The Knowing Hand: The Inferior Parietal Lobule and the Evolution Of Reading, Writing, & Arithmetic

The Knowing Hand: The Inferior Parietal Lobule & The Evolution Of Reading, Writing, & Arithmetic
Rhawn Gabriel Joseph, Ph.D.


It is now well known that among over 80% of the right handed population, and 50% of those who are left handed, the left cerebral hemisphere provides the neural foundations for the comprehension and expression of grammatically complex spoken language. The left half of the brain dominates in the perception and processing of real words, word lists, rhymes, numbers, Morse code, consonants, consonant vowel syllables, nonsense syllables, the transitional elements of speech, and single phonemes. It is also dominant for recognizing phonetic, conceptual, and verbal (but not physical) similarities; for example, determining if two letters (g & p vs g & q) have the same vowel ending 1.

The neocortical mantle of the left half of the cerebrum mediates most aspects of expressive language functioning such as reading, writing, speaking, spelling, naming. This includes the comprehension of the grammatical, syntactical, and descriptive components of language, as well as time sense, rhythm, verbal concept formation, analytical reasoning, and verbal memory 2.

Perceiving, organizing, and categorizing information into discrete temporal units or within a linear and sequential time frame are also left hemisphere dominated activities. Indeed, the left half of the brain is sensitive to rapidly changing acoustics be they verbal or non-verbal. It is also specialized for sorting, separating and extracting in a segmented fashion, the phonetic and temporal-sequential or articulatory features of incoming auditory information so as to identify speech units 3.


The left cerebral hemisphere is specialized in regard to the temporal-sequential control over hand movement as well as perceiving and expressing units of information in regard to sequences. In fact, language and the production of verbal thoughts are related to and in part are an outgrowth of left hemisphere mediated motor activity 4. This is why individuals often gesture with the right hand when they speak and why injuries to the left half of the brain disrupt the performance of actions requiring a set series of sequences, i.e., apraxia.

Temporal-sequencing is of course a fundamental property of language as demonstrated by the use of syntax and grammar. That is, syntax is a system of rules which govern the positioning of various lexical items and their interrelations to one another. This allows us to do more than merely name but to describe and to analyze how various parts and segments of speech interrelate. We can determine what comes first or last (e.g. "point to the door after you point to the window"), and what is the subject and object. When the left hemisphere is damaged, expressive and receptive aspects of syntactical information processing suffer.

In contrast, the right half of the brain has great difficulty utilizing syntactical or temporal-sequential rules 5. In studies of individuals who have undergone the surgical separation of the two cerebral hemispheres (i.e. split-brain operation), when the isolated right brain is given a command, such as "pick up the yellow triangle after you pick up the blue star", it will simply (via the left hand) pick up the yellow triangle. The right brain responds to the first item in the sentence regardless of grammatical relationship 6. In fact, the ability of the right half of the brain to understand vocabulary and the denotative aspects of language is also limited to emotional words, melody, singing, mimicry, and just a few concrete words.

The reason that only the left half of the brain is able to understand and perform a simple task such as the above, whereas the right half is unable to do so, is because the ability to extract denotative meaning from complex spoken language is dependent on the ability to organize and coordinate speech into temporal and interrelated units. This is a function at which the left hemisphere excels, and an ability which is at least in part strongly related to the predominate usage of the right hand for repetitive sequential activities for much of human history 7. Among the majority of the population, motor control in turn is dominated by the right hand. Hence, the left parietal lobe would be the more neurologically wired to perform these actions as compared to the right parietal region which (in conjunction with the right frontal motor area) mediates left hand functioning.


There is considerable evidence that the grammatical and syntactical components of spoken language, are directly related to handedness and the evolution of the left inferior parietal lobule. Among the majority of the population it is the right hand which is dominant for grasping, manipulating, exploring, tool making, sewing, writing, creating, destroying, and communicating. Although the left hand assists, it is usually the right which is more frequently employed for orienting, pointing, gesturing, expressing and gathering information concerning the environment. We predominantly use the right for activities such as throwing, hitting, writing, drawing, and so on, and are more likely spontaneously to activate the right rather than the left half of the body. While engaged in non-emotional, explanatory, or descriptive speech most individuals are more likely to gesture with the right arm and hand which appears to accompany and even emphasize certain aspects of speech 8. Hence, the right hand appears to serve as a kind of motor extension of language and thought insofar as it often accompanies or acts at the behest of linguistic impulses.

Given the preponderance of right hand activity while talking or gesturing, it is apparent that gesture, like speech, is linked to the functional integrity of the left half of the brain and that both share or are tightly interlinked with some of the same neurons that support speech activity 8. In fact, immediately above the neocortical frontal lobe motor areas where the neurons which represent muscles of the face and mouth are located, can be found neurons which represent the hand, and Broca's expressive speech area is adjacent to both. This same close proximity is maintained in the sensory areas of the parietal lobe which in turn are tightly interlinked to the frontal neocortical motor area via extensive axonal-dendritic interconnections.

When one speaks, due to the spreading of excitation to neighboring groups of cells, hand neurons become excited as well including those involved in controlling the muscles of the mouth. Hence, speaking triggers hand movement. Conversely, as is evident from working with the deaf, signing also often triggers sound production. The deaf often make sounds while signing because presumably activation of those neurons involved in hand control and gesturing stimulate neurons involved in vocalization. As in normally speaking adults, the neurons subserving both functions are adjacently located.

Because the hand and speech area partially occupy closely adjacent neuronal space, when both are simultaneous activated there results competitive interference. While speaking the ability to simultaneously track, manually sequence, or maintain stabilization of the arms and hands is concurrently disrupted 9. In addition, as the phonetic difficulty of the verbalizations increase, motor control decreases--a function presumably of simultaneous activation of (and thus competition for) the same neurons.

Motor functioning, however, is dependent on sensory feedback which in turn is provided by the parietal lobe 10. That is, if not for the sensory feedback provided by the muscles and joints, information which is transmitted to the parietal lobes, movement would become clumsy and incoordinated since a person would not know where their limbs were in space and in relation to one another. Since the parietal lobes and the motor areas in the frontal lobes are richly interconnected, they serve in many ways as a single neurocortical unit, i.e. sensorimotor cortex.

It is in part due to this interrelationship between sensory feedback, motor control and gesture, that language production is greatly dependent on the parietal and frontal lobes where the motor centers and Broca's speech area are located. Although language serves to question and describe, initially it is through touch that one first comes to know the world. Knowing is first made possible via the hand which in turn initially, during the early stages of development, tends to pick up everything within reach and place it in the mouth where it is then orally explored (a function of the immature amydala). Hence, the hand and the mouth are linked almost from the outset in regard to the acquistion of knowledge. Nevertheless, be it a human infant, or an adult ape, it is the hand which is first employed for the purposes of information gathering and classification.


As noted, the parietal lobe is sensitive and responsive to tactual stimuli regardless of where on the body it is applied. In fact, it is via the reception of these signals from the sensory surface of the body, that the entire body comes to be spatially represented in the neocortex. However, body parts are represented in terms of their sensory importance, i.e. how richly the skin is innervated 12. For example, more cortical space is devoted to the representation of the fingers and the hand than to the forearm as there are more sensory receptors located in these regions of the skin. Because of this the neocortical body map is very distorted and the hand receives extensive representation.

When tactile sensations are transmitted from the body surface to the amygdala and thalamus, and finally to the primary receiving areas for somosthesis (e.g. body sensations), located within the neocortex of the parietal lobe, one is able to determine not only the qualities of the object being touched (e.g. hard, round, wet, sharp, heavy, pitted) but what part of the body is being stimulated (e.g. hand, elbow, foot). It is within the parietal area of the brain where conscious perceptual tactual associations are formed.

It has been said that the parietal lobule is an organ of the hand 13. As noted, the hand appears to be more extensively represented than any other body part, and parietal neurons mediate temporal-sequential hand control, and become highly activated in response to objects which are within grasping distance 14.

It is also by the hand that the parietal lobe gathers information regarding various objects (stereognosis), and about the Self and the World, so that things and body parts come to be known, named, and identified. Ontogenetically, the hand is in fact primary in this regard. The infant first uses the hand to grasp various objects so they may be placed in the mouth and orally explored. As the child develops, rather than mouthing, more reliance is placed solely on the hand (as well as the visual system) so that information may be gathered through touch, manipulation and visual inspection. It is at this stage where still immature parietal lobe neurons begin to join the amygdala in information acquisition.

As the child and the neocortex of its parietal lobe mature, instead of predominantly touching, grasping, and holding, the fingers of the hand are used for pointing and then naming. It is these same fingers which are later used for counting and developing temporal-sequential reasoning; i.e. the child learns to count on his or her fingers, then to count (or name) by pointing at objects in space. It is at this point that the latest and slowest region of the brain to mature, the inferior parietal lobule, begins to play an increasing role in cognitive development.

Counting, naming, object identification, finger utilization, and hand control are ontogenetically linked and all seem to rely on the same neural substrates for their expression; i.e. the left inferior parietal lobule. Hence, when this portion of the left hemisphere is damaged, naming (anomia), object and finger identification (agnosia), arithmetical abilities (acalculia), and temporal-sequential control over the arms and hands (apraxia) are frequently compromised 15.

Hence, a variety of symptoms are associated with left inferior parietal lobe damage. However, when this particular constellation of disturbances, i.e. finger agnosia, acalculia, agraphia (loss of the ability to write), and left-right disorientation, occur together, they have have been referred to as Gerstmann's syndrome 16. Gerstmann's symptom complex is most often associated with lesions in the area of the inferior and superior parietal lobule. However, because this symptom complex does not always occur together, some authors have argued that Gerstmann's syndrome, per se, does not exist.

We will not take issue, pro or con on this minor controversy but instead will focus on those aspects of Gerstmann's syndrome which have not yet been discussed (finger agnosia, acalculia, left-right disorientation).


Finger agnosia is not a form of finger blindness , as the name suggests. Rather, the difficulty involves naming and differentiating among the fingers of either hand as well as the hands of others 17. This includes pointing to fingers named by the examiner, or moving or indicating a particular finger on one hand when the same finger is stimulated on the opposite hand, or if you touch their finger while their eyes are closed, and ask them to touch the same finger they may have difficulty.

This may not seem like a terribly disabling disorder. However, when one considers the importance of the hand and especially the fingers in exploring an object in order to comprehend its character and potential, finger agnosia, particularly if it occurs in a child, can drastically reduce and interfere with the very foundations of knowledge acquisition.


By time a child has reached the age of three she is capable of making simple calculations and this is a function of the early stages of maturation of the inferior parietal lobe. Counting is important in knowledge acquisition because it aids in the ability to determine what is, versus what isn't, and thus to form categories consisting of abstract notions. The ability to count requires and relies on the ability to make fine distinctions and to differentiate not only what is "4" versus "eight," but to classify so as to determine what is four apples versus 8 bananas, and how that adds up to a dozen pieces of fruit.

When the parietal lobe has been injured, or is slow to mature, an individual may in consequence have problems not only in classifying, but in adding and subtracting 18. How this problem manifests itself depends on whether the right versus left parietal lobe has been injured.

A individual with a right parietal disturbance, when performing arithmetical operations may misalign numbers when adding or subtracting (referred to as spatial acalculia). With left (or right) parietal injuries he may erroneously substitute one operation for another, i.e. misreading the sign "+" as "x", such that he multiplies rather than adds. Or he may reverse numbers i.e. "16" as "61", substitute counting for calculation, i.e. 21 + 6 = 22, or inappropriately group: 32 + 5 = 325.

On the other hand, with injuries localized to the vicinity of the left inferior parietal lobe, patients may have severe difficulty performing even simple calculations, e.g. carrying numbers, stepwise computation, barrowing and they may in fact be unable to recognize numbers. For example, they may be unable to write out or point to the number "4" vs the number "8" vs the letter "B". Hence, in some cases it is the spatial nature and in others it is the temporal sequential deficit and the ability to recognize or write out abstract signs and symbols which causes them difficulty.


When reading and writing, or when performing gestures involved in the production of ASL, the ability to correctly orient oneself and one's movements and perceptions in regard to right versus left and up versus down, is very important. Gestures are made in space, and the movement of the hands in space is made possible via the parietal lobes. Hence, when this structure is injured, the ability to orient to the left or the right may be impaired 20. Nevertheless, although the right half of the brain is clearly dominant in regard to analyzing and expressing spatial relationships, it is the left half which is concerned with the temporal sequential aspect of movement in space, including orientation to the right or the left 19.

In part, it seems somewhat odd that right-left spatial disorientation is more associated with left rather than right cerebral injuries, given the tremendous involvement the right half of the brain has in spatial synthesis and geometrical analysis. However, orientation to the left or right transcends geometric space as it relies on language. That is, "left" and "right" are designated by words and are defined linguistically. In this regard, left and right become subordinated to language usage and organization. Hence, left-right confusion is strongly related to problems integrating spatial coordinates within a linguistic framework.

It is for this reason that when the left parietal lobe has been injured, an individual who is proficient in ASL may become aphasic for signs. They may lose not only the ability to comprehend them but to make them appropriately. However, if they were able to speak and converse before their injury, they retain these abilities although they can no longer sign.

Right left orientation is vital not only in the production of signs and gestures, but in the evolution of reading and writing.


The development and acquisition of language seems to be related to manual gesturing and fine motor exploration, complex sequential processing, and the ability to form concepts and to classify a single stimulus in a multiple manner. For example, classifying and labeling a chair according to the type of fabric, cost, color, comfort, style, and to describe it as such using words. Or, conversely, hearing the word "chair" and being able to consider it from multiple perspectives. This is made possible via the inferior parietal lobe 20.

The development and evolution of the inferior parietal lobule enabled complex gestures to be learned and performed. Through its rich interconnections with the immediately adjacent neocortical areas in the temporal lobe which are responsible for the perception of sound, the inferior parietal lobe is also able to impose and stamp temporal sequences on auditory input and thus break it up into units . This includes sounds that are transmitted to it from the auditory (Wernicke's) association areas located in the immediately adjacent superior and middle temporal lobe of the left hemisphere. This relationship in part also made possible the development of grammar.

The acquisition and expression of complex grammatically correct spoken language is not dependent only on grammar but the ability to develop and assign labels and multiple categories so that what was heard could be quickly analyzed for meaning. Again, in order to comprehend that the word "chair," indicates an object that you can sit in, the person must be capable of associating completely different sensory experiences into an interlinking category so that multiple possible meanings can be assigned and extracted. It is in this manner that we come to know what words may signify as well as their grammatical relationship. Otherwise a sound would be merely a sound having little more than emotional or motivational significance.

This ability to form multiple categories and to impose grammatical structure on all that is said, is made possible by the same structure which provides temporal sequencing to movement and which guides and controls the ability to gesture and perform complex actions. The inferior parietal lobule and the angular gyrus 21.


Developmentally, of all cortical regions, the inferior parietal lobule is one of the last to functionally and anatomically mature in terms of function and anatomy 22. In this regard, ontogeny replicates phylogeny in that humans are the most recent species to appear on this planet and the only one to possess an angular gyrus of the inferior parietal lobe. It is due to its slow maturation that many capacities mediated by this area (e.g. reading, calculation, the performance of reversible operations in space) are late to develop appearing between the ages of 5-8. Because humans are the only species to possess this neocortical region, no other animal is capable of these cognitive feats.

The inferior parietal lobule contains many hundreds of millions of neurons most of which are multimodally responsive. A single neuron may simultaneously receive highly processed somesthetic, visual, auditory and movement related input from the neocortical association areas located in the parietal, occipital, temporal, and frontal motor areas. Hence, many of the neurons in this area are multi-specialized for simultaneously analyzing auditory, somesthetic, and spatial-visual associations, have visual receptive properties which encompass almost the entire visual field, and respond to visual stimuli of almost any size, shape, or form 23 .

Due to their extensive interconnections with the adjacent neocortical area, inferior parietal neurons are able to assimilate and create multiple associations. The inferior region thus acts to increase the capacity for the organization, labeling and multiple categorization of sensory-motor and conceptual events. One can thus create visual images, somesthetic, or auditory equivalents of objects, actions, feelings, and ideas, simultaneously, and can conceptualize a "chair" as a word, visual object, or in regard to sensation, usage, and even price. Similarly, when we see an object such as a chair, we are then able to name it.


Because of its involvement in functions such as those described above, one effect of damage to the left angular gyrus is a loss of the ability to correctly name things, or to find words; a condition called anomia. Patients so affected cannot recall the names of things even when looking right at them such that the words they search for seem to be perpetually on the "tip of the tongue." However, this condition is much worse for if told the word they immediately lose it again. These individuals have difficulty naming objects, describing, pictures, etc.

On the other hand, if the area of tissue destruction is quite circumscribed so that the inferior parietal lobe is disconnected from just one adjacent neocortical area, for example, the visual cortex, the loss of naming ability will be only for things the person looks at, though it could be named if described verbally or felt in the hand. If instead the damage disconnected the inferior region from the rest of the upper parietal lobe, then they would be able to name the object if they looked at or heard it but not if they just felt it in their hand 24. These are called disconnection syndromes.

Moreover, lesions involving the angular gyrus, or when damage occurs between the fiber pathways linking the left inferior parietal lobule with the visual cortex, there can also result Pure Word Blindness and the person loses the ability to read words or sentences. This is due to an inability to receive visual input from the left and right visual cortex (located in the occipital lobe). Although these people can see without difficulty they are unable to recognize verbal symbols, such as words and even letters because this information is no longer linked up with Wernicke's area and the inferior parietal lobule. Like anomia, pure word blindness is due to an inability to transmit visual-linguistic information to Wernicke's area so that auditory equivalents may be called up. This is due to disconnection. One can no longer link or match the sound or verbal name to the visual image and can no longer read 25.

Depending on the extent of the injury some patients may experience only a mild disturbance involving word and letter recognition and this is referred to as dyslexia as they have difficulty reading. Dyslexia, however, can result from a number of conditions including the slow or incomplete maturation of the inferior parietal lobe. Those who are completely unable to read and recognize words are described as suffering from alexia.

The inferior parietal lobe acts not only to assimilate different associations but to relay this information via a bundle of axons (called the arcuate fasciculus) to Broca's expressive speech area in the frontal lobe. It is via Broca's area that words come to be articulated.

Destructive lesions involving this axonal fiber pathway between the inferior parietal and Broca's area can result in conduction aphasia 26. That is, the person would know what they want to say and they might even be able to hear the word in their head. However, due to destruction of this fiber pathway the information is cut off from Broca's area and cannot be expressed. Nor would someone so affected be able to repeat simple statements, read out loud, or write to dictation. This is because Broca's area is disconnected from the posterior language zones.


The evolution of the inferior parietal lobule not only made language possible but provided the neurological foundations for tool design and construction, the ability to sew clothes, and the capacity to create art, and pictorial language in the form of drawing, painting, sculpting, and engraving. Finally it enabled human beings to not only create visual symbols but to create verbal one's in the form of written language 27. In fact, with the exception of written language, all these abilities, including, perhaps, spoken language, may have appeared essentially within the same time frame, the first evidence of which is approximately 40,000 years old and was left in the deep recesses of caves and rock shelters throughout Europe and Africa 28.

Although we have no recordings of what people may have sounded like, or any evidence regarding the presence of grammatical sequences in their speech, complex and detailed paintings left in the deep and forgotten recesses of ancient caves indicates that human beings, the Cro-Magnon, were capable of felling stories and making signs which are still comprehensible and pregnant with meaning 40 millinea later. However, it is likely that they were speaking and sharing thoughts and desires since they first appeared on the scene, about 130,000 years ago.

Although we can debate the merits and purposes for which these pictorial displays were created (magic, religious, instructive), they nevertheless represent the first form of written language. Body movements and gestures had now become adapted for reproduction in the form of pictures, the result of well crafted, delicate, and precise finger, hand, and arm movements.

As can be seen based on photographs of Cro-Magnon cave art and that of ancient Egypt, Sumer, and Babylon (about 4,000 to 6,000 years ago), this form of pictorial language remained essentially similar for almost 35,000 years. It is also apparent that although much of what was depicted during this time frame were without any grammatical foundation, that occasionally temporal elements were imposed. For example, on a dollar sized emblem created perhaps 20,000 years ago, there appears a deer standing on one side, whereas on the other the same deer is lying on the ground, either asleep or more likely wounded or dead Hence, art became adapted for not just depicting, but telling a changing story.

In fact, by 15,000 years ago stories regarding the exploits and conquests of humans began to be told in the form of paintings. Specifically, fearsome battles and the stalking and killing of men in combat. In fact, for the following 15,000 years similar stories of mayhem, murder and conquest would be told to eager and receptive audiences, transmitted by satellite and movie screen directly to that ancient limbic tissue that thrives on witnessing and engaging in such acts.

Nevertheless, these first stories, which for the most part concerned killing and conquest, were not present in temporal-sequential dimensions. Rather, as is evident from the "writings" of the ancient Egyptians and the Sumerians, these pictorial displays were very gestalt in formation and arranged in regard to spatial relationships. That is, they were produced in a manner typical of the right half of the brain.

Nevertheless, these ancient stories told are for the most part comprehensible 6,000 years later by people from wholly different cultures and who speak completely different languages, including, I presume, those of you reading this book. The same, of course, was true 6,000 years ago which is what must have made this form of "writing" extremely effective as a communicative device, particularly in an educated society surrounded by the uneducated masses 29 .

Take for instance, this stella erected by an Egyptian pharaoh who probably ruled Egypt around 6,000 years ago (see figures 98, 99). Hence we see at the top the heads of two bulls which symbolize strength and below which are pictures of men, one of whom in particular is quite large and who we might assume is the leader, or a god, or the king. It is apparent that he is marching in procession with many subjects and standard bearers and that many men were decapitated in consequence.

Below that we see two giant, long necked leonine creatures who have been captured, and below that we see the bull is besieging a city fortress. Looking to the other side we see again a very large man who is wearing a different hat but who otherwise is dressed the same as the first man. Hence, this again must be the king and he is smiting an enemy that has been captured. What this then tells us is that the King of Egypt went to war against and conquered a city and took many captives including this "mythical" lion headed beast which was the symbol of his human foe who happened to live in ancient Sumer.

if perchance we had lived in Egypt 6000 years ago and had some cultural knowledge and a context in which to interpret this stella the story would not change much except that we would know that the city was ruled by ancient Sumer for the captured beasts were a motif popular among the Sumerian royalty.

We would also know that the two crowns worn by this pharaoh stand for upper and lower Egypt, that behind him are his sandal-bearer and foot washer, and that in front are his priest and standard bearers. Since those who are decapitated appear to be Egyptians, it is possible that this king took action against some rebels or perhaps Sumerian soldiers holding a city of Upper Egypt. His success is further indicated by his initially wearing the crown of Lower Egypt only later to replace it with a second crown of Upper Egypt after defeating the Sumerians the corpses of whom lay below his feet. In this regard the stella may in fact tell two stories, one of which concerns the uniting of upper and lower Egypt and the other an attack on the Sumerians. The hawk and rebus above the head of the captive about to be struck basically reads, "Pharaoh the incarnation of the hawk-god Horus, with his strong right arm leads captives."

Who is the pharaoh that is depicted? Some scholars have assigned him the name of King Narmer, others believe him to be king Menes. In actuality it may well be neither and may represents a king who ruled much further back in antiquity than many scholars are willing to consider, i.e. about 6,500 years ago.


When, where, how many times, and how many places the art of writing was invented, know one knows. The earliest preserved evidence detailing the evolution of written symbols comes from ancient Sumer, around 6000 or more years ago. In Sumer as elsewhere, the first forms of "writing" were pictorial, a tradition that was already in use at least 20,000 years before their time.

Indeed, in examining the pictorial representations left by the Cro-Magnon, they, just like modern westernized humans, utilized single pictures, such as a red hand to indicate a clear, readily understood message, such as "stop", or "do not enter." In most American cities, this same "hand" symbol is used at intersections to indicate if and when someone may cross a street. Moreover, the Cro-Magnon also utilized abstract symbols, the meanings of which are not at all clear, though some have associated them with sex, or fertility, or male vs female signs, and so on. However, maybe it too was a primitive form of writing.

However, the Cro-Magnon people also liked to produce art for the sake of art and were the first people to paint and etch what today might be considered "cheesecake." That is, slim, shapely, naked and nubile young maidens in various positions of repose 30.

The Sumerians too initially utilized single pictorial symbols to convey specific messages, sometimes such as a "lion" to indicate "watch out, lions about," or that of a grazing gazelle so as to inform others that good hunting could be found in the vicinity 31 Although the Cro-Magnons sometimes used single two-step pictorial displays to indicate a sequence of action, as based on available evidence, it was not until the time of the Sumerians that people began skillfully to employ a series of pictures to represent not just actions, but abstract as well as concrete ideas.

For example, prior to the Sumerians, a depiction of a lion or a man might indicate the creature itself, or the nature God that was incarnate in its form. The Sumerians took this to its next evolutionary step. For example, by drawing a "foot," or a "mouth," or an "eye," they could indicate the idea "to walk," or to "eat," and to "look" or "watch out." By combining these pictures they were then able to indicate complex messages, such that "so and so" had to "to walk" to a certain place where "gazelles" might be found in order "to eat," but they would have to keep an "eye" out for "lions." 32

This was a tremendous leap, for earlier in Sumerian civilization, just as in Egypt and elsewhere, to indicate a complex message such as the above would have required elaborate pictorial detail of entire bodies engaged in particular actions. Although beautiful to behold, and easily understood by all, this was a very cumbersome and time consuming process.

The next step in the evolution of writing was the depiction not just of actions and ideas, but sounds and names. As argued by Edward Chiera 34, if they wanted to write a common Sumerian name such as "kuraka," they would draw objects which contained the sounds they wanted to depict, such as a "mountain" which was pronounced "kur," and "water" which was read as "a," and then a "mouth" which was pronounced "ka," and by combining them together one was able to deduce the sound or name that the writer desired.

This was a tremendous leap in abstract thinking and in the creation of writing, for now visual symbols became associated with sound symbols and one could now not only look at pictures and know what was meant, but what the symbols sounded like as well. In this manner, writing, although still in pictorial form, became much more precise. Now ideas, actions, and words, and thus complex concepts could be conveyed.

Nevertheless, although this was a highly efficient means of communication, it still remained quite cumbersome which required that further steps in symbolic thought be invented. The Sumerians met this challenge by inventing wedge form cuneiform characters which gradually began to replace the older pictographs and ideographs.

Initially these characters resembled the pictures they were destined to replace. However, as the use of cuneiform continued to evolve, pictorial details were gradually minimized, until finally these characters lost all pictorial relationship to that which they were meant to describe. Among the ancient Egyptians, a similar process occurred with the exception that with the invention of hieroglyphics, pictures remained an essential feature of their writing until the very end of their civilization about 2,000 years ago.

The Sumerians, Babylonians, and the later appearing Assyrians, however, although able to depict vowels, consonants, and complex ideas and sounds via cuneiform, did not develop an alphabet 33. In fact, even when they were introduced to foreign devised alphabets, they resisted this innovation. Even so, pictures came to be placed in temporal sequences, and then the pictures themselves became represented by sequences as well, a series of wedge shaped lines which were read from left to right.

Nevertheless, be it the writing of the Egyptians, the Sumerians, or modern day Americans, the process of reading and writing remains essentially similar. Both require the interaction of brain areas involved in visual and auditory analyses, as well as the evolution of the inferior parietal lobule which enabled visual signals to be matched with sounds so that auditory equivalents could be conjured up. In this manner people are able to not only look at a word but to know what it sounds like.


Maxwell glanced up from his book and the notes he was taking and smiled at the ugly little man who had nervously walked right up to his counter.

"Studying?" the skinny man asked as he reached into his trench coat pocket.

"Yea, got a big test."

"Well, I don't think your going to pass," the man replied as he pulled out a little 25 caliber semi-automatic and shot Maxwell point blank, as he tried to turn away, striking him in the left parietal region of his skull.

When Maxwell woke up in the hospital he immediately felt overcome by a fearsome headache and reaching up he was terribly surprised to find that part of his head was bandaged and most of his hair gone. He was "lucky" though, or so said his doctors. Although the bullet had cracked his skull, it did not penetrate but instead went round and round his head underneath his skin. Moreover, although he had suffered a fracture the doctors felt that the amount of blood that had developed on the inferior parietal lobule of his brain, directly beneath the site of impact, was negligible. To prove this to their satisfaction they asked him a few questions, tested his memory, and then released him the next day as he seemed fine.

But Maxwell wasn't fine. On the way home he noticed that some of the billboards along the roadway didn't make sense, and when his headache subsided enough for him to pick up his school books, he discovered that he couldn't make out any of the words or sentences, nor did any of the letters make sense.

"What's wrong with me?" he asked in panic. Had he forgot how to read? Why did the words look so weird? Picking up a pen he decided to write out a few words just to make sure he hadn't lost his mind. But then, he wavered, his hand poised just above the paper. He couldn't quite remember how to write....


The process of reading involves the reception of visual impulses in the primary visual receiving areas located within the occipital lobe. It is within the visual neocortex where the initial forms of perceptual analyses are initiated. This visual information is next transferred to the immediately adjacent visual association cortex (areas 18 and 19) where visual associations are formed. These visual associations are next transmitted to a variety of brain areas including the inferior parietal and temporal lobe, and Wernicke's area 35. It is in these latter cortical regions where multimodal and linguistic assimilation take place so that the auditory equivalent of the visual stimulus may be matched and retrieved. That is, via these interactions visual grapheme clusters become translated into phonological sound images. In this manner we know what a written word looks and sounds like. It is also possible, however, to bypass this phonological transcoding phase so that word meanings can be directly accessed (i.e. lexical reading).

Although it is likely that most individuals utilize both lexical and phonological strategies when reading, in either case the the angular gyrus of the inferior parietal lobule is involved. As noted, with lesions involving the angular gyrus, or when damage occurs between the fiber pathways linking the left inferior parietal lobule with the visual cortex (i.e. disconnection), a condition referred to as Pure Word Blindness sometimes occurs. Patients can see without difficulty, but are unable to recognize written language. Written words evoke no meaning because their auditory equivalents cannot be retrieved due to destruction of the interlinking fiber pathway.

There are, however, several subtypes of reading disturbances which may occur with left cerebral damage. These include literal, verbal, and global alexia, and alexia for sentences 34. In addition, alexia can sometimes result from right hemisphere lesions, a condition referred to as Spatial Alexia. All these disorders, however, are acquired and should be distinguished from developmental dyslexia which is present since childhood.

Spatial alexia is associated predominantly with right hemisphere lesions. In part this disorder is due to visual-spatial abnormalities including neglect and inattention. That is, with right cerebral lesions the patient may fail to read the left half of words or sentences, and may in fact fail to perceive or respond to the entire left half of a written page.

Right parietal-occipital injuries may also give rise to spatial disorientation such that the patient is unable to properly visually track and keep place, their eyes darting half hazardly across the page. For example, they may skip to the wrong line. Spatial alexia may also result from left cerebral injuries in which case it is the right half of letters, words and sentences which are ignored.


Just as one theory of reading proposes that visual graphemes are converted into phonological units (visual images into sound), it has been proposed that in writing one transcodes speech sounds into grapheme clusters, i.e. a phoneme to grapheme conversion. In the lexical route, there is no phonological step. Instead the entire word is merely retrieved.

Regardless of which theory one adheres to, it appears that the angular gyrus plays an essential role in writing. Indeed, it has been argued that the sensory motor engrams necessary for the production and perception of written language are stored within the parietal lobule of the left hemisphere 35. Hence, when this part of the brain has been injured, patients sometimes have difficulty writing and forming letters due to an inability to access these engrams; i.e. they suffer from agraphia, an inability to correctly perform the gestures necessary to form written letters or to even gain access to these symbols due to disconnection of the inferior parietal lobe from adjacent cortical tissue 36.

Presumably the angular gyrus provides the word images (probably via interaction with Wernicke's area) which are to be converted to graphemes. However, it is possible that the initial graphemic representations are formed in the inferior parietal lobule. Nevertheless, these representations are then transmitted to the Broca's expressive speech area and adjacent Exner's writing area for grapheme conversion and motoric expression in the form of writing.

Thus, it appears that there are at least two stages involved in the act of writing, a linguistic stage and a motor-expressive gestural stage. The linguistic stage involves the encoding of information into syntactical-lexical units. This is mediated through the angular gyrus and Wernicke's area which provides the temporal sequential and linguistic rules which subserve writing.

The motor-gestural stage is the final step in which the expression of graphemes is subserved. This stage is mediated presumably by Exner's writing area (located in the left frontal lobe above Broca's area) in conjunction with the inferior parietal lobule. Exner's writing area sits immediately adjacent to the primary motor area that controls hand movement as well as Broca's expressive speech area.

Hence, disturbances involving the ability to write can occur due to disruptions at various levels of processing and expression and may arise secondary to lesions involving the left frontal or inferior parietal cortices. Thus, similar to alexia, there are several subtypes of agraphia which may become manifest depending upon which level and anatomical region is compromised. These include Frontal Agraphia, Pure Agraphia, Alexic Agraphia (the condition that Willard suffered following his injury), Apraxic Agraphia, and Spatial Agraphia 37.


Within a small area along the lateral convexity of the left frontal region lies Exner's Writing Area. Exner's area appears to be the final common pathway where linguistic impulses receive a final motoric stamp for the purposes of writing. Exner's area, however, also seems to be very dependent on Broca's area with which it maintains extensive axonal interconnections. That is, Broca's area acts to organize impulses received from the posterior language zones and relays them to Exner's area for the purposes of written expression.

Lesions localized to Exner's area have been reported to result in disturbances in the elementary motoric aspects of writing, i.e. Frontal Agraphia. In general, with frontal agraphia, grapheme formation becomes labored, uncoordinated, and takes on a very sloppy appearance. Cursive handwriting is usually more disturbed than printing and there are disturbances in grapheme selection and the patient may seem to have "forgotten" how to form certain letters. Or they may abnormally sequence, that is, write letters out of order, or even add unnecessary letters when writing. In general patients are unable to write because the area involved in organizing visual-letter organization (i.e. the inferior parietal lobe) is cut off from the region controlling hand movements in the frontal lobe In addition, Frontal Agraphia can result from lesions involving Broca's area. When Broca's area is compromised patients cannot speak or write. When Broca's area is spared, but Exner's area has been damaged, then they can speak but cannot write.

Spatial Agraphia. Right cerebral injuries can secondarily disrupt writing skills due to generalized spatial and constructional deficiencies. Hence, words and letters will not be properly formed and aligned even when copying. There may be difficulty keeping lines straight and letters may be slanted at abnormal angles. In some cases the writing may be reduced to an illegible scrawl.

In addition, patients may write only on the right half of the paper such that as they write, the left hand margin becomes progressively larger and the right side smaller. If allowed to continue patients may end up writing only along the edge of the right hand margin of the paper.

Patients with right hemisphere lesions may tend to abnormally segment the letters in words when writing cursively (i.e. cu siv e ly ). This is due to a failure to perform closure and form a single gestalt, as well as a release over the left hemisphere (i.e. left hemisphere release). That is, the left acting unopposed begins to abnormally temporally-sequence and thus produce segments unnecessarily.


Three hundred thousand years ago a somone took a piece of red ocher pigment and sharpened it presumably so as to mark something 38. On what surface did it draw and what the nature of the composition may have been, we do not know. We can only guess that it served some symbolic purpose, or it may have merely served only to make a mark.

Three hundred thousand years ago someone took the rib of an ox and carved a series of geometric double arches on it 39. Was he or she just doodling, or was this a common form of artistic expression even in those lost days and forgotten nights? Again, we do not know.

Sixty thousand years ago Neanderthals were painting their caves red and by time they were overrun by the Cro-Magnon people twenty thousand years later, geometric patterns, designs and doodles soon graced many a wall 40. However, it was not until about twenty thousand years ago that people began leaving specialized, sequential marks on rocks and walls that suggested that may have been keeping track of, or counting something. Perhaps the phases of the moon, or the number of animals killed? No one knows.

Just as we have no idea when the first complex sentence was spoken, or the first words were written, the point at which human beings first began to count or to measure the geometric properties of the land or the universe surrounding remains a mystery.

Geometry and the first forms of spoken and written pictorial language appear to be naturally related to the functional integrity of the right half of the brain. Conversely, however, it is likely that the first mathematical concepts were promulgated by the left cerebral hemisphere, and like writing, were related to hand use. That is, one first counts on his or her fingers and then they learn to count by pointing with their fingers at that which they wish to sum, and then later they grasp a pen or pencil and make marks and signs which indicate the numbers they used and their summations.

The decimal system is clearly an outgrowth on this reliance on our digits, for this system is based on the concept of tens. Even the decimal systems employed by the ancients of Meso-America was digitalized, with the exception that they used a base of 20 as they apparently counted their toes.

It has been postulated that human beings first became concerned with geometry and numbers with the advent of agriculture (around ten thousand years ago, after the last great flood), as apparently they wished to count their crops as well as survey their fields. However, geometry may well have first been employed to survey the heavens. It was for these reasons that many of the ancients considered geometry to be the math of the gods and of divine origin. Perhaps this is why almost all ancient temples and buildings were oriented in regard to certain celestial configurations, including those of ancient Sumer. The Sumerians were knowledgable about complex geometric principles.

Although it is apparent that the Sumerians were also familiar with and utilized a decimal system, and by 4000 years ago the Babylonians had developed the fundamental laws of mathematics, both cultures nevertheless, relied on a sexagesimal system for their complicated calculations because it was far superior to the decimal 41. For example, whereas the decimal system can be factored by 2,5,10, the 60 unit sexagesimal system could be factored by 2,3,4,5,6,9,10,12,15, and so on.

However, this system, like the first forms of writing was also presumably based on right hemisphere mental functioning as it is this half of the brain which is dominant in regard to the understanding of geometry and the constructive, gestalt and pictorial elements of art.

The sexagesimal system is also clearly related to the geometry of space and the cosmic, or divine circle divided by the equally devine four quadrants of the universe, e.g. North, East, West, South; which in turn forms the sign of a "cross." This is the same cross that most cultures have also deemed to be devine and celestial in origin.

A circle can be divided into 360 degrees. An individual or object sitting opposite is 180 degrees away, half a circle. Hence, via the complicated permutations made possible via the sexagesimal system, the Sumerians, the Babylonians, the Egyptians, the Greeks, and those living in ancient Meso-America were able to make very precise calculations of angular, object, and mathematical relations, and to create temples and buildings, the likes of which today could only be designed, built and fitted together using extremely precise tools and advanced, computerized measuring devices.

It is this same sexagesimal system that is employed in the measurement of time; i.e. 60 seconds and 60 minutes. Similarly, the first calendars were created in the same manner, the Sumerians dividing the circle into 12 parts in accordance with their beliefs regarding the sacred celestial nature of the number "12."

That is, the Sumerians and the Babylonians were well aware that the sun, and not the Earth, was at the center of the solar system. They also realized that the Earth was one of several planets and that all traveled around the sun. As is evident from the engraving shown below, they postulated the presence of 10 planets (one of which may have been a moon), plus the moon that circle the Earth, which, when coupled with the sun, equalled the sum of 12.

Somehow, this knowledge as to the planetary composition and structure of the solar system was lost to subsequent generations as the existence of planets beyond Jupiter and Saturn have only been rediscovered in the last century. Scientists are still searching for the elusive tenth planet that some believe exist outside the orbit of Pluto, or which may have once orbited between the Earth and Mars. It was only a few centuries ago that the Pope and the Catholic Church ordered Galileo to recant his pronouncements regarding the suns central position in the solar system, rather than the Earth, and to destroy his telescopes or face a public burning at the cross for Hearsay .

It is this same Sumerian "12" which makes the 12 hours of the day and the night (the 24 hour day), and is retained in the form of the 12 months and the 12 houses of the Zodiac. The ancient Egyptians essentially adapted this system for designing their own calendar, and in Meso-America an almost identical calendar system was devised.

However, the Babylonians (and probably the Sumerians before them) took the decimal and 60 unit sexagesimal system one step further and invented a way to write these numbers in a temporal sequence, the grammatical order of which revealed the value of the sum. In this manner, thanks to the Sumerian-Babylonians, when one writes 4254, it is clear that the first "4" is a thousand times greater than the last "4". It was not until the ancient Hindu's appeared on the scene that the concept of "nothing" and thus "zero" came into being.

Just as written language soon came to be organized in a non-pictorial series of temporal sequences, so to did the understanding of the cosmos, geometry, time, and numbers. These tremendous intellectual and creative achievements, however, like language, were dependent on the functional integrity of the inferior parietal lobe (as well as other neural structures such as located within the frontal and temporal lobe and the thalamus), for with the destruction of this tissue, one's sense of time, space, geometry, written language, and math is abolished.

With the advent of language and the ability to analyze events in regard to temporal sequences, not only linguistic usage, but nature and reality itself has in consequence become fragmented. This is a consequence of the development of grammar which requires that all that is formulated within a linguistic framework be sequenced and arranged in a certain order. The continuity and flow of events and actions has become subject to segmentation into distinct things. A tree ceases to be part of the forest where birds and animals roam and live, but a word, distinct, separate and isolated, much in the same manner that most human beings have become separate and psychically isolated from nature and their environment. Reality has come under the yoke of language and the ability to label and sequence, and so too has a good part of the human mind and brain.

Copyright: 1996, 2000, 2010, 2018 - Rhawn Joseph, Ph.D.