Stop sleeping, you'll feel better?!

Imagine yourself in a depressive state. Most of us can do it because most of us have had that experience at least once. What can you do to feel better?

Researchers at the University of Pennsylvania School of Medicine suggest that not sleeping could help. I know, this is completely counter-intuitive. However, there is some logic behind it.

Here is my two cents on how this could actually work.

The main actor of this story is serotonin. Serotonin is a small molecule inhabiting your brain and making you feel happy. But this isn't the only thing serotonin does. Serotonin permits you to sleep. Indeed, in the late evening, with or without a full moon, some serotonin transform itself into melatonin, which makes you feel sleepy. Once asleep, other serotonin transform itself in other ways to keep you asleep. As a result, when you are asleep, your serotonin level is lower, while when you are awake, it is higher.

Now what will happen if you decide not to seep anymore? The serotonin inhabiting your brain will not be used up to put you to sleep and to keep you asleep. As a result, the amount of serotonin in your brain will not decrease at night. Also, during your next meal, you will eat proteins, and a small guy in these proteins, a certain L-tryptophan, will enter your brain and transform into ... serotonin! Thereby, more and more serotonin can build up in your brain, until a normal amount is reached and you do not feel depressed anymore.

You will not feel depressed anymore...but you will be sleep deprived. Seriously, I would not recommend that therapy to my worst enemy. Are they other ways to increase your serotonin level? Yes, there is an easy one. Take L-tryptophan supplements on an empty stomach. You can buy it in your pharmacy or your bio-shop.

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.

Cours-j1-j2-j3-j4-j5-j6-j7-j8-j9-j10-j11-j12-j13-j14-j15-j16-j17-j18-j19-j20-j21-j22-j23-j24-j25-j26-j27-j28-révision-examen

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.

Cours-j1-j2-j3-révision-j5-j6-j7-j8-j9-j10-j11-j12-j13-j14-j15-j16-j17-j18-j19-j20-j21-j22-j23-j24-j25-j26-j27-j28-révision-examen

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

Cours-j1-j2-j3-révision-j5-j6-j7-révision-j9-j10-j11-j12-j13-j14-j15-j16-j17-j18-j19-j20-j21-j22-j23-j24-j25-j26-j27-j28-révision-examen

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

Cours-j1-j2-j3-révision-j5-j6-j7-révision-j9-j10-révision-j12-j13-j14-j15-j16-j17-j18-j19-j20-j21-j22-j23-j24-j25-j26-j27-j28-révision-examen

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.

Book Review: Sight Unseen (M.goodale, A. Milner) Part II:Doing without seeing

Now you will be surprised! You remember that Dee was unable to see the shape of things? Well, as it turns out, if you show her a pencil, she is unable to say what it is, let alone if it is held vertically or horizontally. However, ask her to grasp it and she will grasp it just like anybody else! With the same "on the fly" right orienting of her hand and with the same "on the fly" narrowing of her thumb - index distance! Just like if she could see it!


Just as surprising: She can walk around in a landscape full of obstacles without ever stumbling on any! She avoids them all like you and me!


The authors presented her a mailbox which opening was rotatable so as to enable orienting it in any chosen direction. When Dee was asked to hold an envelope and to rotate the envelope in such a way as to match with the opening of the mailbox: She failed lamentably. She seemed to orient her envelop randomly. But when asked to post the envelop through the slit: she succeeded easily, orienting correctly her hand just like you and me!


The authors asked her to grasp various objects while captors where posed at various parts of her hand so as to be able to analyze finely her moves. She grasps things in the exact same way as anybody else: adapting the orientation of her hand on the fly and adjusting the thumb-index distance to  the size of the object! Objects that she cannot "see" and which dimensions she is unable to guess!


As it turns out, Dee has the part of her vision controlling her actions intact but has the part of her vision constructing her perceptual representations damaged. She is living evidence that part of our vision driven actions are unconscious. We do not need to be aware of the orientation of a slit to be able to slide something in it. However, we do need to be aware of the orientation of said slit to be able to describe it!


We have many independent visually controlled processes in our brain. Many of them (grasping things, walking around avoid things, ...) still work even when, like Dee, we have lost the ability to consciously see these things!


In my next post, you will see how some people have the exact opposite problem than Dee.

Book Review: Sight Unseen (M.A. Goodale, A. D. Milner) Part I : A tragic accident

The undertitle of this book is "An exploration of concious and unconscious vision". This book relates some truly amazing facts about consciousness and vision.

The first chapter relates to a patient of the authors: Dee Fletcher. This woman had an accident. She got poisoned by carbon monoxide while taking a shower. As a result, she suffered some brain damage and lost part of her vision. Dee can still see colours but she cannot recognize her mother. She can see the texture of things but not their overal shape. She can see the hairs on a hand's skin but she cannot recognize a hand. She has vision...without shape. she can tell that something is made of red plastic or shiny metal but she has no idea of the shape of the object. Dee has difficulty to separate an object from its background;

The authors tested Dee scientifically, asking her to perform various controled tasks.

When presented with a line pattern, she could say that they were lines but could not say if they were horizontal or vertical.

When presented with a drawing of an apple, she could not recopy it; but when asked to draw an apple from memory, she did very well.

The rest of her mental live seems to be perfectly normal.

All this seems weird but the result of further tests is even much weirder! (To be continued)

Nuclear Fission Chain Reaction.mov

Do you find this video relaxing?

Put the audio level low. This is an experimental video making use of our "orienting response reflex" by presenting to us new information every 2.5 seconds. During the "orienting response" which is a mental state in which most animal find themeselves when presented with something new, our heart rate is decreased and our brain blood vessels dialtes in order to increase our brain readiness to acquire information in order to react vis-à-vis this "something new". This vidéo is from ansgar1965 and is experimental (not tested, you are the cobayes. So what do you think? is it relaxing?)

Book Review: Consciousness Explained (D. Dennett): Part VI:The Precognitive Carousel

Dennett reports an experiment made by Grey Walter. It consisted in presenting a carousel projector for showing slides to patients having electrodes implanted in the motor cortex of their brain. The patients were given a controller with a button for them to push on when they wanted to switch from one slide to the next. Actually, the controller was a dummy controler and the slides where changed in function of the signal received by the electrodes. The results? The patients experienced that the slide projector was anticipating their decisions. The slides would change just before they had decided to change them. This again seems to point to consciousness arising after that the decision is made. Dennett however once again express his view that timing of conscious events is not possible. an opinion of him that I still need to study further before to accept it or to reject it.

I received an interesting message on Facebook from a reader (Jason Weber). I will probably post it as a note to chapter V.

Book Review: Consciousness Explained (D. Dennett): part V : Delay of consciousness

In the 80's, Libet reported an experiment where subjects (wearing scalp electrodes) were asked to flex one hand at the wrist while noting the position of a moving spot at the precise time they formed the intention to flex. Afterwards, said subjects reported where the spot was at the moment they decided to flex their hand. The electrical measurements performed by the electrodes permited to determine that the subjects flexed their wrist 350 to 400 ms before the time indicated by the subject as being his time of intention to flex.


This experiment seems to indicate that we are conscious of the decisions made by our brain AFTER they have been made.


It seems to me  that Dennett does not like this conclusion (although he does not express it explicitly) which seems to contradict the intuition that our conscious acts control our bodily motions.

He considers this kind of explanation as being stalinesque (i.e. presuming that the brain delays consciousness in order to be able to presents all the facts it wants to present in the order it wants them to be presented).


He points out that there is an alternative explanation: "the subjects were conscious of their intentions at an earlier moment, but this consciousness was wiped out of memory (or just revised) before they had a chance to recall it". He calls this kind of explanation "Orwellian" because history is re-writen after the facts.

Finally, he also points out that yet another explanation which is that "an element of content becomes conscious at some time t, not by entering some functionally defined and anatomically located system, but by changing state right where it is: by acquiring some property or by having the intensity of one of its properties boosted above some threshold."

Dennett seems to doubt very much the possibility to equal the time of reporting of the subject with the time of conscious experience.


Personally, I would call on Ockham's razor with such an issue: stick to the simplest hypothesis until proven otherwise. Hence, as far as I am concerned, this experiment seems to indicate that consciousness arises after the facts. Clinical cases like the case of Mrs. Dee in "sight unseen" are also pointing toward such an explanation.


I think Dennett doubly dislikes the results of this experiment. 1) as mentioned earlier, it places consciousness after the events and 2) it looks like we are watching a movie of our live in a cartesian theater (he despises the idea of the cartesian theater).


[this page has been amended on 12/03 after a reader pointed to me some errors of interpretation. Thanks to Jason]

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.

The Standford Prison Experiment

For those of you who haven't seen this video yet, it is a must see to get an glimpse at the dark side of our human nature.