Stanislas Dehaene

There's a lot in this book so hard to summarise but I'll try and extract some of the gems.
"Natural selection, Darwin's remarkably efficient algorithm, can certainly succeed in adapting each organism to its ecological niche, but it does so at an appallingly slow rate. Whole generations must die, due to lack of proper adaptation, before a favorable mutation can increase the species' chance of survival. The ability to learn, on the other hand, acts much faster-it can change behavior within the span of a few minutes, which is the very quintessence of learning: being able to adapt to unpredictable conditions as quickly as possible. This is why learning evolved. Over time, the animals that possessed even a rudimentary capacity to learn had a better chance of surviving than those with fixed behaviors-and they were more likely to pass their genome".

"Babies therefore possess a vast knowledge of the world, but they don't know everything from the start, far from it. It takes a few months for babies to understand how two objects can support each other." At first, they don't know that an object falls when you drop it".

"Moreover, these changes in synaptic strength do not happen at random: they tend to stabilize the activity of neurons, by reinforcing their ability to excite one another if they have already done so in the past. The basic rule is so simple that it was already hypothesized in 1949 by psychologist Donald Hebb (1904-85). It can be summed up in a simple formula: neurons that fire together, wire togetber. We now understand why this phenomenon stabilizes neuronal activity: it strengthens circuits that have worked well in the past. Synaptic changes that follow Hebb's rule enhance the probability that the same type of activity happens again. Synaptic plasticity enables vast neuronal tapestries, each composed of millions of neurons, to follow one another in a precise and reproducible order".

"Of course, the brain does not keep a record of every event of our lives. Only the moments that it considers the most important get imprinted in our synapses. To this aim, synaptic plasticity is modulated by vast networks of neurotransmitters, particularly acetylcholine, dopamine, and serotonin, that signal which episodes are important enough to remember".

"Remarkably, these waves of synaptic overproduction and pruning do not occur everywhere at the same time." The primary visual cortex, like other sensory regions, matures much faster than higher-level cortical areas. The organizing principle seems to be to quickly stabilize the brain's inputs by freezing cortical organization in early sensory areas, while leaving the high-level areas open to change for much longer. Thus, regions higher up in the cortical hierarchy, such as the prefrontal cortex, are the last to stabilize: they continue to change during adolescence and beyond".

"Babies are champions of learning lan-guages: at birth, they distinguish all the phonemes of all possible languages Wherever they are born and whatever their genetic background, all they have to do is immerse themselves in a language bath (which can be monolingual, bilingual, or even trilingual), and in a few months, their hearing becomes attuned to the phonology of the language that surrounds them. As adults, we have lost this remarkable learning ability: as we have seen, Japanese-speaking individuals can spend a lifetime in an English-speaking country withouterer being able to distinguish the sound /R/ from the sound /L/,"

"Research shows that we lose this ability toward the end of the first year of life." As babies, we unconsciously compile statistics about what we hear, and our brain adjusts to the distribution of phonemes used by those around us.........
Around twelve months of age, this process converges and something freezes in our brain: we lose the ability to learn. Except in extraordinary circumstances, we will never again be able to pass ourselves off as native speakers of Japanese, Finnish, or Hindi our phonology is (almost) set in stone."

"The results suggest that grammatical learning abilities decline slowly during childhood and drop sharply around the age of seventeen. Because takes time to learn, researchers recommend starting well before the age of ten".

"Learning is easier in childhood, while the cortex is still malleable. Before a young child goes to school, some visual regions of the brain have already specialized in recognizing objects, faces, and places--but there are still large patches with little or no specialization (symbolized by empty hexagons). Learning to read invades these labile circuits and blocks the growth of other categories of objects. If a child does not learn to read, those regions become involved in recognizing faces and objects, and gradually lose their ability to learn letters".

"Take musical reading: a musician who learned to read sheet music at an early age has practically double the surface area of his visual cortex dedicated to musical symbols, compared with someone who has never learned music" This massive growth occupies space on the surface of the cortex, and it seems to dislodge the visual word form area from its usual place: in musicians, the cortical region that responds to letters, the brain's letter box, is displaced by nearly one centimeter from its normal position in nonmusicians".

"At any age: the brain retains some of its plasticity throughout its life, especially in its highest-level regions such as the prefrontal cortex. However, everything points to the optimal effectiveness of early intervention. Whether the goal is to make an owl wear glasses, teach an adopted child a second language, or help a child adjust to deafness, blindness, or the loss of a whole cerebral hemisphere, the sooner, the better".

"During evolution, four major functions appeared that maximized the speed with which we extracted information from our environment. I call them the four pillars of learning, because each of them plays an essential role in the stability of our mental constructions: if even one of these pillars is missing or weak, the whole structure quakes and quivers. Conversely, whenever we need to learn, and learn fast, we can rely on them to optimize our efforts. These pillars are:
• Attention, which amplifies the information we focus on.
• Active engagement, an algorichm also called "curiosity," which encourages our brain to ceaselessly test new hypotheses.
• Error feedback, which compares our predictions with reality and corrects our models of the world.

Attention, active engagement, error feedback, and consolidation are the secret ingredients of successful learning. And these fundamental components of our brain architecture are deployed both at home and at school. Teachers who manage to mobilize all four functions in their students will undoubted maximize the speed and efficiency with which their classes can learn. Each of us should therefore learn to master them".

"When a pupil pays conscious attention to, say, a foreign-language word that the teacher has just introduced, she allows that word to deeply propagate into her cortical circuits, all the way into the prefrontal cortex. As a result, that word has a much better chance of being remembered. Unconscious or unattended words remain largely confined to the brain's sensory circuits, never getting a chance to reach the deeper lexical and conceptual representations that support comprehension and semantic memory........This is why every student should learn to pay attention- and also why teachers should pay more attention to attention!"

"American psychologist Michael Posner distinguishes at least three major attention systems:
1. Alerting, which indicates when to attend, and adapts our level of vigi-
lance.
2. Orienting, which signals what to attend to, and amplifes any object of
interest.
3. Executive attention, which decides how to process the attended informa-tion, selects the processes that are relevant to a given task, and controls
their execution".

"The presence of a human tutor, who looks at the child before making a specific demonstration, massively modulates learning. Nor only does eye contact attract the child's attention, but it also signals that the tutor intends to teach the child an important point..........
Learning seems to occur only if the learner pays attention, thinks, anticipates, and puts forth hypotheses at the risk of making mistakes. Without attention, effort, and in-depth reflection, the lesson fades away, without leaving much of a trace in the brain.........
"Metacognition" is cognition over cognition: the set of higher-order cognitive systems that monitor our mental processes......Metacognition plays a key role in curiosity. Indeed, to be curious is to want to know, and that implies knowing what you don't already know. And once again, recent experiments confirm that from the age of one and perhaps even earlier, children understand that there are things they do not know."

"Repeated punishment leads to learned helplessness, a kind of physical and mental paralvsis associated with stress and anxiety, which has been shown to inhibit learning in animals.?
The solution? Most teachers already know it. It is simply a matter of rewarding curiosity instead of punishing it: encouraging questions (however imperfect they may be), asking children to give presentations on subjects they love, rewarding them for taking initiative... The neuroscience of motivation is extremely clear: the desire to do action Y must be associated with an expected reward, be it material (food, comfort, social support) or cognitive (acquisition of information)".

"The Rescorla-Wagner rule assumes that the brain uses sensory inputs (the sensations generated by the bell) to predict the probability of a subsequent stimulus (food). It works like this:
• The brain generates a prediction by computing a weighted sum of its sensory inputs.
• It then calculates the difference between this prediction and the actual stimulus it receives: this is the prediction error, a fundamental concept of the theory, which measures the degree of surprise associated with each stimulus.
• The brain then uses this surprise signal to correct its internal representa-tion: the internal model changes in direct proportion to both the strength of the stimulus and the value of the prediction error. The rule is such that it guarantees that the next prediction will be closer to reality."

"All too often, schools use grades as punishments. We cannot ignore the tremendous negative effects that bad grades have on the emotional systems of the brain: discouragement, stigmatization, feelings of helplessness........"Having a deeply entrenched view that anyone can progress is, in itself, a source of progress. Conversely, children who adhere to the idea that skills are immutable, and that one is either gifted or not, perform worse".

"Regularly testing students' knowledge, a method referred to as "retrieval practice," is one of the most effective educational strategies. 20 Regular testing maximizes long-term learning".

"The best way to ensure retention in the long term is with a series of study periods, interspersed with tests and spaced at increasingly large intervals......What is the most effective time interval between two repetitions of the same lesson? A strong improvement is observed when the interval reaches twenty-four hours probably because of sleep......The rule of thumb is to review the information at intervals of approximately 20 percent of the desired memory duration- for instance, rehearse after two months if you want a memory to last about ten months."

"While we sleep, our brain remains active, it runs a specific algorithm that replays the important events it recorded during the previous day and gradually transfers them into a more efficient compartment of our memory.......Sleep and learning are strongly linked. Numerous experiments show that spontaneous variations in the depth of sleep correlate with variations in performance on the next day. When we learn to use a joystick, for example, during the following night, the frequency and intensity of slow sleep waves increase in the parietal regions of the brain involved in such sensorimotor learning-......Nocturnal consolidation is therefore not limited to the strengthening of existing knowledge. The discoveries from the day are not only stored, but also recoded in a more abstract and general form."
He summarises the key messages of the book as follows:
"* No, babies are not blank slates: as early as the first year of life, they possess vast knowledge of objects, numbers, probabilities, space, and people.
* No, the child's brain is not a sponge that obediently absorbs the structure of its environment. Remember Felipe, the blind and tetraplegic Brazilian storyteller, or Nicholas Saunderson, the blind mathematician who held Newton's chair: such cases show us that sensory inputs can be disruptedo. absent without ruining a child's grasp of abstract ideas.
• No, the brain is not just a network of malleable neurons that waits to be shaped by its inputs: all the large fiber bundles are present at birth, and brain plasticity, however indispensable, typically refines only the last mil.
limeters of our connections.
• No, learning does not occur passively through simple exposure to data or lectures: on the contrary, cognitive psychology and brain imaging show us that children are budding scientists, constantly generating new hypothe-ses, and that the brain is an ever-alert organ that learns by testing the models it projects onto the outside world.
• No, errors are not the mark of bad students: making mistakes is an integral part of learning, because our brain can adjust its models only when it discovers a discrepancy between what it envisioned and reality.
• No, sleep is not just a period of rest: it is an integral part of our learning algorithm, a privileged period during which our brain plays its models in a loop and enhances the experience of the day by a factor of ten to one hundred.
•And no, today's learning machines are nowhere close to surpassing the human brain: our brains remain. for the moment at least, the fastest, most effective, and most energy eficient of all information processing devices, A true probabilistic machine, it successfully extracts the maximum amount of information from each moment of the day and transforms it at nightinto abstract and general knowledge".

As I said at the start, there is a lot in this book. And he seems very certain of his ground and conclusions. (I'm always a bit concerned when people are so convinced of their facts and conclusions...but he seems to be able to justify his conclusions). And it's a fascinating set of conclusions about the way we learn. I will try and put some of this into practice. However, what i'd really like to see is a bit more of how elderly people learn new stuff...not just infants.and school kids. Try learning Japanese at 78 !
Anyway, a very impressive book ....easily worth 5 stars.… (más)

Maybe 3.5 stars. Interesting stuff about how the learning process works within the brain, with some contrast/compare of computer learning algorithms. Some suggestions about how schools should restructure educational techniques in light of knowledge about how learning works.

I felt disappointed that there was very little discussion about how what is learned is actually encoded in the brain for future retrieval. The simple fact is that scientists just don’t know how this works, but I would have loved to hear some intelligent informed speculation. Not sure if this is the cautious scientist sticking to scientific facts, or if the mysteries of how knowledge is stored is still so unfathomable that it’s just not worth speculating about. But I guess I expect that a book about how the mind learns would addressthis situation, if at least to say that nobody has any real idea how information is encoded in the brain.… (más)