the evolution of the reading brain lit psych

The Importance of Plasticity

• Humans have evolved to speak, but not to read

• Speaking and listening are primary language skills

  • Does not require explicit instruction to learn

  • Already has brain pathways evolved to handle it

• Reading and writing are secondary language skills

  • Requires explicit instruction to learn

  • Does not have brain pathways evolved to handle it

  • Each child’s brain must evolve its own pathways for reading

• ​​The brain is more flexible in children

• Plasticity decreases with age

  • As the processes of synaptogenesis and pruning are completed

• Plasticity at the age of reading instruction is important to learning

Developmental Processes

• Biologically Primary Abilities utilize experience-expectant development

  • General, species-typical development that requires the same basic, common human experiences to develop normally. The brain expects this development and is set up to develop it through regular development.

• Biologically Secondary Abilities utilize experience-dependent specialization

  • the brain develops specific, efficient neural pathways and functions in response to an individual's unique experiences throughout life. It involves the creation and reorganization of synaptic connections that are not pre-programmed but are sculpted by specific environmental input

Neuronal Recycling (Dehaene)

• Each person’s brain has to create its own reading circuit by recycling parts of the brain previously used for other purposes

• The brain repurposes existing neurological networks that are cognitively or perceptually related to the new needs

• Reading areas in humans use recycled/repurposed areas used for visual perception in other primates

• ​​“Neuronal recycling” is constrained by biology

• Like the recycling of trash materials is constrained

  • Recycled glass or paper cannot be turned into ANY object

  • The materials have intrinsic physical properties that make them more suitable for certain uses than for others

Visual Adaptation

• The brain divides visual work into categories, each of which is processed by a different part of the cortex

• Distinct zones or “microterritories” have groups of neurons that are specialized to detect different categories: faces, tools, animals, vegetables, digits or letters

• Brain lesions suggest that damage to a particular area can very specifically impact knowledge of a particular category

Adaptation of the Visual Word Form Area (VWFA)

• As we learn to read, this area adapts and transforms 

• This brain region was originally used to recognize faces and objects, and continues to serve this function in non-readers 

  • In readers, face recognition gets moved to the right side of the brain

Ventral Pathway

• Neurons along the ventral pathway make higher-level determinations about what is being viewed 

• Particular areas along this route become specialized for particular objects to identify

Primate Visual System

• Fine-grained neuronal code for visual objects in monkeys

• Neurons in the monkey’s brain can be remarkably selective to the sight of particular objects, faces, or scenes

• Among the 100 images that were presented to this neuron, only the sight of a chair strongly enhanced its firing

• Neurons are specialized to the point of recognizing a single object or person

  • “The Grandma Cell”

Neuron in the visual cortex

Neurons in the visual cortex are feature detectors–they respond selectively to specific features (e.g., lines, edges, angles)

Lateralization

• Millisecond-by-millisecond time course of brain activity during recognition of faces vs. letters

• Initially, the face and letters evoke similar visual activation

• By about 150 milliseconds

  • Letters routed to “letterbox” in left hemisphere

  • Faces routed to a symmetrical region in the right hemisphere

What happens when we view faces?

• (This is an underside view of the brain, so the hemispheres look reversed)

• Bilateral activation to faces

• Greater activation in right hemisphere

• Makes sense, given the VWFA has taken some space in the left hemisphere

History of Alphabetic Systems

• Reading is evolutionarily new, dating back less than 6,000 years 

• Difficulty of determining the “first alphabet” 

• Various systems were created 

  • Clay tokens from Tello

  • Incan Quipas from South America 

• Then cultures began to use writing systems 

  • Hieroglyphs from Egypt 

  • Cuneiform writing from the Sumerians 

Features of Alphabetic Systems 

• Symbolic representation 

  • Symbols convey meaning 

• Logogrpahic 

  • Symbols represent a whole word (or morpheme = word part)

• Pictorgraphic 

  • Pictorial symbols are use to represent objects, ideas, or concepts 

• Rebus principle 

  • Symbols represent language sounds in a general way 

    • The word for life “til” was represented by an arrow (pronounced “ti”)

• Alphabetic principle 

  • Each sound in the speech stream could be separated and represented by a letter

Limits of Pictorgraphic Systems

• Elaborate pictures take time to reproduce 

  • Demotic script (script of the people) was introduced in Egypt, which included more simplified symbols than traditional hieroglyphics 

• Pictographic systems aren’t immediately understandable without training 

  • Especially when pictures are intended to convey more abstract ideas 

  • They could be interpreted differently by different individuals and cultures

Importance of the Greek Alphabet (750 BC)

• The great accomplishment of the Greek alphabet was the awareness of speech sounds 

• First to use the alphabetic principle 

  • Each sound in the speech stream could be separated and represented by a letter 

  • Allowed ease of understanding and new access to the masses 

  • Could be used to express ideas without confine 

• Led to changes in writing and thought 

Cognitive benefits of the new alphabet

• Cultural memory 

  • People no longer had to carry the cognitive load of remembering and orally passing down the culture’s history 

• Individual knowledge 

  • Greater access to information 

  • Better ability to convey one’s own thoughts 

  • New ability to build on established knowledge and ideas

• Creativity 

  • Writing facilitated a new creativity (and still does)

  • We read the writings of others, and we create from there 

• The creation of the Greek alphabet was followed by one of the most prolific periods of writing, art, philosophy, theater, and science in all previously recorded history

Resistance to Change 

• But the Greek alphabet took almost 400 years to gain acceptance because of:

  • Adherence to their oral traditions 

  • Worries about how it might negatively affect the masses

Differences in Brain Activation 

• Some languages (e.g., Chinese, Japanese Kanji) use logographic characters–depicting words or word parts instead of individual sounds 

  • Readers are required to memorize each symbol rather than word-sound associations 

  • These alphabets activate the right hemisphere to a relatively greater degree

Ease of Learning the Alphabet

• There are cross-cultural differences in how well phonemes (sounds) map onto graphemes (words)

• In English, spelling rules are relatively complicated 

• About 45 speech sounds that map onto 26 letters 

  • Many sounds need to be indicated by a combination of letters 

• Spelling is complicated 

  • It gives clues to meaning 

    • I and eye 

    • You and ewe 

    • To, too, two, and stew 

  • It shows a word’s root 

    • “Muscle” retains a c to reflect its Latin root “musculus” and its relationship to other words (e.g., “muscular”, musculature”)

• In Italian, the sounds made by letters are relatively consistent and predictable 

• Only about 30 speech sounds that map onto 21 letters 

• Learning to read happens much more quickly and with less effort 

• Dyslexia is experienced much less often 

Proto-Letters 

• The monkey’s brain is made up of neurons that respond to different fragments of shape, whose combination can describe any complex form

• Proto-letters are basic shapes that constitute a generic “alphabet” that can be combined to make up any natural scene

• Proto-letters are non-accidental shapes because they are unlikely to occur accidentally 

  • If you threw a bunch of matches on the floor, you would be unlikely to see these distinct shapes form

• Tend to be places where surfaces join 

• Cues the visual system, they are likely a part of an object present in the outside world 

• This is what has been recycled to account for our human ability to learn an alphabet of symbols!

Non-accidental Properties 

• Our memory doesn’t store fully detailed images of objects 

• Instead, it extracts the non-accidental properties and their spatial orientation in relation to each other 

• If non-accidental properties are preserved, identification of the object is pretty easy

• If the non-accidental properties are deleted, it becomes harder!

• When the non-accidental properties are in place, our brains can’t help but to see it as a coherent, whole object!