Consciousness, the Threshold Between Mind and Matter

“Ours is a world of words: Quiet we call

Silence — which is the merest word of all.” Al Aaraaf by Edgar A. Poe

One of the most characteristic abilities of humans is the ability to produce and understand complex language that is primarily abstract and metaphorical in nature. This stands in stark contrast to the gestures and innate calls of other animals which are reactive in nature, that is to say animals can only communicate about items in their immediate environment while human speech doesn’t rely on environmental triggers.[1, 2] Since the early development of language didn’t leave a distinct archaeological record which can be examined, in order to study its development we must examine physical evidence such as the tools left behind by early man as well as neurological studies, many of which compare the brain of man to that of closely related primates.

Hominins have been using stone tools for at least 2.6 million years, the earliest of these were made by using a hard cobble, known as a hammerstone, to strike off flakes from a softer piece of stone known as a core.[See image below, Figures 1, 2, Video 1] These early stone implements are referred to as Oldowan tools, despite being simple flakes and choppers which were only worked on one surface they were in use for almost one million years. It’s unclear which hominin species initially created these tools, but one thing which is clear is that multiple species ended up using them, including several members of the Homo family including H. australopithecus, H. habilis, H. ergaster, and early Homo erectus.[3] These simple implements were gradually replaced by the more advanced Acheulean tools starting around 1.75 million years ago– an important note here is that the older tools continued to be used, and manufactured, despite the advancement.[4] Acheulean tools, which were predominantly pear-shaped handaxes, were worked symmetrically on both sides so that they could fit in the palm while also having a much larger cutting surface, this level of attention to detail and standard form seems to indicate a great cognitive stride had been made.[See Figures 3, 4, Videos 2, 3] Whereas early stone tools required only a single hammerstone, the production of Acheulean handaxes is a multistage process which required at least two types of hammerstones, a coarse stone for abrasion, and a baton made of antler, bone, or wood, for knocking thin flakes off of the stone.[5, See Figure 5]

Oldowan Chopping Tool

Oldowan Chopping Tool

Acheulean Handaxe

Acheulean Handaxe

When you compare the simple pebble tools of the Oldowan Industry to those of the Acheulean it becomes obvious that these later tools require much greater motor skill, a knowledge of the properties of stone, and also careful planning in order to create an intentionally shaped tool.[5] In a detailed analysis of the Oldowan Industry from a primatologist point of view Wynn and McGrew (1989) came to the conclusion that “all the behaviour that can be inferred from Oldowan tools and sites falls within the range of the ape adaptive grade. There is nothing exclusively human-like about this oldest known archaeological evidence.”[6] The authors of the study made this assessment based primarily upon how early stone tools could be manufactured using simple spatial concepts, they aren’t symmetrical, and could be created by repeatedly striking a hammerstone against a core/cobble within close proximity– living apes follow similar procedures to create various tools which they employ. In contrast, Acheulean tools were worked symmetrically on both sides, and many of these tools incorporate hand/finger grips, rounded ends to distribute shock over the entire palm, and even centrally located fossils which may indicate aesthetic concern.[See examples 7, 8, 9, 10, 11, 12]

From knapping to language to the conscious mind

Historical Development of Toolmaking Industries, and Jaynes’ Proposed Timeline of the Development of Speech

Many anthropologists consider the use of symbols to be an essential if not defining aspect of culture, which has been defined by the founder of cultural anthropology Edward B. Tylor as “that complex whole which includes knowledge, belief, art, morals, law, custom, and any other capabilities and habits acquired by man as a member of society.”[13] Anthropologist Ralph L. Holloway, Jr. stated that the definition of culture should also include the “imposition of arbitrary form upon the environment” as “these two attributes are specific and unique to human behavior, and they can be identified by the appearance of stone tools in the archaeological record.”[14] An important characteristic of the tools of early man is their non-iconic nature (indicated by the term arbitrary form), when you compare these early tools to those of animals you see that even the tools of primates are iconic, as in a stick used for fishing for termites is still a stick despite having the leaves removed from it. In contrast, the standardized form of Acheulean tools indicates that there are systematic rules which one must follow in order to transform a stone into a handaxe– Holloway points out that these chained actions are a type of grammar consisting of a “basic “vocabulary” of motor operations– flake detachment, rotation, preparation of striking platform, etc.” Holloway describes the grammar of tool-making in greater detail in the following section:

Returning to matters of syntax, rules, and concatenated [chained] activity mentioned above, almost any model which describes a language process can also be used to describe tool-making. This is hardly surprising. Both activities are concatenated, both have rigid rules about the serialization of unit activities (the grammar, syntax), both are hierarchical systems of activity (as is any motor activity), and both produce arbitrary configurations which thence become part of the environment, either temporarily or permanently.

An important component of culture is the feedback cycle created by the tools, or arbitrarily structured environment, as the “altered environment shapes (man’s) perceptions, and these are again forced back upon the environment, are incorporated into the environment, and press for further adaptation.” So early man shapes a rock into a tool and in the process of doing so he shapes his own brain (neural networks, etc) and then once the tool is used it changes how man interacts with the environment which then gives feedback as to its efficiency.

Over the last few decades several interesting studies have examined the functional difference in Oldowan versus Acheulean tool-making as well as the importance of stone knapping toward the development of early language, these studies have shone light on the dark recesses of the Early Stone Age (ESA). One particular study used a type of neuroimaging, fTCD, which measures changes in cerebral blood flow to determine which areas of the brain were activated while completing one of two tasks, creating an Acheulean handaxe or a language task.[15] The findings of the study are summed up in the following section:

Making an Acheulean handaxe requires both working memory and planning memory. This careful planning is dominant in the initial phase of each experimental block in our study. This action planning draws on brain areas that are shared with language tasks, such as the left-lateralized ventral premotor areas and Broca’s area. Our subject pool shows highly correlated individual brain blood flow lateralization in the early phases of task execution for both tasks. Our findings add empirical data to the hypothesis that action planning for tool-making and language draw on shared functional brain structures. The correlated time-signatures for Acheulean knapping and language, which remain significantly correlated within subjects despite variability between subjects, indicates that the same brain networks are being activated for both tasks. They suggest that tool-making and language share a basis in more general human capacities for complex, goal-directed action.

This study demonstrates that language and tool-making share the same neural pathways, perhaps this is because of the countless generations of hominids activating these networks with the orderly, precise techniques required for Acheulean tool-making– as Princeton psychologist Julian Jaynes said “There is nothing in consciousness [introspectable mind-space] that is not an analog of something that was in behavior first” and likewise, there is no symbolic language without its physical precedent, syntax. [See schematic diagram for “Brain regions activated during speech and action observation, tool-use, word generation, and Acheulean knapping”]

Another interesting study used a different type of neuroimaging, PET, which produces real-time three-dimensional images of the brain to map out the areas which are being used by an activity, in this case it was either Oldowan or Acheulean toolmaking by expert subjects.[5] The subjects were all “professional archaeologists with more than 10 years stone toolmaking experience and already familiar with Oldowan and Late Acheulean technologies,” their tasks (which were divided over three days) were to create Oldowan-style tools, Acheulean handaxes, and a control task in which they were instructed to strike cobbles together without using any specific toolmaking techniques. Upon reviewing the results, the researchers noted that, “As expected, expertise was associated with increased IPL [Inferior Parietal Lobule] activation during Oldowan toolmaking. However, contrary to expectation, this activation was strongly bilateral.” They went on to say that it appears that improved handaxe creation is a result of more accurate neural representations of the body-tool combination, and not a consequence of enhanced motor planning/strategy as they had expected. The enhanced sensorimotor representations of the tool-body system could perhaps have been developed through the millennia as hominids worked with stone tools, leading to what is essentially a more accurate neural analog of the body.

Language Areas of the Brain

Language Areas of the Brain

The primary area of the brain related to tool usage is the Inferior Parietal Lobule, the left IPL is located at the meeting place of the auditory, visual, and somatosensory (touch, temperature, pain, and limb position) cortexes and it is deeply connected with all of these structures. Because of these connections, the IPL is one of the primary areas for processing auditory and visual information and it is particularly important to language comprehension and mathematics– as well as memory retrieval, attention, and theory of mind.[16] The right IPL, on the other hand, “organizes many spatial functions for both sides of the body and for both sides of external space.”[17] The IPL is divided into two parts, the Supramarginal Gyrus and the Angular Gyrus, the AG is associated with complex language functions like reading, writing, and interpreting the meaning of writing; pioneering neurologist Norman Geschwind hypothesized that this area was responsible for translating written word to internal monologue. The right AG is responsible for spatiovisual attention as well as maintaining an awareness of the self through monitoring intended actions and the resulting actual movement, the discrepancy between these two allows the AG to maintain an awareness of the self.[18] While not as involved as the AG, the Supramarginal Gyrus, or SMG, assists in language perception and processing, as well as being a part of the previously mentioned somatosensory cortex of which the SMG is particularly important in the perception of space and the location of limbs. The SMG is also a part of the mirror neuron system which is made up of neurons which are activated when an animal performs a specific action or observes another performing the same action. A recent study conducted using fMRI found that both humans and monkeys have activity in corresponding regions of the brain when observing hand actions and actions performed using simple tools, but in the humans there was additional activity in an area at the front of the left SMG (the left aSMG) while viewing actions performed using tools.[19] The authors of the study stated that the activity in the left aSMG was only present when observing “goal-directed action performed with a mechanical device, vanishing when the goal of the action was omitted from the videos,” this led them to believe that the area had evolved specifically for tool use.

Although both hemispheres are used for language to some degree, in the majority of people (approximately 97%[20]) the left hemisphere is the one where most linguistic processing takes place while the right hemisphere deals with minor functions like intonation/accentuation, prosody, pragmatic, and contextual aspects of language.[21] The areas of the brain involved in language are more numerous than once thought, but the three major areas are Broca’s Area, Wernicke’s Area, and the Inferior Parietal Lobule. A fascinating feature of the cerebral hemispheres is pointed out by neurologist Joseph LeDoux in the following quote:

The primary functional distinction between the human hemispheres thus involves the differential representation of linguistic and spatial mechanisms: These mechanisms, moreover, are selectively represented in restricted zones within each half-brain. It is of particular interest to note that while the IPL in the left hemisphere is involved in linguistic processing (see above), the right IPL is involved in spatial processing. Thus, the two functions that comprise the primary functional axis of brain asymmetry are dependent, in part, upon the integrity of homologous areas in opposite hemispheres. This complementary organization of IPL in the two hemispheres is, I believe, an important clue to the origin of human brain asymmetry.

The story begins to unfold when we consider several factors discussed earlier: Spatial mechanisms are represented in both the left and right IPL in nonhuman primates and these mechanisms are similar in many respects to the spatial functions of the human right IPL. Given that the nonhuman primate IPL and the IPL in man’s minor hemisphere are homologous brain structures related through common ancestry (see LeDoux, 1982, for discussion) an important insight emerges: In man, language is represented in a region (IPL) of the major [dominant] hemisphere which, in the minor hemisphere, is involved in spatial functions, and was involved in spatial functions in both hemispheres of man’s ancestors.[For background info on the terms major and minor hemisphere see Note 1] The unavoidable conclusion of this line of reasoning is that the evolution of language involved adaptations in the neural substrate of spatial behavior.[17]

This quote has particular importance to a theory of the origin of human consciousness called the Bicameral Theory of Mind, the creator of this theory, Princeton Psychologist Julian Jaynes theorized that thousands of years ago the human mind was divided into two chambers.[If you’re not familiar with the Bicameral Theory of Mind please read the short summary here: ] One of these chambers was used for basic functions which the individual had either been taught by their culture (like hunting, making shelters, etc) or learned and repeated many times while the other area was only used in the rare circumstance that a person encountered a completely novel, dangerous situation. This type of person was said to be bicameral, they lacked the ability to introspect or reason with logic so when they encountered a situation like a bear suddenly emerging from a cave nearby the other chamber of their mind would use past experience and tell the man side of the mind what to do– this was experienced as an auditory hallucination, and if this seems hard to believe then one needs only to look at the number of people today who experience hallucinations when under severe stress or isolation. When reviewing the studies which were cited previously with this theory in mind an interesting picture begins to develop, but before surveying this we should turn to a paper which was referenced by the PET study of Oldowan and Acheulean toolmaking. In a paper titled Functional Precursors to Language and its Lateralization the authors describe how language has a “frame-content mode of organization: at the phonological level, consonant and vowel elements are inserted into syllabic frames; and at the morphological level, stem forms of content words are inserted into syntactic frames.”[22, See image below] The authors of the paper then go on to propose that lateralization of brain function developed first for bimanual coordination, as is seen with stone toolmaking, before being used for language. Returning to the task at hand, the previously mentioned PET study stated that the function of the non-dominant hand is “not simply to execute gestures more typically done with the dominant hand but rather to properly position and support the core to receive the action of the dominant hand.”[5] In other words, the content, or dominant hand, acts upon aspects of the environment which are framed, or held carefully in place, by the non-dominant hand; in this context, what is described here is what could be referred to as the Frame-Content Phenomenon where the dominant hand, which is usually the right one, would act upon the environment in a very direct way while the non-dominant hand would react to the actions of the dominant hand and the subsequent change cascade caused in the environment (mathematically that would be: the actions of the Right Hand + the change/resistance induced in the Environment + Past Learning + spatial detection = Left Hand reaction/movement). This has a specific significance to the Bicameral Theory of Mind, as the dominant hand would essentially be the hand of man while the non-dominant would be the hand of god; Jaynes described the hallucinatory god voice as being made up of “stored-up admonitory wisdom,” and this past learning would be a part of my proposed formula, but there are other factors as well– all of which are characterized by the visual aspect of the right hemisphere, like current visuospatial processing and encoded visual memories which rely on a steady mental frame, aspects of which were learned, while other features were inborn.

From Frame to Content, from Matter to Mind

Frame-Content Theory of Language

The IPL contains what are referred to as multimodal neurons, these neurons are capable of processing various senses simultaneously instead of being specialized for a single function like most neurons. This would seem to be essential for their proper function as the left IPL is located at the meeting place of the auditory, visual, and somatosensory cortexes where it acts as a bridge for the integration of the various senses.[16] Renowned neurologist V.S. Ramachandran has written about how he considers a portion of the IPL, the Angular Gyrus, to be critical to the understanding of metaphors because of its multimodal nature and position at the juncture of the various cortexes[23]. Some linguists consider language to be built from metaphor as there would be a limited number of possible utterances if an individual were to only use words in their most literal sense, but metaphor carries meaning from one object to another because of some similarity between the two. Many metaphors are cross-modal, as in a sharp cheese, loud shirt, or bitter cold, the reason for this would seem to be because we label the unknown in the terms of the known– this labeling would seem to be an essential quality of subjectivity, and interestingly the Angular Gyrus has been shown to “be directly involved when you assign a name to an object or when you read its name.”[16] According to the Bicameral Theory of Mind, metaphor was essential to the development of consciousness, which Jaynes defined as “that which is introspectable,” or “an analog ‘I’ narratizing in a functional mind-space.” What exactly is a functional mind-space, and what does metaphor have to do with it? Since a metaphor transfers the usage of one term, or phrase, to describe something else because of a perceived similarity of the two things, or because of a certain relationship which the objects share, it allows one to distill the essence of something so that it can be easily communicated to someone else– in a similar way metaphor could allow for the easier mental manipulation of what would otherwise be too complex to process, or store in short-term memory. [For an in-depth discussion of the importance of metaphor toward consciousness see my previous post:]

A 2010 meta-analysis of the literature on laterality of motor control by Charleston neurologist Iraj Derakhshan came to a surprising conclusion, that Newton’s theory of the laterality of the brain is incorrect. In short, Newton’s theory is that “each hemisphere controls movements of the other side of the body and that the sensations arising from each side achieve consciousness in the opposite hemisphere; i.e. that there are two “endpoints in visuomotor stream,” one for each side of the body”[24] This theory has been accepted for over 300 years as a result of its simplicity, and also because Newton had such a profound influence on physics and mathematics. By providing numerous pieces of evidence after carefully reviewing clinical and experimental literature Dr. Derakhshan demonstrated that

“brainedness (i.e. the laterality of the executive hemisphere) stands for the destination of all signals achieving consciousness and that the minor hemisphere represents three-dimensional reality of space. Awareness to that reality, however, awaits arrival of signals arising from the nondominant side of the body/space to the major hemisphere via the posterior aspect of the callosum.”

The studies presented previously demonstrate that the right hemisphere is specialized for visuospatial processing, and is similar in many ways to that of both hemispheres of the nonhuman primate, while the left hemisphere is specialized for linguistic processing, syntax, and time, so it would be safe to say that at one time both hemispheres of man were utilized for visuospatial processing and that as language developed it began to build upon the previous functions/structure of the left hemisphere. As this process was happening, likely over a span of hundreds of thousands of years and numerous different species of hominids, the left hemisphere became the place where reality was distilled/subjectified, in the sense that a map, for example, relies on spatial coordinates where the distance between two points is objective (though some maps are more accurate than others, they are still created to represent a specific terrain which should be very similar from case to case) while a novel object, situation, art, etc is always dependent on past experiences and language. Thus we see that the fundamental function of the right hemisphere is to “represent three-dimensional reality of space,” while the role of the left hemisphere is to learn, and process, language which allows for an awareness that can then be used to subjectively pilot the machine.

Derakhshan’s One-way Callosal Traffic Theory has profound implications for Jaynes’ Bicameral Theory of Mind, but before elaborating on this I would like to draw your attention to the following quote from Jaynes:

Subjective conscious mind is an analog of what is called the real world. It is built up with a vocabulary or lexical field whose terms are all metaphors or analogs of behavior in the physical world. Its reality is of the same order as mathematics. It allows us to shortcut behavioral processes and arrive at more adequate decisions. Like mathematics, it is an operator rather than a thing or repository. And it is intimately bound up with volition and decision.(pg 55)[2]

Analog and metaphor are important parts of Jaynes’ theory, notice that these two functions are made possible by spatial and linguistic mechanisms respectively, once again this demonstrates the tendency of evolution to rebuild upon an already successful model, in this case the frame-content mode of organization. As spatial mechanisms are represented in the right hemisphere, and linguistic processing in the left, it would seem that the right hemisphere would construct a visuospatial analog of the world and the left hemisphere would act upon it with metaphor– just as ancient man struck stone cobbles together to create tools, post-linguistic man manipulates metaphors in mind-space so that he could not only construct possible futures, but examine the recreated past. Before early man acquired metaphor it would appear that he could not move through mind-space in this way, so he lacked introspection, reason, and the ability to examine the past, or consciously project possible futures, but it’s likely that experience was still constantly being taken in by the visuospatial networks of the mind which would calculate the best possible action/movement in a given situation and project this to the left hemisphere in times of need. When viewing the Bicameral Theory of Mind in relation to the One-way Callosal Traffic Theory one quickly notices that in both theories the same side of the brain is responsible for motor signals, these are referred to as the man side of the brain and the major hemisphere respectively, this is essentially the intermediary of the individual and the environment. The god side of the brain and the minor hemisphere are more of an intermediary between the individual and the past, and visuospatial calculation, neither of these aspects require language as they would rely on visuospatial processing to reconstruct visually encoded memories and/or calculate movement.

The picture which is beginning to develop is that for hundreds of thousands of years early hominids created some of their first tools primarily with their right hand, and subsequently left hemisphere, this specialized the motor cortex and other circuits to process syntax. After producing these tools for close to a million years a more advanced type of stonework took shape, this industry, the Acheulean, required much more precision and visuospatial processing skill, this enhanced the right hemisphere’s ability to “frame situations” or focus on what action would be the most likely to be successful, at least mathematically speaking. In a sense, the right hemisphere retained the animal/visuospatial mind as the left hemisphere became more and more accustomed to syntax, time, and subsequently language, thus we get the dualism inherent in the mind of man, where man is constantly in opposition to his animalistic nature. After millennia of framing situations so that man knew where to appropriately inject content he had reached a point where the non-conscious animal mind could be used as a divine source of guidance in times of need: a silent sentry that calculated not just the best possible movement for the left hand under certain conditions, but also the best possible course of action for the bicameral man in a dangerous situation by utilizing Wernicke’s Area (the right hemisphere area responsible for speech production) so that the individual would hear a command telling him what to do. As the conscious mind developed this focus was less strictly limited to specific situations, and manifested as inspiration from past events, both remembered and unremembered, and it could be occasioned by the use of certain drugs, meditation, stress, or other altered states of consciousness. There’s something indescribably beautiful about the left hand being both the hand of god, and of the animal mind, and I have no doubt that this is a large part of why so many ancient, and modern, cultures are biased against the left hand/side– the personal god, and man’s animal nature, stands in contrast to that of holy doctrine. [For more on the negative connotation of left-handedness, see Wikipedia: Bias Against Left-handed People]

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References Section
[1] Jane Goodall, who is considered by many to be the leading expert on chimpanzees (which are the closest living relative of humans), has studied primates extensively over half a century and had this to say about the usage of language by chimps: “What’s the one obvious thing we humans do that [chimps] don’t do? Chimps can learn sign language, but in the wild, so far as we know, they are unable to communicate about things that aren’t present. They can’t teach what happened 100 years ago, except by showing fear in certain places. They certainly can’t plan for five years ahead. If they could, they could communicate with each other about what compels them to indulge in their dramatic displays. To me, it is a sense of wonder and awe that we share with them. When we had those feelings, and evolved the ability to talk about them, we were able to create the early religions.”
[2] Deacon, T.W. (1997) The Symbolic Species: The Co-evolution of Language and the Brain. New York: W.W. Norton & Company, Inc.
[3] Richards, M. (2002). A Brief Review of the Archaeological Evidence for Palaeolithic and Neolithic Subsistence. European Journal of Clinical Nutrition, 56(12), 1270-1278. Retrieved March 3, 2015, from
[4] Beyene, Y., Katoh, S., Woldegabriel, G., Hart, W., Uto, K., Sudo, M., … Asfaw, B. (2013). The Characteristics and Chronology of the Earliest Acheulean at Konso, Ethiopia. Proceedings of the National Academy of Sciences, 110(5), 1584-1591. Retrieved March 7, 2015, from
[5] Stout, D., Toth, N., Schick, K., & Chaminade, T. (2008). Neural Correlates Of Early Stone Age Toolmaking: Technology, Language And Cognition In Human Evolution. Philosophical Transactions of the Royal Society B: Biological Sciences, 363(1499), 1939-1949. Retrieved March 10, 2015, from
[6] Wynn, T., & McGrew, W. (1989). An Ape’s View of the Oldowan. Man. Published by: Royal Anthropological Institute of Great Britain and Ireland, 24(3), 383-398. Retrieved March 18, 2015, from
[7]World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[8] World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[9] World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[10] World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[11] World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[12] World Museum of Man. (n.d.). Retrieved March 8, 2015, from
[13] Tylor, E.B. (1881). Anthropology an Introduction to the Study of Man and Civilization. London: Macmillan and Co.
[14] Holloway Jr., R. L. (1969). Culture: A Human Domain. Current Anthropology. 10(4). Retrieved March 10, 2015, from,+Jr.,+Culture.+A+Human+Domain.pdf
[15] Uomini, N., Meyer, G., & Petraglia, M. (2013). Shared Brain Lateralization Patterns in Language and Acheulean Stone Tool Production: A Functional Transcranial Doppler Ultrasound Study. PLoS ONE, 8(8), E72693. Retrieved April 14, 2015, from
[16] Dubuc, B. (2002). The Brain from Top to Bottom. Broca’s Area, Wernicke’s Area, and Other Language-Processing Areas in the Brain. Retrieved April 21, 2015, from
[17] LeDoux, J. (1984). Cognitive Evolution: Clues from Brain Asymmetry. The Right Hemisphere: Neurology and Neuropsychology (A. Ardila & P. Ostosky-Solis, Eds.), Vol. 1, 51-60. New York: Gordon and Breach. Retrieved April 21, 2015, from
[18] Farrer, C., Frey, S., Horn, J., Tunik, E., Turk, D., Inati, S., & Grafton, S. (2007). The Angular Gyrus Computes Action Awareness Representations. Cerebral Cortex, 18(2), 254-261. Retrieved May 24, 2015 from
[19] Peeters, R., Simone, L., Nelissen, K., Fabbri-Destro, M., Vanduffel, W., Rizzolatti, G., & Orban, G. (2009). The Representation of Tool Use in Humans and Monkeys: Common and Uniquely Human Features. Journal of Neuroscience, 29(37), 11523-11539. Retrieved May 31, 2015.
[20] Fitzpatrick, D. (2004). Language and Lateralization (D. Purves, G. Augustine, & D. Fitzpatrick, Eds.). Neuroscience. Sunderland, Mass: Sinauer Associates
[21] Seghier, M. (2012). The Angular Gyrus: Multiple Functions and Multiple Subdivisions. The Neuroscientist, 19(1), 43-61. Retrieved May 24, 2015, from
[22] MacNeilage P.F, Studdert-Kennedy M.G, Lindblom B. (1984). Functional Precursors to Language and its Lateralization. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, 246(6), R912-R914. Retrieved June 7, 2015, from
[23] Ramachandran, V.S., Hubbard, E.M. (2003). The Phenomenology of Synaesthesia. Journal of Consciousness Studies, 10(8), 49-57. Retrieved May 4, 2015, from
[24] Derakshan, I. (2010). It Is All Quiet in the Minor Hemisphere: A Fresh Look into the Laterality of Consciousness, Vision and Attention in Human Brain. Biomedicine International Journal, 1(1). Retrieved June 7, 2015, from

[Note 1] The terms major and minor hemisphere are used by many specialists to denote that one hemisphere doesn’t dominate the other, or that one hand is not more important than the other simply because it is more dexterous. Both hands are specialized to act in conjunction where each hand is essentially a motor and by using them together they work in a series.

Metaphor and the Mind

The drive toward the formation of metaphors is the fundamental human drive, which one cannot for a single instant dispense with in thought, for one would thereby dispense with man himself.
— Friedrich Nietzsche

Metaphor is the often overlooked and undervalued engine which provides much of the power of language, and it allows for the exponential expansion of our otherwise concrete system of symbols. The word metaphor comes from the Greek word metaphora, meaning “a transfer,” particularly in “the sense of one word to a different word, literally “a carrying over.”[1] Like it’s name suggests, a metaphor transfers the usage of one term, or phrase, to describe something else because of a perceived similarity of the two things, or because of a certain relationship which the objects share.

We see the world through the lens of language, the perception of new objects which we encounter is based upon our existing vocabulary– as Julian Jaynes states in The Origin of Consciousness in the Breakdown of the Bicameral Mind, “language is an organ of perception, not simply a means of communication.”(pg 50)[2] When books were first made available many years ago a person who encountered one may have been perplexed by it, they may have seen someone looking at words on a page and thought “a box made out of tablets.” Then when they saw how easily the person flipped to the next page they may have thought, “it’s a tree made out of leaves of words!” Interestingly enough, the word book comes from the Proto-Germanic word meaning “beech … the notion being of beechwood tablets on which runes were inscribed, but it may be from the tree itself.” [3] Many of the metaphors we use today are considered dead metaphors, meaning that they were used so often that the imagery associated with them is essentially lost (a good example of this would be “iron resolution”)– oftentimes this occurred so long ago that most people don’t even realize that imagery was once connected to it. This quote from Jaynes provides two excellent examples of words which were at one time metaphors:

Even such an unmetaphorical-sounding word as the verb ‘to be’ was generated from a metaphor. It comes from the Sanskrit bhu, “to grow, or make grow,” while the English forms ‘am’ and ‘is’ have evolved from the same root as the Sanskrit asmi, “to breathe.” It is something of a lovely surprise that the irregular conjugation of our most nondescript verb is thus a record of a time when man had no independent word for ‘existence’ and could only say that something ‘grows’ or that it “breathes.” Of course we are not conscious that the concept of being is thus generated from a metaphor about growing and breathing. Abstract words are ancient coins whose concrete images in the busy give-and-take of talk have worn away with use.(pg 51)[2]

At the most basic level, how exactly does metaphor operate? A metaphor is made up of two parts, the metaphier and the metaphrand*– the metaphrand is the unknown/unlabeled object which needs illumination, and the metaphier is the familiar source which provides this.[See Figure 1] In a sense, the metaphier is an iron statue in the mind, while the metaphrand is an unknown ore, in order to try to try to understand what the metaphrand is it must be melted down by the senses into it’s constituent forms which can then be poured into the mold of an existing statue. Anytime you melt down ore there will always be slag, or glass-like byproducts which are discarded, but this is the nature of perception– something is always lost when a thing changes from one form to another. A similar reaction occurs when a person attempts to hand an iron statue to another, the entire statue can’t be handed over, so instead the parts of the statue are described in a way that leads the other person to craft a similar sculpture in their own mind. With art, especially visual art, the artist is able to put down on paper (or whatever medium) what otherwise would be a fleeting idea or image and in doing so others may get a glimpse of the mysterious workings of another’s mind.

Figure 1: Metaphor Map- As Above, So Below

Figure 1: Metaphor Map – As Above, So Below


Analogs are also an important part of cognition, they are a type of model which is generated directly from it’s source on a point by point basis as is the case with a map. Jaynes describes maps, and analogs, in this way:

It [a map] is not a model in the scientific sense, not a hypothetical model like the Bohr atom to explain something unknown. Instead, it is constructed from something well known, if not completely known. Each region of a district of land is allotted a corresponding region on the map, though the materials of land and map are absolutely different and a large proportion of the features of the land have to be left out. And the relation between an analog map and its land is a metaphor.(pg 54)[2]

Analogs allow us to share, and preserve, knowledge in a visual way so that it’s easy to understand, in a sense they could be considered a universal language. Like metaphors, analogs simplify something which would otherwise be too complex to understand or communicate.

Now that it’s clear how metaphor allows a limited number of symbols to transfer over to an unlimited amount of situations, and that analogs are a simplified visual representation of something too complex to understand or communicate, then hopefully this next quote from Jaynes wont seem too implausible:

Subjective conscious mind is an analog of what is called the real world. It is built up with a vocabulary or lexical field whose terms are all metaphors or analogs of behavior in the physical world. Its reality is of the same order as mathematics. It allows us to shortcut behavioral processes and arrive at more adequate decisions. Like mathematics, it is an operator rather than a thing or repository. And it is intimately bound up with volition and decision.(pg 55)[2]

Metaphor is essentially the building blocks of the mind, and analog is the place where architecture occurs. By manipulating these building blocks into countless different positions and patterns we’re able to quickly think out what would happen if we were to commit to any particular action thus we are able to project possible future outcomes before deciding which one would be the most beneficial. An important, related part of consciousness is what Jaynes referred to as the “analog I,” this is essentially the metaphor that we have of ourselves– Jaynes describes this mental feature in the following section:

[Consciousness] operates by way of analogy, by way of constructing an analog space with an analog ‘I’ that can observe that space, and move metaphorically in it. It operates on any reactivity, excerpts relevant aspects, narratizes and conciliates them together in a metaphorical space where such meanings can be manipulated like things in space. Conscious mind is a spatial analog of the world and mental acts are analogs of bodily acts. Consciousness operates only on objectively observable things. Or, to say it another way with echoes of John Locke, there is nothing in consciousness that is not an analog of something that was in behavior first. (pg 65-66)[2]

In a universe which is infinitely large metaphor is a net which allows us to catch otherwise fleeting details and label them so that they can be perceived, spoken about, and recalled. It is this process of labeling that allows us to simplify and then examine the world around us; the forms/particulars which we see are concrete/solid, so they must be distilled before they can fully enter our conscious mind.[See Figure 2] Since we see the world through the lens of language, and metaphor allows for the infinite expansion of our limited set of symbols, it goes to follow that metaphor allows for the expansion of our mind in a similar way. As cognition, and perception, are based on language there would be a natural limit on them if not for the expansive power of metaphor which carries meaning from one subject to another.

Ether-Ore: Metaphor, Particular, Perception

Figure 2: Ether-Ore – Metaphor, Particular, Perception

We believe that we know something about the things themselves when we speak of trees, colors, snow, and flowers; and yet we possess nothing but metaphors for things– metaphors which correspond in no way to the original entities.
— Friedrich Nietzsche

* These are the two parts of a metaphor with the words coined by Jaynes (the terms were based on multiplication wherein a multiplier operates on a multiplicand), there are other similar terms which were created by other writers but they had a slightly different connotation– the most commonly used terms today seem to be “tenor” and “vehicle” which were created by I. A. Richards.

[1] Online Etymology Dictionary, metaphor:
[2] Jaynes, J. (1976). The Origin of Consciousness in the Breakdown of the Bicameral Mind. Boston: Houghton Mifflin.
[3] Online Etymology Dictionary, book:

Doubt, the Catalyst for Consciousness

Dubito, ergo cogito, ergo sum

“I doubt, therefore I think, therefore I am” is one of the most simple, but significant philosophical statements of all time. Hidden within that simplicity is the foundation for all knowledge. Only by doubting can one be certain of one’s own existence, because the process of doubting requires a subject capable of introspection. As Dr. Julian Jaynes said in The Origin of Consciousness in the Breakdown of the Bicameral Mind, “The eye cannot doubt or be in conflict, as the soon-to-be-invented conscious mind will be able to.” (pg 70)[1]

Before modern consciousness existed, while man was transitioning from a bicameral (‘two-chambered’) state of mind, he didn’t have the ability to introspect, reflect on the past, or imagine any possible future– he was controlled by his environment, acting in a stimulus-response manner (if you’re not familiar with the Bicameral Theory of Mind please read the short summary here: During this time period, there were what Dr. Jaynes referred to as the preconscious hypostases, these were physiological responses which instigated behavior, as in the way someone’s breathing might increase as an enemy force charges onto a battlefield and this leads them to fight or flee. In the Iliad, these respiratory changes were referred to as phrenes, and they could cause a cascade of physical reactions in the body that would lead a person to commit to a certain action. Or, as Jaynes says, “The preconscious hypostases are the assumed causes of action when other causes are no longer apparent. In any novel situation, when there are no gods, it is not a man who acts, but one of the preconscious hypostases [bodily sensations] which causes him to act. They are thus seats of reaction and responsibility which occur in the transition from the bicameral mind to subjective consciousness.” (pg 259)[1]

Although not a physiological response, doubt, likely caused by an interruption in a signal being sent from one area of the brain to another, could be one of the most powerful internal sensations which Dr. Jaynes referred to as the preconcious hypostases. When a message is sent from one area of the brain to another, but it never arrives because of a signaling issue there is a feeling of doubt which is not easy to overcome– it makes one question whatever has entered their mind. If someone is able to question what they see, hear, or feel, then that displays more than a simple sense, it demonstrates that their senses are being interpreted. In this way, neurological doubt, as opposed to Descartes’ hyperbolical/metaphysical doubt, may have preceded consciousness, and in fact be the primary cause of consciousness as we know it. It’s important to state here that I use the definition of consciousness which was put forth by Dr. Julian Jaynes, and Descartes, in its simplest terms it would be “that which is introspectable.”

If Jaynes is correct, and consciousness emerged in the Middle East sometime around 1000 B.C. then the literature from that time period should reflect this, and indeed it does. While examining the Old Testament, Dr. Jaynes stated that “it is possible to look upon it [the Fall of Man] as a myth of the breakdown of the bicameral mind. The Hebrew arum, meaning crafty or deceitful, surely a conscious subjective word, is only used three or four times throughout the entire Old Testament. It is here used to describe the source of the temptation. The ability to deceive, we remember, is one of the hallmarks of consciousness. The serpent promises that “you shall be like the elohim [Gods] themselves, knowing good and evil” (Genesis 3:5), qualities that only subjective conscious man is capable of. And when these first humans had eaten of the tree of knowledge, suddenly “the eyes of them both were opened,” their analog eyes in their metaphored mind-space, “and they knew that they were naked” (Genesis 3:7), or had autoscopic visions and were narratizing, seeing themselves as others see them. And so is their sorrow “greatly multiplied” (Genesis 3:16) and they are cast out from the garden where He-who-is could be seen and talked with like another man.” (pg 299)[1]

I believe that within the Biblical tale of the fall of man lies the biological cause of increased doubt, which led to subjectivity– the Forbidden Fruit. Many scholars think that the fruit of the Tree of the Knowledge of Good and Evil is merely a metaphor, but this doesn’t mean that there wasn’t a biological basis for it. In the Garden of Eden God commanded Adam, “You are free to eat from any tree in the garden; but you must not eat from the tree of the knowledge of good and evil, for when you eat from it you will certainly die.” (Genesis 2:16-17), but why would this be? It seems apparent to me that the myth details not just the acquisition of consciousness, but also of man’s change from a hunter-gatherer lifestyle to an agrarian one. This is most evident in Genesis 3:17-19:

17 To Adam he said, “Because you listened to your wife and ate fruit from the tree about which I commanded you, ‘You must not eat from it,’

“Cursed is the ground because of you;
through painful toil you will eat food from it
all the days of your life.
18 It will produce thorns and thistles for you,
and you will eat the plants of the field.
19 By the sweat of your brow
you will eat your food
until you return to the ground,
since from it you were taken;
for dust you are
and to dust you will return.”

In the narrative, Adam, which is derived from the Hebrew word for soil (adama) as he was created from the earth, was exiled from the garden where he was forced to work the fields in order to eat for the remainder of his life. The name Chava (Eve’s name in the original text) is derived from the Hebrew root chayah meaning life– this is very interesting because she is the first being made from another living creature as all other organisms before her had been formed out of the ground. As you can see, the writers of the Old Testament were very careful with their words, so it’s no coincidence that the Hebrew name of the forbidden fruit is a pun on sin; khet is the Hebrew word for sin, and some Rabbinic traditions regard khitah, or wheat, to be a pun on sin. Thus, the story of the Fall of Man explains not just the acquisition of consciousness, but also of man’s change to an agrarian lifestyle because both events were precipitated by the ingestion of wheat.

What did Ancient Hebrew sources say the forbidden fruit was? Rabbi Yehuda/Judah, a 2nd Century wise man who is the most frequently mentioned sage in the Mishnah, the first written compendium of Judaism’s Oral Law, proposed that the fruit was wheat because “a babe does not know to call its mother and father until it tastes the taste of grain.”[2] The first book of the Kabbalah, the Sefer Yetzirah (the Book of Formation) which was said to be written by the patriarch Abraham, says that the forbidden fruit was wheat,[3] this teaching is also found in the Talmud, a collection of the opinions of thousands of rabbis on an assortment of subjects which is second only to the Torah. Many people would question how wheat could be considered a fruit, or a tree; the Talmud says that wheat is a fruit because of the way in which it grows.[4] Sages in the Midrash, an early commentary on Biblical texts, said that wheat once grew as tall as a palm tree, but its height was reduced after mankind had sinned.[5]

While viewing the Garden of Eden myth as a metaphor for the change in ancient man’s way of life, this brings us to the question of why ancient man was not “supposed” to eat wheat. I believe that the simplest, and most logical explanation would be that man has evolved over hundreds of thousands of years to eat vegetation in its natural form; wheat, and most other cereal grains (grass seeds), require mechanical processing and baking before consumption so this is something which man didn’t eat until the point when civilization had advanced to a sufficient degree several thousand years ago in the Levant and Iraq. But, on a physiological level, why was wheat so different from the foods which man was adapted to? Before anatomically modern humans (from approximately 30,000 years ago) began adopting agriculture, their diet consisted of meat, fruits, nuts, legumes, roots and tubers, consumption of cereal seeds hadn’t begun to increase until the end of the Pleistocene around 10,000 years ago. (Constantini 1989)[6] Around this time-period, according to Loren Cordain, “hunter-gatherers occasionally consumed cereal grains; however these foods were apparently not major dietary components for most of the year.”(1999)[7, 8] As the climate in much of the world was becoming more hospitable for humans, large game became more and more depleted, and new sources of food were required for humankind’s ever-increasing numbers– it was at this time that gathered plants were becoming more and more important for survival. Despite their nutritional shortcomings cereal grains have several advantages related primarily to ease of storage and planting, but the major change which grains allowed for was a much greater population density.

Babylon System, Tower of Babel, Tikulti Ninurta: Consciousness

The Tower of Babel by Pieter Bruegel the Elder

The development of large, agricultural societies allowed for the specialization of labor since only a relatively small portion of the population would be required to farm this would leave time for the others to focus on a particular trade like tool-making, cloth-making, and building. This new way of life led not only to social stratification, but also to the exchange of ideas, and the development of organized governments to properly plan and manage surpluses. Looking back, it’s interesting to note that

the extent to which early groups became civilized correlates with the type of agriculture they practiced. That is, major civilizations (in south-west Asia, Europe, India, and east and parts of South-East Asia; central and parts of north and south America; Egypt, Ethiopia and parts of tropical and west Africa) stemmed from groups which practiced cereal, particularly wheat, agriculture (Bender 1975, Adams 1987, Thatcher 1987). (The rarer nomadic civilizations were based on dairy farming.) (Greg Wadley and Angus Martin 2000)[9, 10, 11, 12]

Wadley and Martin go on to offer a possible explanation for this fact– over the last several decades numerous groups of researchers have conducted studies which have demonstrated that cereal seeds, including wheat, maize, and barley, (as well as bovine and human milk), have opioid activity (interestingly enough, wheat and milk also contain proteins which have some degree of stimulatory activity, and also an analog of a dopaminergic peptide called MIF-1).[13, 14, 15, 16, 17] The psychoactive peptides which have been isolated from these seeds are called exorphins “because of their exogenous origin and morphine-like activity.”(Zioudrou et al 1979)[15] In the years following this groundbreaking research,

researchers have measured the potency of exorphins, showing them to be comparable to morphine and enkephalin (Heubner et al. 1984), determined their amino acid sequences (Fukudome & Yoshikawa 1992), and shown that they are absorbed from the intestine (Svedburg et al.1985) and can produce effects such as analgesia and reduction of anxiety which are usually associated with poppy-derived opioids (Greksch et al.1981, Panksepp et al.1984). Mycroft et al. estimated that 150 mg of the MIF-1 analogue could be produced by normal daily intake of cereals and milk, noting that such quantities are orally active, and half this amount ‘has induced mood alterations in clinically depressed subjects’ (Mycroft et al. 1982). (Greg Wadley and Angus Martin 2000)[9, 18, 13, 19, 20, 21, 17]

With this understanding of how exorphins can affect the human body, and knowing that there is no consensus as to why early man adopted agriculture Wadley and Martin go on to propose a new theory on the origin of agriculture and civilization:

Cereals and dairy foods are not natural human foods, but rather are preferred because they contain exorphins. This chemical reward was the incentive for the adoption of cereal agriculture in the Neolithic. Regular self-administration of these substances facilitated the behavioural changes that led to the subsequent appearance of civilisation.

In the bicameral era man would experience hallucinations in novel/stressful situations so that an individual would know what to do, in this sense every man had a god that walked with him and could be experienced face to face; after man began eating wheat this increased various by-products of stress in the body so that the voices would appear intermittently or perhaps almost continuously in some people. Thus you can see how it could be said that ancient man walked with god and spoke with him face to face, because god was always there for him and he provided assistance in times of need; after eating the forbidden fruit man was separated from god because the voices began to be experienced randomly so they would no longer provide helpful commands. The people who were living at the time of the breakdown of the bicameral mind, the first people who had consciousness as we know it, left records of their interactions with god. As god receded from the mind of man like a tide which would never return, the words of the prophets of the Old Testament acted like a bridge which would allow others to cross the chasm which lay under the lost sea. The word of god had replaced the voice of god, but the ebbing tide left behind a hollow space for a new kind of mentality, one which would allow mankind to deal with complex societies which led to much more novelty than they’d ever been exposed to before. Thus, as the hallucinated voice had changed from producing commands distilled from stored-up, admonitory wisdom to what was probably a steady stream of matter-of-fact statements, musings, and reproachful rants, suddenly this voice was a stimuli which one could react to. Not only could the voice provide sudden verbal insight, or “inspiration” (as the now-changing god-side of the mind “breathed into” man), but one could also speak to it in the sense that as the voice (I want to specify here that as the voice occurred more often it would likely be perceived as less and less of an auditory hallucination which was “heard” and more as the god-side of the mind speaking to the man-side in an internal space which was still developing) says something like “look at that drawing, that’s not what the tower looked like” then the man could say “yes, the tower was not round.” So, in effect, we could bounce ideas off of this new structure as if it were another person– it has been said that two heads are better than one, and what amounts to two brains is perhaps the best. Over time, with an adjustment to the diet, the acquisition of new metaphorical language, and a changing social structure, the god-side of the mind became more of an analog space, a mind-space, where narratization occurred.


“Dubito, ergo cogito, ergo sum” is an expanded form of Descartes original “Dubito, ergo sum.” It was written by French literary critic, Antoine Léonard Thomas, in an award-winning 1765 essay in praise of Descartes.

I would like to thank Rabbi James Cohn and Carole Brooks Platt for reviewing this essay and providing helpful commentary. I would also like to thank musicians Angel Olsen and Will Oldham/Bonnie ‘Prince’ Billy for providing continued inspiration.

[1] Jaynes, J. (1976). The Origin of Consciousness in the Breakdown of the Bicameral Mind. Boston: Houghton Mifflin.

[2] Babylonian Talmud: Berachos 40a; Sanhedrin 70b. (500 CE)

[3] Kabbalah: Sefer Yetzirah (~1000 CE from earlier texts)

[4] Babylonian Talmud: Sanhedrin 70b. (500 CE)

[5] Babylonian Talmud: Bavli Ketubot 111b. (500 CE)

[6] Constantini, L. (1989). Plant Exploitation at Grotta dell’Uzzo, Sicily: New Evidence for the Transition from Mesolithic to Neolithic Subsistence in Southern Europe, in Harris, D. R. & Hillman, G. C., eds, Foraging and Farming: The Evolution of Plant Exploitation, Unwin Hyman, London.

[7] Cordain, L. (1999). Cereal Grains: Humanity’s Double-edged Sword. Evolutionary Aspects of Nutrition and Health: Diet, Exercise, Genetics and Chronic Disease, Vol 84, pg 19-73. Retrieved January 1, 2014, from

[8] Sinclair, A.J. & O’Dea, K. (1990). Fats in Human Diets Through History: Is the Western Diet out of Step?; in Wood JD, Fisher AV (eds): Reducing Fat in Meat Animals; pg 1-47. London, Elsevier Applied Science.

[9] Wadley, G. & Martin, A. (1993) The Origins of Agriculture: A Biological Perspective and a New Hypothesis. Australian Biologist 6: pg 96-105, June 1993. Retrieved January 1, 2014, from

[10] Bender, B. (1975) Farming in Prehistory: From Hunter-gatherer to Food Producer. John Baker, London.

[11] Adams, W.M. (1987) Cereals Before Cities Except After Jacobs, in M. Melko & L.R. Scott eds, The Boundaries of Civilizations in Space and Time, University Press of America, Lanham.

[12] Thatcher, J. P. (1987) The Economic Base for Civilization in the New World, in Melko, M. & Scott, L. R., eds, The Boundaries of Civilizations in Space and Time, University Press of America, Lanham.

[13] Fukudome, S., & Yoshikawa, M. (1992). Opioid Peptides Derived from Wheat Gluten: Their Isolation and Characterization. FEBS Letters (Federation of European Biochemical Societies), Vol 296, No 1; pg 107-111. Retrieved January 1, 2014, from

[14] Fukudome, S., & Yoshikawa, M. (1993). Gluten Exorphin C: A Novel Opioid Peptide Derived From Wheat Gluten. FEBS Letters (Federation of European Biochemical Societies), Vol 316, No 1; pg 17-19. Retrieved January 1, 2014, from

[15] Zioudrou, C., Streaty, R., & Klee, W. (1979). Opioid Peptides Derived from Food Proteins: The Exorphins. The Journal Of Biological Chemistry, Vol 254, No 7; pg 2446-2449. Retrieved January 1, 2014, from

[16] Brantl, V., Teschemacher, H., Henschen, A. & Lottspeich, F. (1979). Novel Opioid Peptides Derived from Casein (beta-casomorphins), Hoppe-Seyler’s Zeitschrift fur Physiologische Chemie, Vol 360; pg 1211-6.

[17] Mycroft, F. J., Wei, E. T., Bernardin, J. E. & Kasarda, D. D. (1982). MlF-like Sequences in Milk and Wheat Proteins. New England Journal of Medicine, Vol 301; pg 895.

[18] Heubner, F., Liebeman, K., Rubino, R. & Wall, J. (1984). Demonstration of High Opioid-like Activity in Isolated Peptides from Wheat Gluten Hydrolysates. Peptides, Vol 5; pg 1139-47.

[19] Svedburg, J., De Haas, J., Leimenstoll, G., Paul, F. & Teschemacher, H. (1985). Demonstration of Betacasomorphin Immunoreactive Materials in in-vitro Digests of Bovine Milk and in Small Intestine Contents After Bovine Milk Ingestion in Adult Humans. Peptides, Vol 6; pg 825-30.

[20] Greksch, G., Schweiger C., Matthies, H. (1981). Evidence for Analgesic Activity of Beta-casomorphin in Rats. Neuroscience Letters, Vol 27; pg 325-8.

[21] Panksepp, J., Normansell, L., Siviy, S., Rossi, J. & Zolovick, A. (1984). Casomorphins Reduce Separation Distress in Chicks. Peptides, Vol 5; pg 829-83.