Learning New Things

“Barring some catastrophic planetary nightfall, the tech industry will create within decades, machines with human-level intelligence and behaviors capable of speech, reasoning, highly coordinated actions in economics, politics and, inevitably, warcraft.  The birth of true artificial intelligence will profoundly affect humankind’s future, including whether it has any.”

Christof Koch

            So far we have been looking at times when changes in how we communicate led to changes in how the brain handles information.  We have looked at the development of speech, writing, and printing.  It might be worthwhile to look in more detail at how the brain has changed and to consider what might be in store for it going forward.  This is a bit complicated, so I will divide it into two posts to keep it manageable. Here is part one.

            Speech is a special case because 50-60,000 generations have allowed time for genetics to take over.  Hominin brains are vastly different from those of chimpanzees, our nearest primate relatives; our brains are four times as large and our thinking lobes have orders of magnitude more neurons. Neanderthal brains reached their maximum size about 600,000 years ago and had a genetically determined increase in the number of their frontal lobe neurons.[1] Mutations made the brain capable of speech and the ability to imagine the future, both of which are unique to humans. It is an odd side note that brain size peaked in those Neanderthals at 1,459 ± 182 cubic centimeters while modern human brains average only 1,328±145 cubic centimeters. The decrease in brain volume came only about 3-5,000 years ago—after speech but roughly coincident with the development of writing.  Our brains have either become more efficient or they lost something about the time we acquired the new technology.

            What happens in the brain when people learn to speak?  Although no one is born knowing how to talk, small children—even those with significant intellectual impairment—acquire the skill with astonishing rapidity.  Between ages two and five, children learn an average of two to four new words a day. The average five-year-old has a 10,000-word vocabulary that will grow to about 88,700 words during subsequent school years. Early childhood is the only time we can become fluent in a language (or occasionally more than one) in such a short period.  Noam Chomsky argues that is because humans are born with grammar somehow coded into our brains by a genetic change that occurred 50 or 60,000 years ago.  Most scientists think it is more likely that anatomic changes associated with speech  (for example a tongue designed to handle food adapting to manipulate sounds) slowly developed over one or two million years.

            Regardless, the brain changed dramatically as half of it became inextricably linked to speech.  The angular gyrus sits at the junction of the parietal, occipital, and temporal lobes where it is uniquely situated to bring together tactile, auditory, and visual inputs.  The major sensory inputs are processed and merge in the angular gyrus which has been justifiably called the integrator of integrators. In 1874 twenty-six-year-old Carl Wernicke proved that damage to the left angular gyrus rendered the victim unable to produce comprehensible speech, and Joseph-Jules Déjerine subsequently found that the damage to the same area led to the loss of the ability to read and write.  Language lives in the dominant angular gyrus.

            We cannot leave without briefly considering what was happening in the non-dominant half of the brain.  In the years before PET scans and functional MRI’s, I remember doing Wada tests to be absolutely sure which hemisphere was responsible for speech before surgery on the brain, and that led to some interesting insights.[2]  In the Wada test, a catheter is put in the carotid artery and a short acting anesthetic injected.  If the artery feeds the dominant hemisphere, the patient temporarily loses the ability to talk.  The interesting thing is that a fair number of those patients retain the ability to sing with the lyrics intact—words associated with music evidently coming from the non-dominant side.

            In the early 1960s Canadian neurosurgeon Wilder Penfield experimented on more than 500 patients undergoing operations most of which were designed to remove areas of damaged brain responsible for intractable seizures.  Because the brain itself has no sensation, Penfield was able to operate with the patients awake; he could electrically stimulate various parts of the brain during the procedures and observe the results.  Stimulation of the parietal, occipital, and temporal areas on the non-dominant side could produce vivid somatosensory, visual, or auditory hallucinations.  Remember Julian Jaynes and the loss of the gods?  Hallucinations seem to be a non-dominant talent, an observation that you might recall was recently verified with functional MRIs in actively hallucinating patients.

            For our purposes the important thing is that, over hundreds of thousands of years, the human brain structurally changed to allow it to communicate with words and symbols, and those changes were coded into our DNA and pass from generation to generation.

            Writing is different.  In the first place, unlike speech, there is direct historical evidence of how literacy changes the brain.  Second, the changes wrought by literacy occurred over a few thousand years, not tens of thousands of generations.  There has not been enough time to code the changes into our genes; writing cannot be handed down from one generation to the next.  The brain changes associated with writing all must be learned—they are the changes of training, not heredity.

            Nonetheless, writing does change the brain.  Non-literate communication is almost entirely auditory whereas reading uses the visual brain.  Literacy moves information processing from the auditory temporal lobe to the frontal lobes and from the non-dominant to the dominant hemisphere. Areas that were genetically designed to recognize and name objects are re-programmed to recognize letters and words.  Groups of trained neurons recognize written language and associate it with memory so quickly that it is automatic.  We read without thinking about it, but reading starts as a learned skill.

            The learning has not always been pleasant.  The oldest examples of teaching reading we have are Sumerian clay tablets with a teacher’s example on one side and the student’s attempt to reproduce it on the other.  The school days were long and learning the thousands of cuneiform characters was a burdensome chore.  The schools had a “man of the whip,” and the last words on a student tablet were often, “And then he caned me.”

            The cuneiform example brings up an interesting point.  In assigning literacy to the dominant side of the brain, we have been tacitly assuming we were talking about characters that represent sounds.  Remember in cuneiform and some Eastern writing most characters represent not a sound but a thing.  You might guess that would affect lateralization, and you would be right.  Readers of Chinese ideograms recruit brain areas across both hemispheres.  Japanese is even more interesting.  It has two writing systems—kana which is phonetic and handled with the dominant hemisphere, and kanji which uses ideograms and draws on both sides. A patient with a unilateral brain lesion can lose one type of writing but retain the other.

            This is a good place to stop for now, but there are two main things to remember.  First, the brain does physically change with acquisition of communication skills.  Second, the change can be either inborn or learned, although the genetic changes take a very long time.  In the next post we will look at the changes when information exploded and at what is happening now and might happen in the future.

References

Geschwind, Norman, Selected Papers on Language and the Brain. Boston: D. Reidel Publishing Company, 1974.

Wolf, Maryanne, Proust and the Squid: The Story and Science of the Reading Brain. New York: HarperCollins Publishers, 2007.

Wolf, Maryanne, Reader Come Home: The Reading Brain in the Digital World. New York: HarperCollins Publishers, 2020.

[1] Of about 19,000 hominin genes, only 96 have been identified that separate Neanderthals from modern humans.  One of these is responsible for producing transketolase-like protein 1 (TKTL1) that, in the laboratory setting, does increase neuron production.

[2] Almost all—but not every—right-handed person is left dominant, and half of left handers are as well.