Why Do Babies Move Arms and Legs So Much
Proc Natl Acad Sci U Due south A. 1998 Nov x; 95(23): 13982–13987.
Psychology
Move analysis in infancy may exist useful for early diagnosis of autism
Philip Teitelbaum
Departments of *Psychology and ‡Child Psychiatry, University of Florida, Gainesville, FL 32611
Osnat Teitelbaum
Departments of *Psychology and ‡Kid Psychiatry, University of Florida, Gainesville, FL 32611
Jennifer Nye
Departments of *Psychology and ‡Kid Psychiatry, University of Florida, Gainesville, FL 32611
Joshua Fryman
Departments of *Psychology and ‡Child Psychiatry, Academy of Florida, Gainesville, FL 32611
Ralph G. Maurer
Departments of *Psychology and ‡Kid Psychiatry, University of Florida, Gainesville, FL 32611
Abstract
All of the 17 autistic children studied in the nowadays paper showed disturbances of move that with our methods could be detected clearly at the age of 4–six months, and sometimes fifty-fifty at birth. We used the Eshkol–Wachman Movement Analysis System in combination with still-frame videodisc analysis to study videos obtained from parents of children who had been diagnosed as autistic by conventional methods, usually around three years old. The videos showed their behaviors when they were infants, long before they had been diagnosed as autistic. The movement disorders varied from child to child. Disturbances were revealed in the shape of the mouth and in some or all of the milestones of development, including, lying, righting, sitting, crawling, and walking. Our findings back up the view that movement disturbances play an intrinsic part in the miracle of autism, that they are present at birth, and that they can be used to diagnose the presence of autism in the start few months of life. They indicate the need for the development of methods of therapy to be applied from the beginning few months of life in autism.
In that location is controversy over whether movement disorders play a central part in the phenomenon of autism and even whether such move disorders be in autism at all. For case, Rimland (1) has stated:
It has been widely recognized for many decades that the vast majority of autistic persons are quite unimpaired with regard to their finger dexterity and gross motor capabilities. They have in fact oftentimes been described equally especially dexterous and coordinated. The literature abounds with stories of immature autistic children who tin can take apart and reassemble small mechanical devices, build towers of blocks and dominos higher than a normal adult can, assemble jigsaw puzzles and climb to dangerously loftier places without falling… The idea that autism is, or typically involves, a "move disorder" is just ludicrous … .
On the other hand, Damasio and Maurer (2) and Vilensky et al. (three) showed that autistic children between the ages of iii and ten walk somewhat similar Parkinsonian adults in that they walk more than slowly than normal, with shorter steps. Correspondingly, Courchesne et al. (4), using MRI, have shown that certain areas of the cerebellar vermis are incompletely developed in autistic children [but encounter Piven (5)]. This also supports the view that movement disorders might play a role in autism (half-dozen, seven).
We believe that the findings presented here aid to resolve this controversy. We used Eshkol–Wachman Motion Analysis in combination with flicker-free light amplification by stimulated emission of radiation-disc still-frame analysis to study videos taken in infancy of 17 children who later turned out to be autistic, every bit diagnosed at the age of 3 years or older past conventional methods of diagnosis. Every one of these children displayed movement disorders, some subtle, some obvious.
Furthermore, because these movement disorders always could exist detected with our methods as early as 4–6 months of age and sometimes as early as the kickoff few days subsequently birth, we suggest that the study of movement disorders in infancy may serve as an earlier indicator than presently available methods for diagnosing autism in children.
As a framework for the written report of infant movement, we decided to analyze the movements involved in the major motor milestones in the evolution of the baby from nascence through the time that he or she starts to walk: i.e., lying, righting, sitting, crawling, standing, and walking. Every child goes through these stages (infants with astringent neurological defects who are unable to progress through these stages of development are not included in the present discussion). Therefore, these motor milestones tin serve as a common denominator past which to evaluate and compare normal and disintegrated movement in infants.
METHODS
We advertised in the monthly periodical published by the National Commission on Autism and in the electronic mail list run by the Autism Club of America. We asked parents of autistic children (diagnosed by conventional methods usually at three years or older) to transport us videos of their children taken when they were infants. We received and copied videos of 17 such infants and compared their patterns of lying (decumbent and supine), righting from their back to their stomach, sitting, crawling, continuing, and walking with that of 15 normal infants. The normal infants were filmed by united states in the nurseries of Kibbutz Merhavia in Israel when each pattern was just beginning to develop. Selected portions of these behaviors were transferred to videodisc (Panasonic Rewritable Optical Disc Recorder LQ-4000, Secaucus, NJ) for still-frame analysis past using Eshkol–Wachman Movement Note (8). Eshkol–Wachman Movement Notation is a general analysis system in which spherical coordinates are applied independently to each segment of the torso. By distinguishing betwixt which segments are actively moving versus those that are being carried passively along, a deeper agreement of abnormal motion is possible.
RESULTS
Motor Milestones in Development
Lying.
Lying is an active posture, even in the first few days of life. As has been pointed out by Casaer (9), a newborn infant maintains specific agile postures while lying. Persistent deviations from the normal patterns of lying tin can indicate abnormalities associated with autism. For example, 1 of the children in the nowadays report showed a persistent asymmetry§ at the age of 4 months when lying on his stomach. His right arm always was caught under his chest, and fifty-fifty when engaged in reaching for an object with the other arm, he still did not use his right arm. Throughout his showtime twelvemonth, this asymmetry persisted, causing the child to fall to his correct side when lying on his tummy, or when sitting, and fifty-fifty when he started to walk.
Righting from Supine to Prone.
Rolling over from back to tummy usually begins around 3 months of age. It involves a rotation around the longitudinal axis of the body (see Fig. eleven), in a corkscrew mode, one body segment later on the next. Typically, in the primeval grade of such righting, the pelvis turns first, then the torso, and finally the shoulders and caput. By 6 months of age, cephalic dominance is axiomatic (ten, 11), and this social club is reversed. The head turns first, and the shoulders, trunk, and pelvis follow (Fig. 1).
A normal infant, ≈half-dozen months one-time, shows cephalic say-so in the initiation of righting to prone when lying supine on the ground. The head turns first, and the shoulders, torso, and pelvis follow sequentially until the child reaches the prone position.
A definition of the three types of motility that tin be performed by the body. (Plane movement) The limb segment moves in a plane that is at 90 degrees to the centrality of its movement. (Rotatory motility) The limb moves at an bending of nil degrees to its own axis: i.east., it does non movement in space, but merely twists effectually the axis through its length. (Conical move) The limb moves at an angle <90 degrees and >0 degrees to its axis of motion.
In our experience, impairments in righting exist in autistic infants. Some cannot plough over at all. Others, although managing to turn over, and thus "getting the task done," exercise it in the following manner: starting from lying on their side (rather than on their back every bit normal children would do), they arch themselves sideways past raising the head and pelvis upward (Fig. 2). This narrows the base of the trunk and so that by moving the upper leg forward that leg tin can serve as a weight to topple the body over. All of the segments of the torso move en bloc, non in a corkscrew fashion. This results in the child falling over, without whatsoever agile rotation.
An autistic babe, ≈5 months old, cannot right by rotation. Instead, he arches the caput and pelvis sideways upwardly, moves the acme leg forward, and topples over en bloc, without the sequential segmental rotation in the righting motility characteristic of normal children.
It must be noted that, even though we have videos of 17 autistic children and then far, simply a few of these home videos really filmed righting on the footing in such children. Thus, we accept but a very limited sample (n = 3) of the righting behavior of autistic infants. However, the sideways–upwards pattern of righting seen in all three of these autistic children is quite different from what normal children ever bear witness when righting on the ground. The abnormal design of righting that nosotros have just described was seen by us when the autistic children ranged in age from 6 to 9 months one-time. I of these children, at the age of 3 months, when lying supine, flexed his head and neck strongly forward in the midline (see Fig. 3 a and b). Such midline forward flexion tin be seen in the normal newborn at the age of 5 days (ix), just it is atypical for it to appear at 3 months of age. In other words, the forward-flexion pattern shown by the autistic child may exist a more infantile pattern.
An autistic child, ≈3 months erstwhile, lacking the ability to rotate around the torso midline during righting (a), attempts to sit upward past ventroflexing his body in the midline plane (b).
Sitting.
Usually, at ≈6 months of age, a normal baby can sit upright. He maintains his equilibrium past distributing his body weight equally on his sitting bones, even when, past reaching for a toy, his upper torso volition be out of the vertical. Turning his head, rocking in place, or busying his hands with objects, he maintains his stability.
Some autistic children were not able to maintain sitting stability at this age. In the farthermost, he or she simply savage over similar a log, without using any allied reflexes to protect himself (see Fig. four). In other cases, where there was less severe motility disturbance, the baby managed to sit down for a few minutes at a time, simply, because his weight often was non distributed equally on both sides, his posture was asymmetrical, leaning to ane side, and he fell over when reaching for objects or moving his arms and upper body.
An autistic daughter, viii.5 months sometime, shows no allied protective reflexes when falling (e.g., extending the artillery and hands out to protect herself from striking her caput when falling toward the ground).
Crawling on Easily and Knees.
Nigh babies start to crawl at about the same time they begin to sit. There are several forms of creeping and crawling and at that place is much debate about the interlimb patterning involved (see ref. 12 for a detailed give-and-take of this topic). We will consider here just crawling on hands and knees. The following will exist used every bit a reference starting position: arms vertical at shoulder width, palms on the floor fingers pointing frontwards; thighs vertical and hip-width autonomously, knees on the basis with lower legs and feet resting on the flooring pointing backwards; and weight equally distributed on all four limbs (encounter Fig. five). Annotation that this is an "ideal" position: a babe who is playing and moving around rarely will stop in this position, but it can serve as a reference relative to which other movement patterns—normal and abnormal—can be studied. When crawling forward on hands and knees, the arms and thighs motility parallel to the midline centrality of the body. That means that the artillery stay shoulder-width apart, then do the thighs.
A normal baby, ≈6 months old, shows good support in the arms and legs while itch forward.
Autistic Children May Testify Deviations from the Normal Pattern of Itch.
Asymmetrical lack of adequate support in the arms. As shown in Fig. half-dozen, this infant did not have acceptable support in his arms, and then that he supported himself on his forearms rather than his easily. Annotation that ane arm is crossed in front of the other so that his base of support on his arms is very narrow. Although back up was scarce in both arms, the right arm was weaker than the left, so that reaching was washed with the left arm while the correct arm often was defenseless under the body. He appeared to intend to crawl forward to attain the small roller on the floor in forepart of him. Because he could not move his thighs toward his stomach, and thus was non able to "step" forward on his knees and shift his weight, he was stuck in place. The result was that he raised his pelvis into the air while leaning on his upper arms, his body in an upside downwardly 5 shape. He tried a few times to move forward by bringing his knees to the footing and pushing himself, simply again and over again, instead of moving forward, his knees came off the flooring, extending his legs and bringing his bottom up.
An autistic baby, ≈5 months erstwhile, is unable to support himself on his hands and is unable to bring his knees toward his breast to crawl forrard, so he lifts his rump up while trying to clamber just cannot movement forward from the spot.
Asymmetry in the legs.
(i) In the next video taken of the child described in a higher place, at the historic period of 6 months, the artillery had developed back up, and the legs at present could be used in itch. However, a remainder right-sided deficiency remained in the apply of his legs in crawling: from the starting position described above, the left leg moved the usual way (thigh moves forward under the belly, lower leg and foot sliding on the floor) whereas the correct thigh did not move actively. It was carried passively past a sideways flexion of the correct hip (so that the hip came closer to the rib cage). This motion of the hip carried the thigh medially also as forrard, so that, with each crawling step, the base of the body progressively was narrowed, resulting in eventual falling over to the correct.
(ii) Another autistic child is shown in Fig. 7. When this baby crawled, the left leg moved the usual mode (the left thigh moved forward under the abdomen with the lower leg and pes sliding on the floor, and the left knee contacted the ground at the finish of each step) whereas the right leg stepped forward by using the human foot (the lower leg is vertical with simply the foot contacting the ground at the end of each step).
An autistic baby shows disproportion in his crawling: the left leg crawls properly, but the right foot steps rather than crawls.
Standing.
A normal baby, ≈8–10 months onetime, may pull himself up and correspond a few minutes, sometimes leaning against a piece of heavy furniture. After a short period of fourth dimension, though, he typically will subside to the floor to keep his activities. One autistic girl of that age seen in Fig. viii stood in i place leaning her back against a heavy slice of article of furniture for periods as long every bit 15 minutes at a time. Such relative akinesia may signal abnormality.
Moebius Syndrome shape of the mouth in an 8.5-month-old autistic girl. The lower lip is flat, but the upper lip is biconvex in a characteristic shape.
Walking.
When a babe starts to walk, his gait develops through fixed stages that incorporate a proximal–distal slope that governs the control of the unlike segments of the legs. The thigh, the segment of the leg near proximal to the body, is the but segment that actively moves at beginning. The lower leg and the foot simply are carried passively along past the movement of the thigh. They practice non motion actively. Later, they add their action successively. This paradigm of normal walking enables us to analyze deviations from it.
When a infant starts to walk, three stages tin can be differentiated. (i) Waddling: From a starting position of stability (run into Fig. 9), in which the babe stands still, both legs parallel and weight equally distributed, the trunk weight is shifted laterally to one leg. This enables the other leg to lift and stride forward. Considering but the thigh moves actively (as in crawling, the lower leg and foot are existence carried passively forth), the step is very short. The foot is planted as a whole, neither toes nor heel touching the flooring first. The baby then shifts his weight sideways to the leg that has just stepped, releases the other leg and brings it in a "grab-upwards" step to a position parallel to the leg that but had stepped. The result is a "waddling walk" in which, although the baby progresses forrad, he does it past waddling from side to side, with long intervals of standing still between each pair of steps. (This can exist noticed almost clearly past watching the head.) The hands are raised shoulder loftier, forearms vertical (See Fig. 9).
A normal babe, ≈ten months old, holds his artillery upwardly at shoulder level as he is just get-go to learn to walk.
(2) Intermediate stage: First the step-gesture, then the shift of weight; the catch-up step is transformed into a full stride frontwards and the step cycle develops as follows. The torso weight shifts, allowing the babe to release the rear human foot from the ground by rolling it from heel to toe, which, in turn, flexes the lower leg relative to the thigh. When, from this position, the lower leg swings forward, carried by the movement of the thigh, the whole leg is lowered back to the ground, the foot landing flat alee of the other foot. Simply later on the leading foot has been placed on the floor is the body weight shifted forrard (rather than from side-to-side as in stage i). The artillery are lowered so that the upper artillery hang downwardly along the sides of the body, and the lower arms are held waist-loftier, parallel to the footing, pointing forwards. It should exist noted that, in adults with Parkinson's affliction, there is a stage of deterioration of the step bicycle that parallels the form of stepping shown in this intermediate stage of the normal development of walking. Only after the leading foot is on the footing does the body weight shift frontward (xiii).
(iii) Final stage: The body weight is superimposed on the step gesture; although in stages i and ii, the shift in body weight was delayed until both anxiety were on the ground, in this stage, weight shift occurs simultaneously with the stepping motility of the leading leg (while the leading leg is in the air). The leading foot then touches the floor heel showtime, and, as the rest of the foot rolls onto the flooring, it acts to wheel the body weight smoothly forrard. The rear heel lifts from the ground earlier the front end foot touches the basis, enabling one to come across that the weight is being shifted. The whole cycle is permitted by and permits the continuous shift of weight forwards. The rolling of the foot determines the flexing of the lower leg, which then swings forrad and extends to bring the heel of the flexed foot in touch with the floor. The arms are downwardly along the sides of the torso, non coordinated even so with the footstep cycle.
These three stages in the development of the stride tin can be observed in every baby that starts to walk. However, the duration of each stage may vary greatly, lasting anywhere from a few days to several weeks. Likewise, the command of the arms may develop at different rates from that of the legs. For case, the arms may exist in an advanced stage (down aslope the body), and the legs may be in stage i or 2, and vice versa.
In the gait of autistic children, the deviations from the normal can be categorized every bit follows. (i) Asymmetry: In normal walking, the movements involving the arms and legs are symmetrical. In every autistic kid nosotros have seen so far, some degree of asymmetry has been found. For example, when walking, a ten-year-old girl held the right arm in a more infantile position (lower arm held at waist pinnacle, every bit described above) while the left arm was held downward as information technology swung alongside the body. When walking, a 3-year-old male child exhibited an infantile pattern in the right leg, where but the thigh was moving, carrying the lower leg and the foot with it. The other leg showed a more mature pattern; that is, all parts of the leg moved relative to one some other, the heel of the foot beingness placed on the ground kickoff.
(2) Delayed evolution: At the age of 2 or fifty-fifty after, the gait may be more infantile than normal. Thus, one autistic child at the age of 2 exhibited active movement of each thigh but, with the lower leg and pes being carried passively. Besides, the foot was planted on the floor as a whole, and there was no release of the hind heel and thus no polish transfer of weight.
(iii) Sequencing, not superimposition: At the age of 5, equally shown in Fig. 10, this autistic child exhibited all of the components of a "mature" step; that is, the thigh and lower leg and foot moved actively forrard, but this was done without the shift of weight that usually goes with information technology. Simply afterwards the leg was extended fully in the air did the shift of weight occur, so that the kid fell forwards on to it in a "goose step" course of walking. The shift of body weight occurred after, not along with, the motility of the leg.
(a) A 5-year-old autistic male child has a fully developed step gesture. All 3 segments of the leg move actively (run into text), but his torso weight does not shift at the same fourth dimension, resulting in a class of goose-pace. (b) The body weight simply and then is shifted and so that the boy falls on to the outstretched leg at each step. This is a form of sequencing rather than superimposition of ane movement on the other.
(iv) The arms: In our experience, as a general rule, papers written about walking deal simply with the activeness of the legs, omitting any discussion of the part of the arms in walking. This is unfortunate, considering the action of the arms is extremely important in facilitating the gait via allied reflexes. In earlier work (13), it was shown that patients with Parkinson's disease can greatly augment the size and speed of their steps by increasing the amplitude of their arm swing. Furthermore, as described above, there are specific positions of the arms that accompany the stages of development of walking. These arm positions tin serve every bit milestones along the course of normal development. If, in the grade of development, there is abort in an early stage (every bit signaled by the position of the arms), this can point abnormality. For instance, in the study carried out by Vilensky, Damasio, and Maurer (iii), several autistic children (ages 3–10) exhibited more infantile positions of the arms while walking: the forearm frequently was held parallel to the ground, pointing forward. In several cases, the arms were not held in a symmetrical position: one arm was in a more than mature position (the arm fully extended downwards alongside the torso) while the other was in a more infantile position (forearm held horizontal, pointing forrad).
(5) Arm-and-mitt flapping: Arm-and-hand flapping oft can be seen in autistic children. It too can appear in normal children, usually for a few months, before it disappears. For this reason, it is difficult to use as a sign diagnostic of autism. Notwithstanding, if it persists to an age at which the mature grade of walking should be well adult (ii years former or more than), then other confirming signs should be looked for as well.
In some of the children studied hither, we observed a characteristic oral cavity shape (see Fig. viii) called "Moebius Syndrome" (14). This mouth shape tin exist seen in the first few days after birth and may persist throughout infancy and on into adulthood. It does not occur in all infants who turn out to exist autistic, but, when information technology does occur, information technology signals the demand to discover closely the movements displayed by the infant. If some of the other symptoms of motion disorder that we accept described here also occur, it strengthens the possibility that autism is involved.
DISCUSSION
Autism more often than not is diagnosed at ≈3 years of age, when a kid begins to participate in organized social settings (in a nursery school, for example). Because social skills required are aberrant in such a kid, it is relatively easy to spot autistic behavior there. Such a kid may non participate in social play with other children, stays by himself, and does not want to be touched by anyone. He refrains from eye contact, has difficulty expressing himself verbally, and sometimes does non talk at all. Indeed, Osterling and Dawson (15) were able to describe the deviant behaviors of autistic children past analyzing their social beliefs from videos taken at their first birthday party. The trouble is that, in infancy (four–6 months), the social symptoms are non so readily apparent. The infant in his crib relates largely to himself, and but his movements reflect the action of his nervous system. The child's mother is ordinarily aware very early that something is incorrect, just, because she is unable to specify something diagnostic, the pediatrician she consults often tends to reassure her that this is a minor trouble that the child volition abound out of. Hashimoto et al. (xvi), using developmental filibuster, poor facial expression, and failure to make eye contact every bit indicators, were able to screen for autism at 6 months. Considering information technology has been shown that virtually all autistic children at after ages have movement abnormalities (ii, three), nosotros reasoned that such abnormalities might be axiomatic in the first few months of life. Every bit shown in the present paper, this is indeed so.
It is important that the abnormalities in move that we have described hither can be seen very early on in infancy, long before the behaviors in social settings that currently grade the footing for the diagnosis of autism. Diagnosis in infancy can signal the demand for therapeutic behavioral interventions that might provide greater degrees of recovery from autism. Temple Grandin (17) is a famous case of the remarkable degree of spontaneous recovery that is possible in autism. It is evident that the earlier the therapy, the more effective it will be. Therefore, the fact that abnormalities in movement can be very early on indicators of potential autism is important to know.
It also should exist noted that the motility disturbances that we have found in autistic children typically occurred on the correct side of the torso. This is in contrast to the movement disturbances reported in schizophrenic children in infancy, where they occur typically on the left side of the body (18). A more detailed comparing of the motion disorders found in autistic infants with those plant in schizophrenic infants would be very valuable.
The nowadays findings are likewise important for pediatricians. Time and time again, in our correspondence with the mothers of autistic children, we accept heard that the mother suspected that something was wrong with her infant but that the pediatrician told her that everything was all right and that she demand not worry. The pediatrician should be the primeval, non the concluding, to know that the child might be autistic. An sensation that elementary movements such every bit those described in the present newspaper might assistance in the diagnosis of potential autism would be valuable for pediatricians.
The fact that such early diagnosis is possible now highlights the need for the evolution of before therapies that will be effective in the handling of potentially autistic children. Because diagnosis was not generally possible and so early, no systematic methods are currently bachelor for the treatment of infants at chance for autism. Our findings should provide the impetus for systematic search for such treatment methods.
How exercise we reconcile our findings of deficits in the development of movement in autistic infants with the reports from parents cited past Rimland (1) indicating that many autistic children display hyperagility and hyperdexterity? Two possibilities exist. First, it is possible that, in our express sample of autistics, nosotros have not achieved an adequate sample and that in that location exists a subgroup of autistics that display such hyperagility and dexterity even in infancy. Because we obtained our videos without asking for whatever special characteristics other than a diagnosis of autism, we have no reason to presume that at that place was a systematic bias in our sample. Alternatively, it is possible that a transformation occurs in development in autistic children, and so that many of the children whose videos showed motility abnormalities in infancy might at a later historic period prove hyperagility and dexterity, akin to that reported by Rimland (1). This merits farther investigation.
Finally, in infancy, the motion disorders nowadays in autism are clearest, not yet masked by other mechanisms that have adult to compensate for them. Information technology is possible that they may vary according to the areas of the brain in which developmental delay or harm has occurred. For instance, Kemper and Bauman (6) have pointed out from anatomical analysis of the brains of autistic individuals that the limbic organisation likewise as the cerebellum may show small shrunken cells. Courchesne (4) has prove from MRI analysis that the cerebellum may evidence hypoplasia or even hyperplasia in certain regions of the cerebellum. By combining movement analysis in infancy with MRI analysis, information technology may be possible somewhen to diagnose differential areas of brain interest in unlike subtypes of autism.
Annotation. Unfortunately, we did not have electronic versions of the figures used in this paper. We attempted to increment the clarity of the figures (which were taken direct from home videos) with numerous methods, but, because of the nature of the original images, we had little success.
Acknowledgments
We are grateful to the families who sent united states the videotape fabric that we have analyzed in this paper. Their goodwill and cooperation fabricated this work possible.
Footnotes
§Asymmetry can be seen briefly in many normal babies. However, if such asymmetry is persistent, a closer test would be worthwhile.
References
i. Rimland B. Autism Res Rev Int. 1993;7:three. [Google Scholar]
2. Damasio A R, Maurer R Yard. Arch Neurol. 1978;35:777–786. [PubMed] [Google Scholar]
iii. Vilensky J A, Damasio A R, Maurer R G. Arch Neurol. 1981;38:646–649. [PubMed] [Google Scholar]
4. Courchesne East, Saitoh O, Yeung-Courchesne R, Press M A, Lincoln A J, Haas R H, Schreibman L. Am J Roentgenol. 1994;162:123–130. [PubMed] [Google Scholar]
5. Piven J, Saliba K, Bailey J, Arndt Due south. Neurology. 1997;49:546–551. [PubMed] [Google Scholar]
6. Kemper T L, Bauman M L. In: Neurologic Clinics: Behavioral Neurology. Brumback R A, editor. Philadelphia: Saunders; 1993. pp. 175–187. [PubMed] [Google Scholar]
7. Waterhouse L, Fein D, Modahl C. Psychol Rev. 1996;103:457–489. [PubMed] [Google Scholar]
eight. Eshkol N, Wachman A. Movement Notation. London: Weidenfeld and Nicolson; 1958. [Google Scholar]
9. Casaer P. Postural Behavior in Newborn Infants. London: William Heinemann Medical Books; 1979. [Google Scholar]
11. Pellis South M, Pellis V C, Chen Y-c, Barczi S, Teitelbaum P. Behav Encephalon Res. 1989;35:241–251. [PubMed] [Google Scholar]
12. Freedland R L, Bertenthal B I. Psychol Sci. 1994;v:26–32. [Google Scholar]
thirteen. Teitelbaum P, Maurer R Thousand, Fryman J, Teitelbaum O B, Vilensky J, Creedon M P. In: Stereotyped Movements: Brain and Beliefs Relationships. Sprague R L, Newell Chiliad 1000, editors. Washington, DC: Am. Psychol. Assoc.; 1996. pp. 167–193. [Google Scholar]
14. Gillberg C, Coleman Thou. The Biological science of the Autistic Syndromes. Oxford: MacKeith; 1992. [Google Scholar]
fifteen. Osterling J, Dawson G. J Autism Dev Disord. 1994;24:247–257. [PubMed] [Google Scholar]
16. Hashimoto T, Tayama M, Murakawa K, Yoshimoto T, Miyazaki G, Harada M, Kuroda Y. J Autism Dev Disord. 1995;25:i–17. [PubMed] [Google Scholar]
17. Grandin T, Scariano 1000. Emergence: Labelled Autistic. Navato, CA: Arena; 1986. [Google Scholar]
18. Walker Due east F, Savoie T, Davis D. Schizophr Bull. 1994;20:441–451. [PubMed] [Google Scholar]
Why Do Babies Move Arms and Legs So Much
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC25000/