In Plato's works, Socrates is presented as a kind of intellectual midwife who extracted knowledge already existent in the person he questioned. According to the doctrine of recollection, learning is only the remembering of knowledge possessed in a former life. In Phaedo, the second argument for the survival of the soul is that knowledge is recollection, and therefore the soul must have existed before birth.

Aristotle rejected the theory of inborn ideas and proposed the metaphorical tabula rasa, which was subsequently accepted in the seventeenth and eighteenth centuries by empirical physiologists, including Locke and Helv*!etius. The newborn mind was considered a blank tablet on which experience would write messages, and the dissmilarities between individuals were attributed solely to differences in education.

The Aristotelian principle, "Nihil est in intellectu quod no prius suent in sensu" (St. Thomas, De Veritatis, II, 3), repeated among others by Leonardo da Vinci ("Ogni nostra cognizioni principia dai sentimenti"), expressed the idea still prevalent in present times that "nothing is in the intellect which was not first in the senses." Some authors, including Epicurus and the sensualists, stressed the importance of sensory inputs to its limit, proposing that the intellect is only what is in our senses. Between the extremes of considering the mind either sophisticated

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or naive at birth, contemporary opinion holds that both genetic and experiential components are essential, although their functions and relative importance remain controversial. According to several child psychiatrists, heredity and experience are equipotent (156, 225). Piaget (178) has emphasized that while the human brain is an almost entirely hereditary regulatory organ, it has practically "no hereditary programming of these regulations, quite unlike the case of so many instincts in birds or fishes. . . ." Intelligence combines two cognitive systems: experience and endogenous regulations. The last system is a source of intellectual operations; by prolonging the feedbacks and correcting the mistakes, it transforms them into instruments of precognition.

The genetic determination of mental functions has been supported by Rainer (181), who believes that the fertilized ovum contains "the primordia of what we later call mind," and that "the newborn infant is already as much of an individual 'mentally' as he is physiognomically." According to the evolutionary theories of William James (119), "the new forms of being that make their appearance are really nothing more than results of the redistribution of the original and unchanging materials . . . the evolution of the brains, if understood, would be simply the account of how the atoms came to be so caught and jammed. In this story no new natures [James's emphasis], no factors not present at the beginning are introduced at any later stage."

In agreement with these ideas, Sherrington (206) writes: "Mind as attaching to any unicellular life would seem to me unrecognizable to observation; but I would not feel that permits me to affirm it is not there. Indeed, I would think that since mind appears in the developing soma, that amounts to showing that it is potential in the ovum (and sperm) from which the soma sprang. The appearance of recognizable mind in the soma would then be not a creation de novo but a development of mind from unrecognizable into recognizable."

The importance of the prenatal period as a determinant of future behavior crystallized in the concept of "ontogenetic zero"

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(88) has been accepted by most child psychologists (30). At the moment of fertilization, the life of a unique individual is initiated (at birth, a child is already nine months old); and some experts have suggested that its beginning should be traced back through evolution of the parental reproductive cells or even through previous generations.

These theories have the merit of stressing the role of genetics in the formation of the mind, but they give the false impression that genetic factors alone are able to create a mind, or that in some mysterious way, a minute, undeveloped mind already exists in the cells. At the core of this discussion is the meaning of "potentiality," which is a convenient concept provided that we understand its limitations. If we say "a block of marble is potentially a piece of sculpture," we mean that marble is an element which can be shaped into a symbolic pattern by using chisels and hammers with appropriate skills. We may say that all shapes and artistic creations potentially exist in the marble, but the reality is that in the absence of a sculptor, the piece of stone lacks, per se, the essential elements to become a work of art. It would be incorrect to think that tools or skills are hidden within the block of marble, or that if we waited long enough, a statue would emerge spontaneously from the block. This type of incorrect reasoning has been called the "error of potentiality" (137). It has infiltrated the field of embryology and has influenced analyses of the origin and evolution of mental functions by assuming, at a certain stage of development, the existence of properties which are present only at a later stage and which depend on a series of essential conditions neither present in nor determined by the stage under consideration.

If we say that the mind is in the sperm, we can also say that each man has one million children, that a newborn baby will be the inventor of spaceships, or that a worm may evolve into a monkey. These statements may be potentially valid, but their fulfillment is contingent upon a constellation of factors which are not present in the original material. In spite of his genes and his potentials, a man cannot create a single child without

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the collaboration of a woman; and a baby will not invent rockets unless he is exposed to a highly sophisticated level of physics. We believe that worms have evolved into more complex forms of life, and that potentially they may produce dinosaurs, supermen, or inhabitants of the moon, but before we allow our imagination to wander among the limitless possibilities of nature, it is preferable to identify the factors responsible for the observed reality among an infinite number of theoretical potentials.

According to early theories of preformism, the germinal cell—the ovum—held a miniature organism with microscopic eyes, arms, legs, and other parts of the body which eventually would grow. The ovaries of Eve had potentially the bodies—and minds —of all mankind. As soon as scientific embryology began, it was evident that the germinal cell did not contain a compressed homunculus, but only a plan which required the interaction of other elements in order to develop into a human being.

A relatively small group of organization centers (the genes), with the collaboration of molecules supplied from the outside (the mother), produce another series of organizers (enzymes, hormones, and other active substances) which will arrange patterns of molecules for the construction of cells, tissues, and organs and will also produce a new series of organizers to direct the interaction of these new elements. The organizers are not completely stereotyped in performance but are influenced by their medium. A particular gene may have different phenotypic effects in different environments, and "genes control the 'reaction norm' of the organism to environmental conditions" (31). Blood vessels, muscles, and the various organs are differentiated; neurons appear, their interconnections are established, and the brain evolves. Chromosomes have neither heart nor brain—only a set of architectonic plans which under suitable conditions will evolve into a complete organism. These plans are unfulfilled tor millions of sexual cells and for countless embryos that are casualties in spontaneous abortions. The possibilities of evolution are far from accomplished realities.

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If we accept these ideas, we may also state that the fecundated germinal cell does not talk, understand, or think, and that the resulting embryo has no mental functions before the medullary plate rolls up to form the neural tube. When can we detect the first signs of a functioning mind? How are they correlated with the anatomical development of the central nervous system? The study of these questions may be simplified if we first examine the initial signs of a functioning brain as revealed by behavioral expression in lower animals. Before the development of muscles, motor neurons are already growing out to establish neural contacts with them. The order of growth is a "progressive individualism within a totally integrated matrix, and not a progressive integration of primarily individuated units" (34). Motions, therefore, are basically a part of a total pattern, and their relative individualization is only a secondary acquisition. Some efferent motor pathways appear before any afferent fiber enters the cerebrum. Initially, the cerebral association system develops toward the motor system and the peripheral sensory fibers grow toward the receptor field. Significant conclusions from these facts are that "the individual acts on its environment before it reacts to its environment" (35), that efferent nerves must be stimulated by products of the organism's metabolism, and that "behavior in response to such stimulation is spontaneous in the sense that it is the expression of the intrinsic dynamics of the organism as a whole" (37). Total behavior is not made up of reflexes; rather, "the mechanism of the total pattern is an essential component of the performance of the part, i.e., the reflex," and behavior therefore "cannot be fully expressed in terms of S-R (Stimulus-Response)" (37). It is significant that in man vestibular connections develop before vestibular sense organs, because this reveals that "the cerebral growth determines the attitude of the individual to its environment before that individual is able to receive any sensory impression of its environment. Hence, the initiative is within the organism" (36).

Some of these findings have been confirmed in the toadfish and the cunner (228). On the first day that the cunner larva

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swim around freely, they do not respond to external stimuli. Thus under natural conditions, this species moves about without an effective exteroceptive mechanism, evidently propelled by a "mechanism of motility activated from within." The afferent sensory system grows gradually until it finally "captures" the primitive motor system. The conclusion is that behavior has two components: "endogenous activity, the fundamental motility conditioned by the inner physiological adjustments of the organism; and exogenous activity, the oriented activity by which endogenous activity is so modified as to render response to external stimuli possible" (70).

This information emphasizes the importance of genetic determination and indicates that some mechanisms for behavorial performance are organized in the absence of environmental inputs. It is generally accepted that development of the nervous system is basic for the onset and elaboration of mammalian behavior, but it is not clear whether any factor can be singled out as decisive. Without synaptic conduction, impulses obviously cannot be transmitted: thus the functional maturity of synapsis must be essential (104, 144, 205, 241). Objections have been raised about the acceptance of synaptic permeability as the main reason for onset of behavior (140), and other factors may be equally important. Activity of peripheral nerve fibers is considered essential for the differentiation and specificity of behavioral performance (72, 78), and the anatomical development of neurofibrillae may be specifically related to the onset of behavior (136). These and other studies have provided important information, but its interpretation has often been biased by methodological distortions.

It is a common error in behavioral embryology, and in science generally, to try to simplify the observed phenomena and to reduce causality to a single factor, excluding all other variables. This is the fallacy of the single cause (121), or failure to understand that a biological phenomena is always the product of a complex situation, not of a single determinant. With this pitfall in mind, we must face the task of identifying the several

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elements essential for the development of any given phenomenon, and both conduction and synaptic mechanisms are certainly basic for the onset of behavior.

Myelin is a substance with insulating properties covering the nerves, and its appearance in neuronal sheaths has often been associated with the onset and differentiation of behavior by neuroanatomists. A correlation perhaps exists for some specific behavior patterns in the cat and the opossum (138, 226), but most authors today agree that the myelogenetic law cannot be generalized. In the newborn rat, myelination does not take place for several days although the fetus starts moving many days before birth, and some discrete reflexes and inhibitory activity in higher centers can be observed in a rat fetus nineteen days after conception (5). Myelination, therefore, cannot be interpreted as necessary for the conduction of impulses or for functional insulation.

Differences in anatomical and behavioral evolution certainly exist between mammals and lower life forms. In the guinea pig, for example, limbs are well formed in the embryo before appearance of the first behavioral response, while in the salamander motor behavior is initiated before morphological differentiation of the limbs. Evidently embryologic studies of man cannot be as extensive and as well controlled as those of amphibia, but valuable information on this subject already exists (30). Inside the uterus, the human embryo has a comfortable and sheltered life without facing responsibilities or making choices. Cells multiply automatically and organs take shape while the growing fetus floats weightless in the silent night of amniotic fluid. Food and oxygen are provided and wastes are removed continuously and effortlessly by the maternal placenta. As the fetus grows, many organs perform something like a dress rehearsal before their functions are really required. This is usually referred to as the principle of anticipatory morphological maturation. The heart starts to beat when there is no blood to pump; the gastrointestinal tract shows peristaltic movements and begins to secrete juices in the absence of food; the eyelids

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open and close in the eternal darkness of the uterus; the arms and legs move, giving the mother the indescribable joy of feeling a new life inside herself; even breathing movements appear several weeks before birth when there is no air to breathe (1).

Some extensive information about human fetal behavior has been obtained by indirect methods in pregnant women, while other findings were obtained directly from fetuses surgically removed for medical reasons (112, 155, 176). The first movement observed in a four-millimeter-long, three-week-old fetus is the heart beat, which has intrinsic determinants because it starts before the organ has received any nervous connections. The neural elements needed for a reflex act can be demonstrated in the spinal cord at the second month of embryonic life, and at that time, cutaneous stimulation may induce motor responses. A fourteen-week fetus shows most of the responses which can be observed in the neonate with the exception of vocalization, the tonic grasping reflex, and respiration. With fetal growth, spontaneous motility increases inside the mother's womb and it is well known that responses from the fetus may be elicited by tapping the mother's abdominal wall.

Sensory perception of the fetus has been investigated in detail by several scientists (27, 30, 240). Cutaneous reception is well developed long before birth, and mechanical or thermal stimulation of the skin elicits appropriate motor activity related to the stimulated area. The existence of pain perception is doubtful. Proprioceptors of the muscles (the spindles) develop at the fourth month of fetal life, and the labyrinth is evident even earlier. Both organs are active during fetal life; they are capable of postural adjustments and may be partially responsible for fetal motility in the uterus.

The possibility of fetal perception of gastrointestinal movements, hunger, thirst, suffocation, and other types of organic experience has been debated, and it is generally accepted that internal stimuli may activate skeletal musculature. Distinction of sweet from other tastes and of unpleasant odors such as asafetida has been demonstrated in premature babies, showing

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that these receptor mechanisms are already developed. It is doubtful, however, that with the nose and mouth immersed in amniotic fluid, the fetus could have gustatory or olfactory experiences before birth.

The auditory apparatus is well developed at birth, but the general consensus (180) is that the infant is deaf until the liquid of the fetal middle ear is drained through the Eustachian tube by breathing, crying, and perhaps yawning. Loud noises, however, might be perceived, and some cases of presumed fetal hearing have been reported (79).

The optic apparatus is sufficiently developed in the newborn infant to permit perception of light and darkness, but the optic nerve is not yet fully developed, and its evolution continues after birth and is probably influenced by sensory perception (180). It is highly improbable that the fetus has any visual experience during its uterine life.

In summary, it is unlikely that before the moment of birth the baby has had any significant visual, auditory, olfactory, or gustatory experience, and it is probable that it has received only a very limited amount of tactile, organic, and proprioceptive information. The newborn has an elaborated system of reflexes; and coughing, sneezing, sucking, swallowing, grasping, and other actions may be evoked by the appropriate sensory stimulation. In an experimental study of seventeen behavioral responses, their intercorrelations proved to be zero, indicating that "there is no mental integration in the newborn child" (82). This integration usually takes place during the first postnatal month.

Whether or not the fetus was capable of conscious experience was a classical philosophical and psychological problem debated at length with a flourish of words and speculations but with little factual support (39, 86, 135, 147, 175). It is difficult to understand the basis of this controversy since there is no evidence that the fetus has visual, auditory, olfactory, or gustatory stimulation. The possibility of fetal awareness is therefore reduced to a limited input of organic sensations of proprioception and touch in the absence of the main sensory faculties. Whether

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or not these phenomena can by themselves create consciousness is mainly a question of definition and arbitrary agreement, but it may be stated that they cannot produce manifestations comparable to those of consciousness in children or adults, which are mainly based on visual and auditory perception and experience. The mystery is perhaps insoluable due to the impossibility of establishing verbal communication with the newborn.

Anticipatory morphological maturation is present in various mechanisms which remain quiescent in the fetus, ready to perform with physiological efficiency as soon as they are needed. Their necessary links are established before birth and are triggered by appropriate stimulation. These functions, which include oral suction, respiration, kidney secretion, and gastrointestinal activity, are able to act several weeks before an expected delivery, in case the baby is born prematurely.

No comparable provisions exist for mental functions. The newborn brain is not capable of speech, symbolic understanding, or of directing skillful motility. It has no ideas, words, or concepts, no tools for communication, no significant sensory experience, no culture. The newborn baby never smiles. He is unable to comprehend the loving phrases of his mother or to be aware of the environment. We must conclude that there are no detectable signs of mental activity at birth and that human beings are born without minds. This statement may seem startling, but it should not be rejected by saying, "Well, you don't see mental functions during the first few days, but everything is ready for action; wait a few weeks, or perhaps a few months; it is just a slight lack of maturity, but the baby's mind is there." Potentiality should not be confused with reality. A project is not an accomplished fact, especially when essential elements are lacking in the original design. Naturally a baby lacks experience, but by recognizing this fact, we are accepting the essentiality of extracerebral elements which originate in the outside world and are independent of both the organism and its genetic endowment. As Cantril and Livingston (29) have said, organisms are in a constant "transaction," in a "process

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of becoming," constantly changing into something different from what they were before. Early in life, an infant is attracted to sources of comfort and repelled by sources of distress. These experiences lead to the "intelligent" recognition of objects and persons associated with positive or negative reinforcement, and they will determine selective patterns of behavioral response. "It is at this point, we think, that 'mind' is born" (29).

The concept of the mindless newborn brain is a useful hypothesis because it clarifies our search for the origin of the mind. If this origin depended on genetic endowment, then mental functions should appear in the absence of other external elements (as respiratory functions do). If genetic determination alone is not sufficient, then we must investigate the source and characteristics of the extracerebral elements responsible for the appearance of the mind as the baby matures.