une même matière. Comme nous l’avons vu au point 4b, il vaut mieux espacer deux séances d’étude d’une même matière par un intervalle d’au moins une nuit. Néanmoins, espacer ses sessions d’étude est également bénéfique au sein d’un même jour d’étude. Par exemple, il est plus efficace d’espacer deux séances d’étude d’une même matière d’un intervalle d’une heure que d’un intervalle de 5 minutes.

Voyons maintenant quelques cas de figures bien concret :

a)      Si vous ne voulez que réussir l’examen sans vous souciez d’avoir retenu la matière sur le long terme et que vous n’avez pas suivi le cours:

a.       Si vous n’avez le temps que d’étudier une seule fois : il faut étudier la veille,

b.      Si vous avez le temps d’étudier deux fois : il faut étudier l’avant-veille et la veille,

Et ainsi de suite.

Ce type d’étude est efficace pour passer un examen. Par contre, cette stratégie est la moins efficace possible pour retenir l’information sur le long terme, les sessions d’études étant trop rapprochées. L’investissement en temps est important pour un résultat sur le long terme médiocre.

b)      Si vous voulez rentabiliser votre temps passé en cours et/ou étudier pour le long terme:

La stratégie optimale va dépendre de ce que vous entendez par long terme.

Si vous avez étudié la matière pour la première fois aujourd’hui (ex : vous avez eu votre cours aujourd’hui), que vous aurez besoin de connaitre l’information dans x jours et que vous n’avez le temps que de faire une seule révision, faite la révision la veille.

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Par contre, si vous avez le temps de faire deux révisions, faite une révision dans x/7 jours et la seconde révision la veille de l’examen. Par exemple, si  vous aurez un examen dans 30 jours, faite votre première révision dans 4 jours et votre seconde révision la veille de l’examen.

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On remarquera qu’une fois la première révision faite et la dernière révision programmée pour la veille de l’examen, le moment idéal de faire une révision additionnelle sera (30j-4j)/7, c'est-à-dire encore une fois 4 jours après la première révision

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Et le moment idéal pour ajouter encore une révision sera (26j-4j)/7, c'est-à-dire 3 jours après la précédente.

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On remarque qu’au fur et à mesure que l’on se rapproche de la date d’examen, les révisions se rapprochent. Ces révisions deviennent donc de moins en moins intéressantes pour la rétention à long terme. Ce type de méthode est le bon compromis entre réussite aux examens et rétention de la matière sur le long terme. Même pour l’étudiant peu ambitieux, ce type de stratégie est intéressante car elle permet de ne pas avoir trop oublié la matière si elle est re-testée ou utile pour passer un examen ultérieur.  

Par contre, si vous avez étudié la matière pour la première fois aujourd’hui et que vous ne savez pas quand vous aurez besoin de cette matière (par exemple, vous étudier pour le plaisir et aucun examen n’est prévu), faite des révisions de plus en plus espacées. Par exemple, le lendemain, ensuite dans une semaine, ensuite dans un mois, ensuite dans trois mois, etc. Cela maximisera la rétention à long terme.

Book Review: Sight Unseen (part III). Are frogs conscious?

As I indicated in part II, although she has no conscious experience of the presence of a pencil, Dee Fletcher is able to catch a pencil using the same hand orientation as would a person with unimpaired vision.

As it turns out, some people have brain damages that cause the opposite effect: They can see and describe a pencil (they are consciously aware of the presence of a pencil) but they are unable to make the necessary movements to grasp it (Balint's syndrome). What these people have is not a motor problem. Balint "...could deduce that from asking the patient to point to different parts of his own body using his right hand with his eyes closed: there was no problem."

From the analysis of Dee Fletcher's case, it seems that when we are reaching for a pencil, we think that we need to be aware of the presence of the pencil, but actually not. We do not need to be aware of its presence. Dee Fletcher is not aware of its presence, but she can catch it. Reaching for objects is an ability that has been hard wired in our brain far back in our evolutionary history and it did not require consciousness. For this kind of motor acts at least, we are not better than "zombies".

A further indication that it is indeed so comes from experiments on animals:

When frogs catch preys, they use a different brain module from the one that guides them around visual obstacles blocking their path. This has been demonstrated in the following experiment:

First of all, they are two things that you need to know about frogs:

1) frogs’ brains can regenerate new connections when damaged.

2) the right eye of a frog is connected to the left hemisphere of its brain (and vice versa).

In these experiments, the optic nerves that brought information from the right eye to the "prey catching part" of the brain were cut. A few weeks later, however, the cut nerves re-grew and connected with the "prey catching part" of the brain but on the wrong side of the brain. As a result, when these frogs were brought in presence of a pray on their right side, they tried to catch it on their left side. However, when brought in presence of an obstacle on their right side, the frog correctly avoided the obstacle (this because the "obstacle avoiding part" of their brain had not been rewired.

The "prey catching part" in these frogs was now wired up the wrong way around.

But this did not mean that their entire visual world was reversed. It was as though the frogs saw the world correctly when skirting around an obstacle, but saw the world mirror-imaged when snapping at prey. Hence, frogs do not experience a global visual world created for all purposes. Frogs have specialized parts of their brain using visual information independently to perform different tasks.

Does that mean that frogs do not experience a visual world at all? Maybe they do, but as a matter of fact, they do not need one for catching prey or avoiding obstacles. By the way, we also do not need one for catching objects or avoiding obstacles. But we do experience a global visual world. This conscious visual experience might only be present in animals needing to communicate and/or to plan ahead...

For a long time I thought that any animal with a memory was conscious. Maybe frogs are conscious to some extend but it seems that they can function without experiencing a visual world as we do. Their kind of consciousness, if it exists, might be very different from ours.

Consciousness Explained (D. Dennett): Part VIII; The Baldwin effect

We are the result of natural selection. Natural selction works by 1) allowing mistakes in the genome of an animal's offspring and 2) selecting the offsprings whose genome makes them better at survival/reproducing. If you are not familiar with this concept, go to buy "the selfish gene" from R. Dawkins (a live changing book).

The Baldwin effect is a mechanism that speeds up natural selection in a very peculiar way. It require you to have a plastic nervous system, in short: an ability to learn. If there is a "good trick" out there for an animal to learn, e.g. a behaviour that would greatly enhance an animal success at reproducing, any animal having this good trick hard-wired in its genome would be at an advantage. However, since having this "good trick" within it would be an all or nothing story, there maybe lacking a sufficiently progressive slope for natural selection to opearte swiftly. Hence, the time for this trick to be hard-wired in every animal within its species might be very long indeed. See left side of the figure below:

However, species not having this good trick hard-wired in their genome but having a plastic brain wired in such a way that they are capable to learn that trick during their livetime, are able to evolve the hard-wirering of this trick much faster. Here is how it works: Animal A has a brain slightly more able to learn the good trick than animal B. Animal A has therefore an advantage over animal B and will therefore probably leave more offsprings. Amongst said offsprings, animal A', due to a fortunate mutation, is still beter at learning the trick than its parent was, A' acquires it faster in his livetime than his siblings and therefore outcompete them and makes more offsprings. Amongst the kids of animal A', animal A'' is gifted with a further fortunate mutation that makes him particularly able to learn the good trick...and so on and so forth until the good trick (or at least the ability to learn the trick damned-easy) is practically hard-wired in the genome. What the Baldwin effect provides is a gentle slope for natural selection to operate on (see right side of the figure above). Any small improvement in the learning ability of the individual gives him a higher chance to hit on the good trick(s).

This makes clear the big advantage that a plastic brain provides to a species.

Book Review: Consciousness explained.Part VII. The evolution of consciousness

Daniel Dennett proposes the following evolutionary scenario for consciousness:

1) In the environment on earth before the appearence of life, some molecules acquired the ability to replicate (Richard Dawkins would call them replicators). This creates a point of view from which the world's events can be roughly partitioned between the favorable to this replication, unfavorable to it or the neutral".

2) "As soon as something gets  into the business of self-preservation, boundaries become important, for if you are setting out to preseerve yourself, you don't want to squander effort trying to preserve the whole world: you draw the line."

3)Next in line comes a certain ability to react to direct stimuli upon contact. E.g. engulfing food you touch or coiling away from harmful things you touch. This is the most rudimentary type of nervous response. It is a very crude way to predict the future. If I don't recoil, I will get eaten/destroyed/damaged.

4)Next, comes short range anticipations like the ducking reflex that permits to avoid being hurt be a projectile. Such reflexes are hard wired, including in humans (newborn infants have it). An interesting fact Dennett points out is the ability of many animals (from fish to humans) to be particularly sensible to the presence of a vertical axis of symmetry in its visual field. This is presumably caused by the fact that in our evolutionary past the most likely item in our environment having such an axis would have been a predator, a prey or a mate facing you. He argues that the fact that such alarm mechanisms are so crude, has the advantage of being fast and economical at the cost of many false alarms (the vision of a quasi symetrical tree for instance). For such a trick to be selected by evolution, it only has to give to its owner a slightly higher than otherwise chance to survive or to mate.

5) Once such a signal is detected, a further evolutionary advantage is achieved by a discrimination process capable to determine (at least in a crude way) if the first crude signal was a predator, a prey or a mate. In some fish, the vertical symmetry signal triggers an "orienting response", i.e. a swift interuption of ongoing activity. Dennett says that we have many such subsystems running unconsciously and performing specialized tasks.
When an alarm signal is recieved, e.g. due to the perceiving of symetry, our system stops and all our senses are open to maximize the input of information. If the alarm is confirmed, we get a rush of adrenaline and we react by e.g. fleeing. He says monst animals have such a system and he sees such "orienting responses" as a precursor to what we call our state of conscious awareness.

6) The animal acquired the ability to trigger such an "orienting reponse" also as a consequence of internal stimulis (not only external inputs such as symetric objects).

7) "Regular vigilance" turned into "regular exploration" where the animal frequently acquire information for its own sake, just in case it turns out useful in the future. E.g. primates with their saccaded eye movements scan uninteruptly their environment.

That's already a nice start I think...

My own opinion on "consciousness"

Consciousness and memory

I will try to explain what is my vision of what I think consciousness might encompass. I am sure I do not understand fully what consciousness is (otherwise I would not be reading and thinking so much about it). I however partly developed and partly stole ideas that, put together, gives me a hypothesis of what consciousness could be.

It all started I think in 2007 when I was driving back from a patent law course in Antwerp. It was dark, there was nothing on the radio and I thought "you have no opinion whatsoever on what consciousness could be. Why don't you try to make yourself one by developing it from first principles?"

And so I started to think about what was necessary for experiencing consciously something? I started to reason: "if I hear something (e.g. a word) I can be conscious of it. Why?" How do I know that I heard it? Answer:"because it is in my memory and I can retrieve it. If it was not there, I would not know I heard it".

Then I thought "OK! So what happens exactly when I hear a word, e.g. the word 'abracadabra'?"
I thought that I first hear each sound of the word and that my brain "recognises" it. So I first hear the beginning of a "a", then the end of a "a" then the beginning of a "b" and so on.

But what would happen if I did not have a good memory? I might forget the beginning of the word at the time I am hearing the end of the word and this word would not make sense to me but I would nevertheless be conscious. However if you ask me 10 seconds after having telling me the word "abracadabra" whether I heard it (actually I would not even understand your question and I would not be able to answer it... but let say for the sake of this thought experiment that my memorisation capacity was brought back to normal before you asked me this question), I would answer "no" since I would have forgotten this word already.

Now let's decrease my memory even further to a time span of let say one millisecond. I would hear the beginning of a "a", then forget it, than I would here the middle of the "a", then forget it, then I would hear the end of a "a", then forget it. I would have some kind of rolling consciousness with a very short time span. This would be so far from what we experience as human conscious beings that we can hardly still call that a conscious state.

What would we experience if our short time memory had a time span infinitesimally short? Or no memory at all? I claim that this would equal to not being conscious.

From this thought experiment, I concluded that without memory, no consciousness.

Puropose or cause of consciousness

I then proceeded to think "aha! Memory is necessary for consciousness. Could it be that consciousness evolved together or after memory? Could it be that consciousness serves a purpose linked to memory or that being conscious is what it feels like to memorise?".

I then realised that we can be more or less conscious. We can be very aware of something or almost not aware at all of this thing. For instance, I was driving since half an hour but I was only barely conscious of the road. At other times I am very conscious of the road. So what could be the purpose of something varying in intensity and potentially serving memory?

I thought BINGO! Consciousness with its varying levels of intensity could serve as labels! Consciousness of something with a particular level of intensity could be a "label" informing the memorisation processes of the brain on the importance of said thing. It could also be the other way around. Maybe we just experience stronger consciousness feeling for stronger memories.

For instance, you see a free lion in front of you: you will be VERY conscious of its presence and your brain will record very deeply (and forever) this information instantaneously in your long term memory.

Another example: you see a small stone on the road. Your eyes saw it. This information entered your short term memory but you will not be very conscious of it at all. As a result, your memorisation processes having received the "low consciousness" label associated with this stone, you will quickly forget it and you will never ever be able to recall it.


Actually, we are at any given time bombarded with thousands of inputs, both internal and external. Our senses are incessantly receiving information. If we had to memorise all of them vividly and for ever, our memory would be full in no time. We therefore need to rank information by order of importance, in other words: we need a filter. This filter might or might not be consciousness.

This information is important for our survival (e.g. uncaged lion) or our reproduction (e.g. sexy lady/man)? Our brain attaches the label "very conscious" to it and it gets written deep into our memory.

Is this information unimportant (e.g. one tic of a clock amongst many)? Our brain attaches the label "barely conscious" to it and this information will quickly be forgotten.

Actually, we could very easily replace the word "consciousness" by the word "attention" in the last part of my analysis above.


Also, I could make sense of the same insights by making the alternative hypothesis that a label (or filter) (which is not "consciousness" but well "attention") is attached to each input and what we "feel", i.e. what we are "conscious" of is the process of memorisation. When something is memorised, we are conscious of it. When it is deeply memorised, we feel deeply conscious of it.


Another facet of what I think consciousness is comes from experiments in experimental psychology which all tend to indicate that our brain already knows we will move our wrist before that we are ourselves aware that we will move our wrist (Libet et al, 1983). I think this kind of experimental results fit nicely with my vision above because when your arm moves, it is best for you to keep in memory that it did! As a result, this information is engraved in your memory and you are simultaneously conscious of it.

You are conscious of many things your body experience but you are feeling it "after the facts".


This vision of consciousness is also compatible with my vision of free will (there is no free will).


We are spectators of our own lives. Just like when we go to the movie: sometimes we really think we are living it. Well, we also really think that we are in charge of ourselves...but we are not. The illusion is however almost perfect. This illusion falls apart e.g. when lesion to the primary visual cortex occurs.


Imagine that in the future we would be able to watch a movie while simultaneously feeling and thinking absolutely all what the actor feels and think. We would very easily be convinced that WE are the actor and that the actor that WE are has free will.


Later I would like to make a post on these psychological experiments I referred to. I also would like to speak about split brains, phantom limbs, rubber hands, and Mrs. Dee (a woman whose brain has been damaged and whose case is detailed in the book "sight unseen").

Book Review: Consciousness Explained (Daniel C. Dennett): part IV (his model of consciousness)

The main purpose of Dennett's book is to 1) refute the carthesian theater model of consciousness (see image below), and 2) introduce his own new model instead. He calls his new model the multiple drafts model.


The Cartesian Theater:


A representation of the carthesian theater model of consciousness is depicted below:



In this picture, we can see the head of a man looking at an egg being fried in a frying pan. Inside this man's brain, a screen is present where the vision of the man is projected for a smaller man to look at. The smaller man (or homonculus) is a methaphor for a central part in the brain where "consciousness happen".
The carthesian theater model assumes that their is a central "organ" in the brain where what happens is what you are conscious of. Its most naive form is the idea that a spectator must be present in the brain in order for the senses inputs to be experienced. Descarte for instance considered the pineal gland to be such a center from where the input of the senses could be transduced from mechanical signals (Descarte was not aware of the electrical nature of these signals) to spiritual meanings for the soul's benefit.


The Multiple Draft Model:




In this model, there is no centre where everything has to converge in order to be experienced. On the contrary, different conscious events are generated at different places in the brain. Each element within an event is discriminated only once. For instance, if you see a cow, the brain discriminate the presence of a large object, then it notice it is an animal, then that it is a cow. The discrimination and its fixation in the memory is enough for the phenomenum to be conscious (if probed).
What will be conscious will depend of the time of the probing. If you probe too early, you will only experience the diffuse presence of a large object. If you probe very late, you will have forgotten everything.
There is no need for the discriminated element to be sent or linked to a central theater. The conscious experience will originate from the locus of the discrimination. Also, each element is constantly updated/modified (e.g. interpreted, refined, partly erased, ...) due to interaction with the rest of the brain (pre-existing memories, new inputs, ...).
The multiple draft model makes"writing it down" in memory criterial for consciousness.


This can be best understood by looking at the color phi phenomenom at the bottom of this post (I do not insert it here because it is a moving image that would disturb your reading). To most people, the color phi phenomenom is experienced as a red spot traveling from left to right and changing color midway to become green. However (and you can easily convince yourself thereof by hiding one of both spots), it is in fact nothing of the sort. It is simply two fixed spots, one red and one green, the first blinking out of phase with respect to the second.


When experiencing the color phi phenomenom, the brain does not need to place intermediate spots after having experienced the second spot because there is no part of the brain present to "watch" these intermediate spots, your brain (i.e. you) just "knows" that the spot moved.


When remembering past events, you don't feel them happening again, you just know they happended. For instance, if you try to remember with as much details as possible the pain you experienced the last time you knocked your toes against an obstacle, you will not experience real pain, you will just realize that you "know" what kind of pain it was (which intensity, which location...).


His model makes a lot of sense but what remains unclear to me is the following:


At any given time our brain is processing a lot of inputs: external inputs from our various senses and internal inputs. We clearly do not feel conscious of them all. Cerrtainly, we do not feel conscious of many of them "simultaneously". Dennett seems however to say that whenever an object of our phenomenology is discriminated by our brain, it is "conscious".


On another hand he alludes to the notion of probing. Probing that would determine what is reported as conscious. He seems to make a difference between what is conscious and what we report as conscious experience when asked (i.e. probed) to report.


What I don't get is what he exactly means by his notion of "probing". I get it only partialy. I get it when by probing he means triggering a report from the conscious subject: e.g. asking the guy what he sees/feel. However, we are not constantly being asked to report on our internal states and we feel nevertheless conscious in these apparently "non-probed" times.


Of course, I suspect that his notion of what the probing is is more subtle than that. I suppose that internal inputs and external inputs can themeselves serve as "probes".


Maybe this notion is better explained in the rest of the book.


Once very important phrase he wrote is "The multiple draft model makes"writing it down" in memory criterial for consciousness".


I fully agree with the fact that writing something down in memory is critical for consciousness!


I have my own partial theory on consciousness and I should maybe explain it here before to continue Dennett's book. In view of the bold sentence above, I suspect that his views and mine overlap largly.