ENVIRONMENTAL FACTORS AFFECTING HUMAN DEVELOPMENT, BEFORE AND AFTER BIRTH

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ENVIRONMENTALFACTORSAFFECTINGHUMAN

DEVELOPMENT,BEFOREAND AFTER BIRTH

Hilda Knobloch, M.D., and Benjamin Pasamanick, M.D.

Clinic of Chili! Development, the Children's Hospit2l, Columbus, Ohio (H.K.), and the Departments of Pediatrics and Psychiatry (H.K., B.P.), Ohio State University College of Medicine

P REVIOUS INVESTIGATORS preoccupied with

the nature-nurture controversy have concerned themselves with â€œ¿provingâ€•that one or the other of these influences is most vital in moulding human development.1 In vestigation and assessment of exogenous factors in development are not a matter of â€œ¿either-orâ€•but rather one of attempting to assign proper roles to each influence.

What makes man different from lower

animals is obviously his distinctive genetic constitution, and this is the fundamental basis on which all human behavior rests. Because this is so obvious, some people

have made genetic endowment the cause

of all human variation. In the process they have set up a â€œ¿strawmanâ€•and workers in this area must needlessly spend time in knocking him down. In attempting to ex plain what does cause human variation the

analogy with physical growth has been

drawn upon, perhaps too freely. In the first place, physical growth characteristics ap pear to be normally distributed, and it has consequently been hypothesized that psy chologic functioning must therefore be sim ilarly distributed. In fact our instruments

formeasurement have been constructedto

coincide with this notion. Secondly, be cause there was a relationship between the physical growth characteristics of the child and his parents which has been attributed to genetic factors, the same genetic model has been used for psychologic characteris tics; this model may not hold for psycho logic functioning.

There is now, in fact, considerable evi dence that physical growth characteristics are environmentally influenced. For exam

pie, Boas2 demonstrated the increase in height of the children of immigrants over their parents and showed that skull shape, previously considered an ethnic character istic, changed in different groups from one generation to the next. The marked physi cal differences between Japanese born in Japan, Hawaii and the United States are well known, and countless other examples could be adduced.

Since human development is affected by so many different modes of integration, with the social forces frequently influenc ing the psychologic behavior by way of the biologic functions, any attempt to unravel them must involve an understanding of the various factors influencing behavior as early in life as they can be studied and analyzed. From our studies it seems that a new approach to the problem of the de velopment of neuropsychologic function ing should be sought. There does not ap pear to be very great variation in beha vioral functioning during infancy; in this period the social factors seem to be operat ing on neuropsychologic function largely through the biologic level of integration, and a good deal of what variation does oc cur can be explained by damage to the cen tral nervous system. However, as the in fant grows, the sociocultural level of in tegration appears to have a more direct relationship to psychologic function, with most of the variation in the period beyond infancy explainable on the basis of differ ences in social experience.

These relationships of socioeconomic var iables to neuropsychologic integrity be

came apparent in the course of a series of

ADDRESS:(ilK.) Clinic of Child Development, 561 South 17th Street, Children's Hospital, Columbus 5, Ohio.

PEDIATHICS, August 1980

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time to measure the differential risks of de veloping the conditions one is seeking to investigate.

METHOD OF STUDY

The data on which the major portion of this report is based were collected in the course of a study of 500 premature infants and 492 full-term matched controls, conducted in Balti

more, Maryland, since 1952. Details of sample selection and the procedures have been fully reported;6 only a few matters germane to the

present discussion will be repeated. The in fants were seen at approximately 40 weeks of age and an evaluation of neurologic status and a prediction of intellectual potential were made on the basis of a Gesell Developmental Examination.7 This examination was done by a pediatrician trained in its use, who in most instances did not know at the time of the evaluation whether the infant was premature or full-term. Three-fourths of the infants were

examined between the ages of 39 and 41

weeks, and in the case of the premature in fants the chronologic age was corrected for the estimated amount of prematurity.

RESULTS

One of the important findings of the study, that the amount of neurologic and intellectual damage increases as the birth

weight decreases, has already been re

ported in detail.6 Table I summarizes the developmental quotients for the total pre mature and the full-term control groups in the five major fields of behavior. In the control infants there are no significant dif ferences between whites and non-whites, the respective developmental quotients in the various fields of behavior being as fol lows: general development (adaptive be havior), 105.4 and 104.5; gross motor be havior, 114.7 and 113.4; fine motor behav ior, 97.6 and 99.2; language behavior, 102.5 and 102.9; personal-social behavior, 108.6 and 106.5. In the premature group there are apparent differences in favor of the white infants. There is, however, a larger percentage of babies with low birth weight in the Negro premature group, and when an adjustment is made for variations in weight distribution, the disparity between retrospective epidemiologic investigations

in which we were engaged. On the basis of a hypothesis of a continuum of reproduc tive casualty, with a lethal component of cerebral damage giving rise to fetal or neo natal death, and a sublethal component resulting in various degrees of disability, a series of neuropsychiatric disorders was in vestigated.' These ranged from the more obvious conditions of cerebral palsy and mental deficiency through lesser handicaps, such as behavior disorders, reading disabil ities and tics.

All of these studies demonstrated an as sociation between the presence of compli cations of pregnancy, particularly vaginal bleeding in the third trimester, toxemia and prematurity, and the development of neuropsychiatric disorder. The incidence of

these complications was higher in the

mothers of the affected individuals than in the mothers of the controls. It had already been demonstrated4 that the high rate of prematurity in the non-white population was probably not an innate racial charac

teristic, but in part, a portion of a socio

economic continuum; the rates for the white upper-economic group, white lower-eco nomic group, and non-white group being 5.0, 7.6, and 11.4% of births, respectively.

Similarly, investigation of the control popu lations for these retrospective studies,' con sisting of children not known to have neu ropsychiatric disability, showed that the

important complications of pregnancy

(bleeding and toxemia) increased as the so cioeconomic status decreased, being 5% in the white upper-economic fifth, 10% in the lower-economic fifth, and 15% in the non white group. Comparable rates for total complications, which also included those not specifically related to pregnancy, were 5, 15, and 50%, respectively.

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Weight

GroupPrematvres4ControlsRaceWhiteNon

whiteWhiteNon whiteNo.

of

Cases(212)(289)(223)(269)General

(Adaptive)104.0100.8105.4104.5Gross motor109.9104.1114.7113.4Fine

motor95.492.697.699.2Language101.998.7102.5102.9Personal-social108.1103.8108.6106.5

212 HUMAN DEVELOPMENT

shown, a further examination of intra-group

distinctions might be of interest. The white infants were divided into three economic groups (the lowest two-fifths, the middle fifth, and the highest two-fifths) on the basis of area of residence as designated by

census tract. The Negro group was con

sidered in its entirety, since census-tract designation does not make the same distinc tions within the non-white as within the white group. There are no significant dif

ferences and no trend between the eco

nomic fifths, for either prematures or con trols, in any field of behavior.

Education of the parents is known to correlate highly with other indices of status, such as occupation, and, while obviously closely related to the census-tract rating, it may be a more sensitive index of socio economic status because census tracts are

only crudely homogeneous. When the in

fants are divided on the basis of the edu cation of the mother, significant differences are found only in gross motor behavior, ex cept for the white full-term controls where no significant differences are found in any field of behavior. In the Negro controls the gross motor quotient is lower if the mother had less than an eighth-grade school edu cation. In the white prematures this same

quotient is higher if the mother had a

twelfth-grade education or more, while in the Negro prematures the trend is in this

same direction, but too few of the Negro

mothers had graduated from high school for the differences to be statistically signifi cant.

The findings so far have concerned them selves with developmental quotients which summarize in a single score the behavior of the infants in a variety of behavior pat terns. Perhaps comparisons on these indi vidual items might reveal differences hid den by a clinical summary in the form of a quotient. The frequency distributions of

positive and negative responses in 54 adap

tive behavior patterns were analyzed and

comparisons made by race and birth

weight. As expected, a higher percentage of full-term control infants had more ad

TABLE I

DEVEI,OI'MENTAL QUOTIENTS AT 40 WEEKS OF AGE,

BY BIUTH WEIGHT AND RACE

Baltimore, Maryland, 1952â€”1953

Developmental Quotients

*Not adjusted for distribution by birth weight.

the two premature groups disappears. The developmental quotients in the premature group are lower than in the corresponding full-term control group in all fields of be havior. Unadjusted for differences in distri bution by birth weight, these figures are, for white and non-white infants, respec tively: general development (adaptive be havior), 104.0 and 100.8; gross motor be havior, 109.9 and 104.1; fine motor be havior, 95.4 and 92.6; language behavior, 101.9 and 98.7; personal-social behavior, 108.1 and 103.8. The apparent greater dif ference between the premature and control infants in the non-white group is also ex plained by the excessive representation of infants with low birth weight in the Negro group.

Fine-motor and language-behavior quo tients in the full-term infants do not differ significantly from the norms given by Ce sell and Amatruda,@ while in the other areas of development there is some acceleration in development over the normative infants.

There is, of course, a sharp socioeco nomic distinction between the white and Negro populations in Baltimore which is probably greater than any intra-group dif ferences which can be demonstrated. Al though no significant differences from this

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RaceWhiteNonwhiteMeanS.D.MeanS.D.Physical

StatusBelow median weightat

birthand 40

weeks106.612.3104.113.5Above

median

weightatbirthand40weeks105.97.6108.98.3

vanced behavior than did the premature infants. When an adjustment is made for the birth-weight distribution in the popu lation, the percentage of positive responses is not changed by more than 1 in any of the items for either of the races. When the white and non-white infants are compared, significant differences between them are

found in only two items which are very

closely related. A significantly higher per centage of the Negro infants â€œ¿hitthe cube against the cupâ€• or â€œ¿thrustthe cube into the cup without releaseâ€• than did the white

infants. When so many comparisons are

made, one can expect to find significant differences this frequently by sampling va riation alone.

Since this analysis also appears unpro ductive of racial differences, we may turn to factors which reflect nutritional and physical status. We had shown in previous studies8'9 that weight at birth and later growth were the only ones in a series of factors which influenced the adaptive de velopmental quotients in a group of in fants. The full-term control infants in the Baltimore premature study were therefore divided into two groups on the basis of

whether they were above or below the

race- and sex-specific median weight at the time of birth as well as at the time of the

40-week examination. The findings pre

sented in Table II indicate that there is no significant difference in the mean adaptive developmental quotient in the white in fants; that for the infants below the median at both times being 106.6, while that for the infants above the median weight at both examinations is 105.9. In the Negro infants, however, those infants below the median weight at the time of birth and also at the time of the 40-week examination have an average developmental quotient of 104.1, which is significantly lower than the quoti ent of 108.9 found in those infants above the median weight at both examinations. This difference is too small to be of practical im portance, but does indicate that these fac tors do influence adaptive behavior.

It would be well at this point to shift

TABLE II

GENERAL (ADAVFIvE) DEVELOPMENTAL QUOTIENTS OF FULL-TERM CONTROL INFANTS BY PHYSICAL

STATUS AT BIRTH AND AT THE 40-WEEK

EXAMINATION, BY RACE

Developmental Quotients

from the comparison of groups and focus attention on the distribution of the gen eral developmental quotients in an infant population. Because of differences in inci

dence and mortality between the birth

weight and racial groups, the distribution of the general developmental quotients was adjusted to correspond to the composition of a surviving infant group. The details of

this procedure have already been pub

lished'Â° and it is this adjusted distribution of intellectual potential that we wish to dis cuss at present.

The intellectual potential is a clinical estimate of intelligence based largely on the adaptive maturational status of the child. It takes into account not only the de velopmental level but also the quality of the behavior, and is expressed in the ter minology usually used in placing a child within or outside the average group, which

ranges from defective to superior. Concep

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214 HUMAN DEVELOPMENT

tal quotientâ€• and â€œ¿adaptivebehavior quo tientâ€• interchangeably, and while they are not completely identical, the correlation between them is high (.97 for the white control infants, for example). Although on the average the general developmental quo tient was less than one point higher than the adaptive, the former takes more ac count of the clinical factors already men tioned.

We must make quite clear at this point that motor behavior is not a determinant of intellectual functioning, but rather of neu

rologic integrity. Acceleration in gross mo tor behavior is not a reason for giving a better prognosis for the future. On the other hand, retardation because of defects in neural integration is of the utmost clini cal importance in distinguishing lowered adaptive potential from distortions in be havior resulting from abnormal neurologic states. Cognizance must, of course, be taken of the hazards of separating developmental quotients from the other factors of clinical judgment, but it is a necessary step if one wishes to make comparisons with the find ings at later ages and point up the impli

cations of the data obtained in infancy. Analysis of the distribution of the gen eral developmental quotients indicates that there are no significant differences between the white and non-white infants when an adjustment for the distribution of birth weights is made. The most striking find ing, however, is that the distribution curve differs sharply from the distributions for older children11'12 reported in the litera ture. The first important difference is that only 1.5% of the infant population has gen eral developmental quotients below 80, and 2.7% below 90. Secondly, there is a sharp rise starting at this point so that more than 90% of the infant population has develop mental quotients between 90 and 120.

DISCUSSION

The findings of the retrospective studies on the effects of socioeconomic factors in pregnancy and those of the anterospective study of premature infants mutually sup

port each other. Prenatal experience, birth weight and later physical status are the most important, and, in essence, the only significant factors we have been able to discover at this point that result in group differences in developmental quotients. Whatever other internal variations were found in the groups are explainable by the fact of increased damage in the lower so cioeconomic groups, where a greater num ber of babies with low birth weights are found. This decreased weight is evident not only in an increased incidence of pre mature births, but also in a lower average birth weight.

These arguments can only hold if what is measured in infancy is related to later behavior.It is a truism to statethat the central nervous system from which behav ior stems in infancy is the same nervous system which continues to operate through out the life span. Infant behavior is not the same as socially-learned responses, but socially-learned behavior is also rooted in the central nervous system. It would seem apparent, then, that adequate behavioral measures of the integrity of the central nervous system during infancy should re veal a continuum with later functioning, particularly in those patterns which can be related to injury.

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ARTICLES for the failure of all observers to find them. Either the methods being used were inade quate, or they were not employed properly. We will undertake to review the recent evidence which indicates that, contrary to these previous reports, when an adequate infant-examination is used as a clinical neu rologic method by a physician trained in its use, it is as effective a predictor as any psychologic examinations done at 3 to 7-year intervals.

There are four major groups of infants

with whom the Gesell Developmental Ex

amination was used in the first year of life and correlations made with later examina tions. The group which was smallest in size, but not necessarily in importance, con sisted of 50 Negro infants from New Haven who were re-examined at 7 years of age by examiners unaware of the initial findings.14 The correlation between the first examina tion and that at 7 years was .5. The second was a group of approximately 100 infants examined at several ages between 16 weeks and 18 months. The correlations ranged be tween .5 and .75, but in this group the general behavior at previous examinations was recalled by the examiner in most in stances. The third consisted of several groups of infants who were examined prior to adoption placement at Yale's Clinic of

Child Development in New Haven and

were re-examined at 5 and 9 years of age. In one of these groups of infants who were

recommended for adoption placement be

cause they were found to be free of neuro logic or intellectual deficit, a correlation of .55 was found when the infants were re examined at 5 years.1' The results have al ready been publishedo also for the fourth and largest group comprised of approxi mately 300 of the 1,000 infants already de scribed in this paper. When they were re examined at 3 years of age a correlation of .5 was found for the total group. When neurologic or intellectual impairment was present the correlation rose to .75.

In considering these correlations, the question of bias on the part of the exami ner could be raised, because in the second

and fourth groups the same examiner did both examinations. It could be argued that there was a vested interest in the results of intra-group comparisons as well as in the correlation with later examinations. In view of our support of the theory that Negro white differences can be explained by en vironmental factors, for instance, it could be argued that we were systematically up grading the performance of the Negro in fants. Extensive discussion of this matter of bias is not possible at the present time, but conscious or subconscious favoring of the Negro infants is not sufficient to explain the lack of differences between the white and non-whites, or the correlation between the two examinations. Consistent and expected differences between the premature and the control infants were found at both times and the examiner had no knowledge of the birth weight at either examination.

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HUMAN DEVELOPMENT 216

PERCENT

OF CASES

45

FIG. 1. Distribution of intelligence quotients reported in the literature compared to distribution of general developmental quotients in Baltimore

study of an infant population (1952).

40

35

30

20

IS

10

.â€”.-. BALTIMORE INFANTS .â€”â€”. MACMEEKEN (SCOTLAND) .---@ STANFORDâ€”BINET REVISION

75 25 35 45 155 165 175

44 54 64 74 84 94 04 114 124 34 44 154 64 174 184

QUOTIENT

nated as familial mental defectives, but also in the 75 to 90 group which is considered to be at the lower end of the normal scale because of inferior hereditary endowment.

It might be argued that the increase in spread in developmental quotients with ad vancing age can be explained by the in adequacy of the infant examination, but this is not tenable in view of the correla tions found. Since the period between 9 months and 3 years represents one of rela tively rapid development, probably com parable to a 5 to 10-year interval later in life, the correlation found is even more sig nificant. Furthermore, in a large propor tion of the infants with developmental quo tients below 80 a diagnosis of neurologic

abnormality was made. There was a pre

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Age at Examination40YearsRaceWhiteNon Weeks3

whiteWhiteNon whiteNo.

of

(â€˜ases(223)(269)(77)(82)Field

of BehaviorGeneral

(Adaptive)105.4104.5110.997.4Gross motor114.7113.4113.7112.5Fine

motor97.699.2100.798.6Language102.5102.9106.090.1Personal-social108.6106.5110.5106.8

ARTICLES

Infant evaluation is important, therefore, in helping to understand the various factors that mould the development of intellectual functioning. Its usefulness is not confined to its doing what one expects of a clinical neurologic method, namely, identification of the abnormal infant with a below aver age potential, usually on an organic basis, and definition of the nature of his ab normality. We do not necessarily expect to predict the later I.Q. scores precisely, or to identify in infancy the superior school age child who has the benefit of the en riched cultural experiences the tests of school achievement are designed to evalu ate. As a matter of fact, however, the Gesell

Developmental Examination performs as

reasonably in predicting in infancy as other examinations do at later ages. As clinicians we would be satisfied with the following statement: â€œ¿Thisinfant has no neurologic impairment, and his potential is within the normal range; depending on what his life experiences are between now and 6 years of age, he will at that time have an I.Q. by the Stanford-Binet test of above 90, un less qualitative changes in the central nerv ous system are caused by noxious agents, or gross changes in milieu alter major vari ables of function.â€• In actuality the predic t@ons are much more precise than this clini cally acceptable statement. Fifty percent of the 300 infants in the premature study varied less than 10 points, and 75% less than 15 points, between the two examina tions. A host of environmental factors were evident to explain why the correlation was not closer to 1.0 than it is.

We are brought back now a full circle to our opening comments on the nature nurture controversy. While we believe that later behavior is more influenced by learn ing, it is necessary to re-emphasize the truism that there is a fundamental neural structure which underlies the behavior of each individual and that this physiologic organization of the central nervous system is the foundation for all learning.

The findings reported do not deny that man's fundamental structure, and conse

TABLE III

COMPARISON OF DEVELOPMENTAL QUOTIENTS AT 40

WEEKS AND 3 YEARS OF AGE, FULL TERM INFANTS BY RACE

Developmental Quotients

the upper ranges of intelligence quotients. While this is so far a theoretic explana tion for findings at variance with previous reports, an analysis of the 3-year examina tions provides evidence to support this theory of the importance of socio-cultural

factors in later behavior. At 40 weeks of

age, no significant differences in the full term control populations were found be

tween the major socioeconomic groups,

whites and non-whites, and no significant intra-group differences on socioeconomic variables were demonstrated. At 3 years of age the picture is vastly different. Table III indicates that in adaptive and language behavior the white full-term control infants have an increase in their developmental quotients, which rise to 110.9 and 106.0

respectively, while in the non-white chil

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HUMAN DEVELOPMENT 218

quently his basic functioning, is genetically

determined. They merely emphasize the

fact that until the noxious socioeconomic nurtural factors known to affect behavior are removed, the precise role of genetic variation cannot be assessed. Although the evidence is far from complete, the findings of recent studies, our own as well as others, indicate that at present it is reasonable to conclude that, in the absence of organic brain damage, it is life experience and the sociocultural milieu modifying biologic and psychologic functioning which makes the behavior of one individual significantly dif ferent from that of another.

SUMMARY

The relationship of socioeconomic fac tors to pregnancy experience and later neuropsychiatric functioning was investi gated by a series of retrospective and anterospective epidemiologic studies.

The studies demonstrated an increased amount of brain damage in the lower socio economic strata, where a higher incidence of complications of pregnancy and a greater number of babies with low birth weights are found.

In 992 infants examined at 40 weeks of age, pregnancy experience, birth weight and later physical status were the only major factors which could explain group differences in developmental quotients.

The studies further indicated that the relatively small amount of variability found in infancy could be explained largely by

the presence of damage to the central

nervous system, and supported the view that at this period of life social factors af fect the psychologic level of integration

primarily through biologic mechanisms. Later, during the preschool period, the direct influence of the sociocultural forces on the psychologic performance becomes manifest.

REFERENCES

1. Anastasi, A., and Foley, J.: Differential Psychology: Individual and Group Dif

ferences in Behavior. New York, Mac

millan, 1958.

2. Boas, F.: United States Senate Document 208. Washington, D.C., Government Printing Office, 1911.

3. Pasamanick, B., and Knobloch, H.: Race, complications of pregnancy, and neuro psychiatric disorder. Social Problems, 5: 267, 1957-58.

4. Rider, R., Taback, M., and Knobloch, H.: Associations between premature birth and socioeconomic status. Am. J. Pub. Health, 45:1022, 1955.

5. Knobloch, H., Pasamanick, B., and Liien feld, A. M.: Socioeconomic status and

some precursors of neuropsychiatric dis order. Am. J. Orthopsychiat., 26:594,

1956.

6. Knobloch, H., Rider, R., Harper, P., and Pasamanick, B.: Neuropsychiatric Se quelae of prematurity: a longitudinal study. J.A.M.A., 161:581, 1956.

7. Gesell, A., and Amatruda, C.: Develop

mental Diagnosis: Normal and Abnor

mal Child Development. New York,

Hoeber, 1951.

8. Pasamanick, B.: A comparative study of the behavioral development of Negro infants. J. Cenet. Psychol., 59:3, 1946. 9. Knobloch, H., and Pasamanick, B.: Fur

ther observations on the behavioral de velopment of Negro children. J. Cenet. Psychol., 83:137, 1953.

10. Idem: The distribution of intellectual po tential in an infant population, in The Epidemiology of Mental Disorder: A Symposium in Celebration of the Cen tennial of Emil Kraepelin. Washington, D.C., Am. A. Advancement Sc., 1959. 11. Terman, L., and Merrill, M.: Measuring

Intelligence. Boston, Houghton Muffin, 1937.

12. Macmeeken, A.: The Intelligence of a Representative Group of Scottish Chil dren. London, Univ. London Press, 1940.

13. Bayley, N.: Value and limitations of infant testing. Children, 5:129, 1958. 14. Nash, E. H., Nash, H., Pasamanick, B.,

and Knobloch, H.: Further observations on the development of Negro children: status at seven years. Unpublished manuscript.

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1960;26;210

Pediatrics

Hilda Knobloch and Benjamin Pasamanick

BEFORE AND AFTER BIRTH