Herzen ^ found a marked reduction of reaction time for both girls and boys at puberty. His table is as follows: GROWTH OF MOTOR POWER AND FUNCTION 153 Age.
Boys.
Girls.
lO-IS, ■ Foot,.4CX) ^ After 15 • From this it appears that young girls react quickest, and Marro ^ thinks that they often reach a high point and are either arrested rather suddenly in rate or often decline from a high point which they can not maintain and develop no further through life. This, he says, may be due to the low- ered rate of oxidation characteristic of this age, and which, if marked, may cause hysteria, or it may be due to the greater distraction of attention which makes the concentration of mind necessary for this test now harder.
At Chicago, quickness of reaction to a signal was found to increase rapidly to eight years, when for a year the increment was less, followed by another rise for both sexes to twelve. Then there was no gain for boys to fourteen and little for girls; a rapid increase of both to sixteen, with no gain the following year.
The time of thought required for a reaction, plus the two mental processes of discrimination and choice, showed a rather steady increase to ten; then a positive loss for a year to twelve in girls; then a rather steady increase to thirteen in boys, followed by a year of loss. Girls increased rapidly from thirteen to fourteen, and boys from fourteen to fifteen, after which the rate of increase was less for girls and very slight indeed for boys.
Here, too, may be mentioned the studies of Seashore,^ who found that children were able to reproduce small time inter- vals of about five seconds pretty accurately at all ages from six to fifteen. Intervals of ten seconds were shortened to 8.2, those of twenty to 14.4, and those of thirty to 13.5. From eight or nine years on the improvement in reproducing the longer intervals rapidly increased.
• Studies in Psychology. University of Iowa, 1899.
154 THE PSYCHOLOGY OF ADOLESCENCE Adolescence marks a new relation to time and space. The temporal and spatial horizon is enlarged; greater wholes are more adequately judged; more complex members of each are grouped into unity; the relation of wholes and parts is better seen. This we shall see more fully in the chapters on mental development.
To understand the momentous changes of motor func- tions that characterize adolescence we must consider other than the measurable aspects of the subject. Perhaps the best scale on which to measure all normal growth of muscle structure and functions is found in the progress from funda- mental to accessory. The former designates the muscles and movements of the trunk and large joints, neck, back, hips, shoulders, knees, and elbows, sometimes called central, and which in general man has in common with the higher and larger animals. Their activities are few, mostly simultane- ous, alternating and rhythmic, as of the legs in walking, and predominate in hard-working men and women with little cul- ture or intelligence, and often in idiots. The latter or acces- sory movements are those of the hand, tongue, face, and articu- latory organs, and these may be connected into a long and greatly diversified series, as those used in writing, talking, piano-playing. They are represented by smaller and more nu- merous muscles, whose functions develop later in life and repre- sent a higher standpoint of evolution. Those smaller muscles for finer movements come into function later and are chiefly associated with psychic activity, which plays upon them by incessantly changing their tensions, if not causing actual movement. It is these that are so liable to disorder in the many automatisms and choreic tics we see in school chil- dren, especially if excited or fatigued. General paralysis usu- ally begins in the higher levels by breaking these down, so that the first symptom of its insidious and never interrupted progress is inability to execute the more exact and delicate movements of tongue or hand, or both. Starting with the latest evolutionary level, it is a devolution that may work down- ward till very many of the fundamental activities are lost be- fore death. ' Nothing better illustrates this distinction than the differ- GROWTH OF MOTOR POWER AND FUNCTION 155 ence between the fore foot of animals and the human hand. The first begins as a fin or paddle or is armed with a hoof, and is used solely for locomotion. Some carnivora with claws use the fore limb also for holding as well as tearing, and others for digging. Arboreal life seems to have almost created the simian hand and to have wrought a revolution in the form and use of the forearm and its accessory organs, the fingers. Apes and other tree-climbing creatures must not only adjust their prehensile organ to a wide variety of distances and sizes of branches, but must use the hands more or less freely for picking, transporting, and eating fruit, and this has probably been a prime factor in lifting man to the erect posi- tion, without which human intelligence as we know it could have hardly been possible. " When we attempt to measure the gap between man and the lower animals in terms of the form of movement, the wonder is no less great than when we use the term of mentahty." ^ The degree of approximation to human intelligence in anthropoid animals follows very closely the degree of approximation to human movements.
The gradual acquirement of the erect position by the human infant admirably repeats this long phylogenetic evolu- tion.^ At first the limbs are of almost no use in locomotion, but the fundamental trunk muscles with those that move the large joints are more or less spasmodically active. Then comes creeping, with use of the hip muscles, while all below the knee is useless, as also are the fingers. Slowly the leg and foot are degraded to locomotion, slowly the great toe be- comes more limited in its action, the thumb increases in flexibility and strength of opposition, and the fingers grow more mobile and controllable. As the body slowly as- sumes the vertical attitude, the form of the chest changes till its greatest diameter is transverse instead of from front to back. The shoulder-blades are less parallel than in quadrupeds, and spread out till they approximate the same plane. This gives the arm freedom of movement laterally, so that it can be rotated one hundred and eighty degrees in man as contrasted to one hundred degrees in apes, thus giving man the command J F. Burk in From Fundamental to Accessory. Pedagogical Lessons, vol. i, p. 29 'Creeping and Walking, by A. VV. Trettien. Am. Jour, of Psychol., Oct., 1900 15^ THE PSYCHOLOGY OF ADOLESCENCE of almost any point within a sphere of which the two arms are radii.
On the principle of heterogeny, by which movements as well as structures are carried on, but transferred to higher levels, grasping was partly developed from and partly added to the old locomotor function of the fore limbs; the jerky automatisms as well as the slow rhythmic flexion and exten- sion of finger and hand, early aimless reflexes, survivals of arboreal and perhaps even earlier aquatic life, are coordi- nated, and the bilateral, simultaneous, and rhythmic mode of movenlents so characteristic of larger fundamental parts is supplemented by superposed systems of exact and complex serial activities, which are less determined by heredity as ancestral currents grow shallow and uncertain near the end of the growth period. In a sense, a child or man is the sum total of his movements or tendencies to move, and nature and instinct chiefly determine the basal, and education the acces- sory parts of our activities.
The entire accessory system is thus of vital importance for the development of all of the arts of expression. These smaller muscles might almost be called organs of thought. Their tension is modified with the faintest change of soul, such as is seen in accent, inflection, facial expressions, hand- writing, and many forms of so-called mind-reading, which, in fact, is always muscle-reading. The day-laborer of low intel- ligence, with a practical vocabulary of not over five hundred words, who can hardly move each of his fingers without moving others or all of them, who can not move his brows or corru- gate his forehead at will, and whose inflection is very monoto- nous, illustrates a condition of arrest or atrophy of this later, finer, accessory system of muscles. On the other hand, the child, precocious in any or all of these later respects, is very liable to be undeveloped in the larger and more fun- damental parts and functions. The full unfoldment of each is, in fact, an inexorable condition precedent for the normal development to full and abiding maturity of the higher and more refined muscularity, just as conversely the awkward- ness and clumsiness of adolescence mark a temporary loss of balance in the opposite direction. If this general conception be correct, then nature does not finish the basis of her pyra- GROWTH OF MOTOR POWER AND FUNCTION 157 mid in the way Ross, Mercier, and others have assumed, but lays a part of the foundation, and, after carrying it to an apex, normally goes back and adds to the foundation to carry up the apex still higher, and if prevented from so doing, expends her energy in building the apex up at a sharper angle till instability results. School and kindergarten often lay a disproportionate strain on the tiny accessory muscles, weigh- ing altogether but a few ounces, that wag the tongue, move the pen, and do fine work requiring accuracy. But still at this stage prolonged work requiring great accuracy is irksome and brings dangers homologous to those caused by too much fine work in the kindergarten before the first adjustment of large to small muscles, which lasts until adolescence, is estab- lished. Then disproportion between function and growth often causes symptoms of chorea. The chief danger is arrest of the development and control of the smaller muscles. Many occupations and forms of athletics, on the contrary, place the stress mainly upon groups of fundamental muscles to the neglect of finer motor possibilities. Some who excel in heavy athletics no doubt coarsen their motor reactions, be- come not only inexact and heavy, but unresponsive to finer stimuli, as if the large muscles were hypertrophied and the small ones arrested. On the other hand, many young men, and probably more young women, expend too little of their available active energy upon basal and massive muscle work, and cultivate too much, and above all too early, the delicate responsive work. This is, perhaps, the best physiological char- acterization of precocity, and issues in excessive nervous and muscular irritabiHty. The great influx of muscular vigor that unfolds during adolescent years and which was origi- nally not only necessary to successful propagation, but an expression of virility, seems to be a very plastic quantity, so that motor regimen and exercise at this stage is probably more important and all-conditioning for mentality, sexual- ity, and health than at any other period of life. Intensity and for a time a spurty diathesis is as instinctive and desirable as are the copious minor automatisms which spontaneously give the alphabet out of which complex and finer motor series are later spelled by the conscious will. Mercier and others have pointed out that, as most skilled labor, so school 158 THE PSYCHOLOGY OF ADOLESCENCE work and modern activities in civilized life generally lay pre- mature and disproportionate strains upon those kinds of move- ment requiring exactness. Stress upon basal movements is not only compensating, but is of higher therapeutic value against the disorders of the accessory system; it constitutes the best cure or prophylactic for fidgets and tense states, and directly develops poise, control, and psycho-physical equilib- rium. Even when contractions reach choreic intensity the best treatment is to throw activities down the scale that meas- ures the difference between primary and secondary move- ments and make the former predominate.
The number of movements, the frequency with which they are repeated, their diversity, the number of combinations, and their total kinetic quantum in young children, whether we consider movements of the body as a whole, fundamental movements of large limbs, or finer accessory motions, is amazing. Nearly every external stimulus is answered by a motor response. Dresslar ^ observed a thirteen months old baby for four hours, and found, to follow Preyer's classifi- cation, impulsive or spontaneous, reflex, instinctive, imita- tive, inhibitive, expressive, and even deliberative movements, with marked satisfaction in rhythm, attempts to do almost anything which appealed to him, and almost inexhaustible efferent resources. A friend has tried to record every word uttered by a four-year-old girl during a portion of a day, and finds nothing less than verbigerations. A teacher noted the activities of a fourteen-year-old boy during the study time of a single school day,^ with similar results.
Lindley^ studied 897 common motor automatisms in children, which he divided into 92 classes: 45 in the region of the head, 20 in the feet and legs, 19 in the hands and fin- gers. Arranged in the order of frequency with which each was found the list stood as follows: fingers, feet, lips, tongue, head, body, hands, mouth, eyes, jaws, legs, forehead, face, arms, ears. In the last five alone adolescents exceeded children, the latter excelling the former most in those of head and mouth, legs and * A Morning Observation of a Baby. Ped. Sem., Dec, 1901. ' Kate Carman. Notes on School Activity. Ped. Sem., March, 1902. ^ A Preliminary Study of Some of the Motor Phenomena of Mental Effort. Am. Jour, of Psy.jvol. vii, p. 491.
GROWTH OF MOTOR POWER AND FUNCTION 159 tongue, in this order. The writer beheves that there are many more automatisms than appeared in his returns.
School Hfe, especially in the lower grades, is a rich field for the study of these activities. They are familiar as lick- ing things, clicking with the tongue, grinding the teeth, scratching, tapping, twirling a lock of hair or chewing it, •biting the nails (Berillon's onychopbagia), shrugging corru- gations, pulling buttons or twisting garments, strings, etc., twirling pencils, thumbs, rotating, nodding and shaking the head, squinting and winking, swaying, pouting and grima- cing, scraping the floor, rubbing hands, stroking, patting, flicking the fingers, wagging, snapping the fingers, snufiling, squinting, picking the face, interlacing the fingers, cracking the joints, finger plays, biting and nibbling, trotting the leg> sucking things, etc.
The average number of automatisms per loo children Smith found to be 176, in adolescents no. Swaying is chiefly with children; playing and drumming with the fingers is more common among adolescents; the movements of fingers and feet decline little with age, and those of eyes and forehead increase, which is significant for the development of attention. Girls excel greatly in swaying, and also, although less, in finger au- tomatism, and boys lead in movements of tongue, feet, and hands. Such movements increase with too much sitting inten- sity of effort, such as to fix attention, and vary with the nature of the activity willed, but involve few muscles directly used in a given task. They increase up the kindergarten grades and fall off rapidly in the primary grades; are greater with tasks requiring fine and exact movements than with those involving large movements. Automatisms are often a sign of the difficulty of tasks. The restlessness that they often express is one of the commonest signs of fatigue. They are mostly in the accessory muscles, while those of the fundamental muscles (body, legs, and arms) disappear rapidly with age; those of eye, brow, and jaw show greatest increase with age, but their frequency in general declines with growing maturity, although there is increased frequency of certain specialized contractions, which indicate the gradual settling of expression in the face.
Often such movements pass over by insensible gradation i6o THE PSYCHOLOGY OF ADOLESCENCE into the morbid automatism of chorea, and in yet lower levels of decay we see them in the aimless palpation of the sick, in pselaphesis, carphology, and floccilation. In idiots^ arrest of higher powers often goes with hypertrophy of these move- ments, as seen in head-beaters (as if, just as nature impels those partially blind to rub the eyes for " light-hunger," so it prompts the feeble-minded to strike the head for cerebra- tions), rockers, rackers, shakers, biters, etc. Movements often pass to fixed attitudes and postures of limbs or body, disturb- ing the normal balance between flexors and extensors, the sig- nificance of which as nerve signs or exponents of habitual brain states and tensions Warner has so admirably shown. These non-volitional movements of earliest infancy and of later childhood are thus sure to become centers of intense and deep scientific interest in the near future. They are one of the richest of all the paleopsychic fields. I think we may regard most of them as rudimentary impulses to do acts which in some prehuman stage were of all-conditioning im- portance for life. They are not anticipatory of future useful activities, as Groos says they are, so much as relics of past forms of utilities now essentially obsolete. Ancient modes of locomotion, prehension, balancing, defense, attack, sensual- ity, etc., are all rehearsed, some quite fully and some only by the faintest mimetic suggestion, flitting spasmodic ten- sions, gestures, or facial expressions. These motor odds, ends, and titbits often suggest therotropic or regressive acts of an almost saurian age, like the swimming movements of young infants, old modes of climbing, hitting, fighting, hunting. A few that were once accessory now seem fundamental, but with more the converse seems true. Each one of them is rich in suggestions now tantalizingly unverifiable. When we ap- proach the origin of vertebrate life, they are mementoes of the highest scientific value, and in their sign language, which now seems jargon, genetic psychology will one day read its title clear to pedigrees that are lost, while their further record and analysis by the refined methods now available is one of the richest of the many new fields opened by child study. They are motor analogues of the stray, segregated psychoses that * G. E. Johnson. Psychology and Pedagogy of Feeble-Minded Children. Ped GROWTH OF MOTOR POWER AND FUNCTION i6l make the subconscious activities now beginning to be studied. Both are largely vestigial and perhaps semi feral. They are the partly lapsed and unreclaimed, partly vir- gin and never cultivated Bad Lands of the state of Man-Soul, and if their area becomes too extensive or their growth too rank and noxious, may become a source of danger, but they always suggest larger possibiHties of human nature when we know how to make motor education utilize them aright. Thus it is with movements a little as Taine thought it was with impressions and ideas, which tend to grow to delusional intensity unless checked and balanced by others and wrought into the thought plexus of true perception and reason. This view I believe to be essentially new, and if true, its practical applications are important and its theo- retical implications yet more so.
Abundance and vigor of these movements are desirable and even a considerable degree of restlessness is a good sign in young children. Many of what are now often called nerve signs and even choreic symptoms, the fidgetiness in school on cloudy days and often after a vacation, the motor superfluities of awkwardness, embarrassment, extreme effort, excitement, fatigue, sleepiness, etc., are simply the forms in which we re- ceive the full momentum of heredity, and mark a natural rich- ness of the raw material of intellect, feeling, and especially of will. Hence they must be abundant. All parts should act in all possible ways at first and untrammeled by the activity of all other parts and functions. Some of these activities are more essential for growth in size than are later and more conscious movements. Here as everywhere the rule holds that powers themselves must be unfolded before the ability to check or even to use them can develop. All movements arising from spon- taneous activity of nerve cells or centers must be made in order even to avoid the atrophy of disease. Not only so, but this purer kind of innateness must often be helped out to some ex- tent in some children by stimulating reflexes; a rich and wide repertory of sensation must be made familiar; more or less and very guarded, watched and limited experiences of hunger, thirst, cold, heat, tastes, sounds, smells, colors, brightnesses, tactile irritations, and perhaps even occasional tickling and pain to play off the vastly complex function of laughing, crving, 12 1 62 THE PSYCHOLOGY OF ADOLESCENCE etc., may in some cases be judicious. Conscious and uncon- scious imitation or repetition of every sort of copy may also help to establish the immediate and low-level connection be- tween afferent and efferent processes that brings the organism into direct rapport and harmony with the whole world of sense. Perhaps the more rankly and independently they are devel- oped to full functional integrity, each in its season, if we only knew that season, the better. Premature control by higher cen- ters, or coordination into higher compounds of habits and or- dered serial activities, is repressive and wasteful, and the mature will of which they are components, or which must at least domesticate them, is stronger and more forcible if this serial stage is not unduly abridged.
But, secondly, many, if not most, of these activities when developed a little, group after group, as they arise, must be con- trolled, checked, and organized into higher and often more serial compounds. The inhibiting functions are at first hard. In trying to sit still the child sets its teeth, holds the breath, clinches its fists and perhaps makes every muscle tense with a great effort that very soon exhausts. This repressive function is probably not worked from special nervous centers, nor can we speak with confidence of collisions with " sums of arrest " in a sense analogous to that of Herbart, or of stimuli that normally cause catabolic molecular processes in the cells, being mysteri- ously diverted to produce increased instability or anabolic labil- ity in the sense of Wundt's Mechanik der Nerven. The concept now suggested by many facts is that inhibition is irradiation or long circuiting to higher and more complex brain areas, so that the energy, whether spontaneous or reflex, is diverted to be used elsewhere. These combinations are of a higher order, more remote from reflex action, and modified by some Jacksonian third level, or perhaps in part by Vulpius' transverse layer. Action is now not from independent centers, but these are slowly associated, so that excitation may flow off from one point to any other and any reaction may result from any stimulus.
The more unified the brain the less it suffers from localiza- tion, and the lower is the level to which any one function can exhaust the whole. The tendency of each group of cells to dis- charge or overflow into those of lower tension than themselves increases as correspondence in time and space widens. The GROWTH OF MOTOR POWER AND FUNCTION 163 more one of a number of activities gains in power to draw on all the brain, or the more readily the active parts are fed at cost of the resting parts, the less is rest to be found in change from one of these activities to another, and the less do concentra- tion and specialization prove to be dangerous. Before, the aim was to wake all parts to function; now it is to connect them. Intensity of this cross-section activity now tends to unity, so that all parts of the brain energize together. In a brain with this switch-board function well organized, each reaction has grown independent of its own stimulus and may result from any stimulation, and each act, e. g., a finger movement of a peculiar nature, may tire the whole brain. This helps us to un- derstand why brain-workers so often excel laborers not only in sudden dynamometric strength test, but in sustained and long- enduring effort. In a good brain or in a good machine, power may thus be developed over a large surface, and all of it applied to a small one, and hence the dangers of specialization are lessened in exact proportion as the elements of our ego are thus compacted together. It is in the variety and delicacy of these combinations and all that they imply, far more than in the ele-