A Longitudinal Study of Prilnary Reaction Patterns in Children

By ALEXANDER TItOMAS, M.D., STELt,~ CZX'ESS, M.D., HEnnEnr BmcH, PH.D., AND MAncAnET E. IlznTzm, A.B.

G ROWING scicntific attention is being accorded to tile often expressed view of parents, pediatricians and baby-nurses tlmt even in tile neonatal

period and in infancy children are behaviorally distinguishable from one another. -~,7,13,~9,-"~,-"G Implicit in the recent interest is the recognition that care- ful behavioral study of young children will contribute significantly to our understanding of individual differences in primary reactivity, a basic un- resolved problem in child development. Although it lms been suggested and presumed that early characteristics of individuality are significant determiners of both normal and pathologic psychological development, ",7,13,19,-"t,~ a paucity of detailed developmental information makes it difficult to evahmte tim precise relation of initial individuality to psychological growth. TM

The existence of such primary and possibly constitutional behavioral elmraeteristics is also suggested by tim accumulated data which do not sup- port the hypothesis of a one-to-one relationship of parental attitudes and practices and other environmental features to the course of the child's psycho- logical development. "~,~4,-~~ While it is clear tlmt these experiential forces profoundly influence the child's functioning, a substantial degree of variance suggests that other factors exert significant influence. Among these factors the organismic clmracteristics of the infant may very well have an important influence on determining psychological development.

A number of studies have reported observations on individual differences in the infant and young child in specific, discrete areas such as motility, 9 per- ceptual responses, 3 sleeping and feeding patterns, s drive endowment, ~ quality and intensity of emotional tone, 17 social responsiveness, a~ autonomic response patterns, ~.r-','-''-' biochemical individuality, 18,-~s and electroencephalographic patterns. -"r These various reports emphasized that individual differences appear to be present at birth and are not determined by postnatal experience. A1- though these studies Imve provided valuable data and leads for further investigation, there remains the need for a systematic and comprehensive approach to the question of behavioral individuality in childhood. This is neither due to a dearth of behavioral studies, nor to a lack of concern with the development of effective methods for the collection and analysis of developmental data through longitudinal study. However, the general result, as described by a recent exhaustive survey of the literature, has been tho accumulation of "incredible amounts of data which defy any degree of organized analysis and have no relation to a specific, experimentally posed

Presented at New York Divisional Meeting of American Psychiatric Association, Noccmber 29, 1959. This study was aided in part by grants from The National Institute o] Mental llealth (M2805) and the Gralnlck Foundation.

103

104 TIIOMAS, CIIESS, BIRCII AND IIERTZIG

h)q~othesis. Much of this research, therefore, never reachcs the manuscript stage, anti if it does, it is formnlatcd as impression of the author or as case histories. ''''~ The problems of such longitudinal studies are seen as small samples, poor testing, and the inability to convert theoretic hypotheses into experimental or operational terms which will identify significant variables.

The present paper reports a longitudinal study of individual behavioral characteristics in children, started in 1956 and comprising a series of 105 children. Tile paper will report on the existence of primary initial patterns of reactivity in infancy and on the stability of these characteristics through the first two years of life.

METHOO

The dilficultics in longitudinal studies of behavioral developmcnt have stemmed from three sources: (1) the contamination of the basic data by a confusion of observation with interpretation; (S) the absence of an economical procedure which would permit the gathering of detailed and pertinent be- havioral data from a sufficiently large sample; (3) the failure in the analysis of behavioral data to distinguish between the specific content of the behavior observed, which necessarily changes in growth, from the underlying struc- ture or pattern which may be constant.

We have considered elsewhere in some detail the problems which derive from the contamination of first order data by a pr ior i interpretation. -0~ Most frequently, this error is evidenced by the equivalent treatment of behavioral fact and psychodynamic interpretation, vide . ~~

�9 To obtain detailed longitudinal data on a sufficiently large sample of children for the specification of a variety of initial individual patterns of reactivity, it is necessary to define a readily available and investigatively economical source of data. The direct longitudinal observation of the child would "require a ratio of one investigator to each child. Consequently, serial cross-sectional study has been substituted in many instances for longitudinal inquiry. ~7 It has appeared to us that the parent represents a most vahmble source of continual direct observation,, and that parental experience, if ade- ~iuately assessed, constitutes a basic and economical source of longitudinal information. The following problems arise in the use of the parex.lt as a source of data: (1) can the parent supply sutticient explicit behavioral in- fcrmation for analysis? (2) is this information adequate for studying the problem at issue? (3) are the observations valid reflections of the child's actual functioning? !f these questions can be answered in the affirmative, then information on a. !arge sample of children can be obtained which could otherwise only be. gathcr.ed by a large core of investigators who live in the homes of the subiects ~ To answer these questions, a structured interview of the parents "!ms been utilized. The validity of these data has been checked by comparison with direct observations of the child's behavior.

The distinction between the content and the formal characteristics of behavior is crucial in the longitudim~l study of behavioral stability. It is a truism that content is by definition continuously changing and therefore necessarily unstable as an index of the persistence of individual attributes of

PRI.NfAIIY I1EACTION I'A'I-I'ERNS IN CIIILDI1EN 1 0 ~

funct ion. By contrast , formal characterist ics of behav io r m a y be constant w i th in a f r amework of chang ing content . Thus, d is t rac t ib i l i ty as a formal

character is t ic may be expressed in terms of tile ease wi th wh ich bot t le feed- ing is in te r fe red wi th b y external s t imula t ion at age six months , a nd in the

ready d i s tu rbance of ongo ing academic work by ext raneous noise in the

school years. In each case the formal aspects are the same, though the conten t

of behavior is marked ly different. I n the presen t s tudy, a t t en t ion is directed

to the formal and not the con ten t aspect of behavior .

The Interview

The first history is taken when die child is 2 to 3 mouths old. This is repeated every 3 months for a year, and thereafter at 6 month intervals, lntcrview data at five points were obtained over flae first two )'ears of life. Tile interviews at each period were scored in accordance with tile procedure to be described. The interview has been supplemented by varions type.s of direct observation of the child: in the home, in free play in a standard play room, during the administration of a standard psychological test, and in nursery school.

In gathering longitudinal behavioral data to test the hypothesis of continuity in reaction type, certain principles were strictly observed, to permit objective analysis and inde- pendent replication.

1. Behavior is described in objective terms. Strict avoidance of i,lterprctations of be- havior by parents, interviewer or observer is maintai,led throughout. Thus, a statement "the baby hated his cereal" or "he loved his bath" is considercd as unsatisfactory for primary data. Instead, tile question is always asked "what did he do that made you think he loved or hated it" and a detailed description of the child's actual behavior is recorded. In this way the contamination of the raw data by interpretations based on preconceptions, evident in a number of studies, is avoided. Since interpretations of :t specific item Of a cltild's behavior by several simultaneous observers may vary greatly, it is difficult if not impossible to obtain accurate and rcdnplicable data on an interpretative basis.

2. The basic data are obtained from the details of the child's hehavlor in the natural daily activities of his life. These include, among others, sleeping, feeding, dressing, bathing, nail-cutting and hair-brnshing in the young infant. As the child grows older, other activities such as involvement with individual people, play, toileting, vaccinations, discipline, etc. are added. Detailed information on tlle child's behavior in his daily lifo insures that tile data will reflect the child's characteristic modes of fimctioning. This procedure is in contrast to those methods which by relying primarily on observations made in unfamiliar testing situations, raise questions of atypical and unrepresentative behavior in such artificial settings.

3. In comparing the characteristics of responses among infants, obtained differences may be due to two factors. On tlle one hand the stimnlns may vary in intensity or in quality. On the other hand, the stimulus may be constant but differences derive from individual differences in reactivity. This latter factor is the principal focus of interest in this study. Itowevcr any attempt to define tlle variations in the individual response of different infa,lts by presenting them with tile same consta,lt sti,nulns would be limited and even undesirable. Such constancy involves artificial test situations, which introdt,ce such new and uncontrolled variables, as strange e,wironment, special manipulations, and testing devices. Furthermore, a controlled, delineated set of stimuli may elicit responses which represent only a narrow segment of the child's pattern of reactivity.

Tile present study, therefore, starts with the assumption that no special advantage derives from constancy of stimt,li. By acquiring infornmtion on the infant's behavioral responses in as many types of situations as possible the data sample becomes representative of the child's fimctioning. This range of information has been obtained by determining the specific responses which a baby nmkes to tile variegated features of day-by-day living, such as the bath, the taste of different food, periods of food deprivation, loud noises, the crib, bright lights, and so on. The data thus comprise a record of the responses to different stimuli of varying intensity and quality.

106 TIIO.XIAS, CIIESS, BIRCII AND IIERTZIG

In contrast with tile ~rtificialit~, of the limited experiment, this method bases itself on the classic approach used in biological field studies of function in living organisms, namely, the delineation of behavior within the environmentad context in which it occurs. The major goal is to obtain detailed and accurate data with regard to a co~Lsi.~tent type of rcactio~l pat- tert~ in the indicidual infant, whether responding to a hunger stimulus, tho taste of new food, the temperature of tile bath water, or an attitude of tile mother.

4. In data collection special emphasis is placed on the rccording of the details of tile child's first response to a new stimulus and his subsequent reactions on cxposure to the same stimulus until a consistent, long-term response has been established. Such stimuli may be simple, as tile first bath, or tile introduction of a new food; they may be. complex, as tile move to a new home or the introduction of a new person into tile house- bold. In either case the sequence of responses to new stinudi can give very valuable informa- tion as to the individual pattern of reactivity of tile child.

M e t h o d for Al~alysis of Behavior Protocols

In order to make interperiod comparisons of behavioral reactivity, nine categories for scoring responses were cstablishcd by an inductive content analysis of the interview protffcols of tile first 02 children studicd. This proccdure avoided the imposition of aprioristic categories derived a priori frmn theoretical schemes. From tile inductive content analysis tile following nine categories were found to be present and scorable in tile interview protocols from early infancy through tile second year of life:

1. Acticity Level: tile motor component present in a given child's fonctioning and tile diurnal proportion of active and inactive periods. Protocol data on motility during bath- ing, eating, playing, dressing and handling, as well as infonuation concerning tho sleep- wake cycle, reaching, crawling and walking are used in scoring this category.

2. Rhythmicity: the predictability and/or tile unpredictability in time of any function. It can be analyzed in relation to tile sleep-wake cycle, hunger, feeding pattern and elimina- tion schedule.

3. Al;l;roach or "~Vitl~drawal: tile nature of the response to a new stimulus, be it a new food, new toy or new person.

4. Adaptability: responses to new or altered situations. One is not concerned with the nature of tile initial responses, but with the ease with which they are modified in desired directions.

5. Intensity o[ Reaction: the energy level of response, irrespective of its quality or direc- tion.

6. ThreshoM or Respolt~iveness: tile intensity level of stimulation that is necessary to evoke a discernible response, irrespective of the spccifie form that the response may take, or the sensory modality affected. Tile behaviors utilized are those e0nceming reactions to sensory stimuli, environmental objects, and social contacts.

7. Quality o/Mood: the amount of pleasant, joyful and friendly behavior, as contrasted with unpleasant, crying and unfriendly behavior.

8. Distractibility: tile effectiveness of extraneous enviromnental stimuli in 'interfering with or in altering the direction of the ongoing behavior.

9. Atteution Span and Persistc~ce: two categories which are relatcd. Attention span con- cerns tile length of time a particular activity is pursued by tile child. Persistence refers to the continuation of an activity in tile face of obstacles to the maintenance of tile activity direction.

Each category was scored on a three point scale, in terms of two polar extremes, high and low, and one intermediate level. Therefore, every behavioral record was scored for each of the nine categories on a three point scale and resulted in a specific item sum for each category of reactivity.

Each protocol is analyzed for each category independently. No successive intervlewg of a gi~,ien child are scored contiguously. This segmented scoring is done to avoid contamina-

PRI.XIAHY IIEACTION PATFEIINS IN CtlILDIIEN 107

tion by "halo" effects, whereby the scorer's judgment on one category or interview might be influenced by a judgment already made on another.*

In the gathering of data, as well as in its scoring, use is made of objective, descriptive items, and interpretation is avoided. For example, a statement "he cried because he was hungry" is scored only with regard to the fact of citing. The child may or may not have been lmngry, but there is no doubt that lie did cry. In training scorers it was found that disagreements derived from attempts to score behavioral descriptions that were not explicit. In such instances the scorer had recorded his interpretation of what the statement meant, since it was impossible to determine the exact meaning because of the amhiguity of the statement. This difficulty was eliminated by strict adherence to the rule that any item where the description was ambiguous or vague was not to be scored.

A few typical behavior items and their scoring will now be given to illustrate tile general approach. The item "he lies quietly in the bath and doesn't kick" is scored as low activity level. "He ate cereal well the first time I gave it to him" is scored as an approach response. "At first he spit out his egg but after the third time he took it" is scored as high adaptability. "If he has a bowel movement he is cranky and fusses until I change him" is scored as low threshold of responsiveness. Single behavioral items are frequently scorable in two or more categories. For example, the statement "he kicks wildly, gurgles happily and laughs loudly in his bath and has done so from the very first time" can be scored as (1) high activity level, (2) initial approach, (3) positive mood and (4) intense response. The item "he kicks and whimpers when he has his nails cut, but if we talk to hiln or show him a toy he is quiet" is scored as (1) high activity level, (2) negative mood, (3) mild in- tensity and (4) distractibility.

As would be expected, the various parents have shown great variation in the quality of their spontaneous descriptions of their children's behavior. Some are factual and objective, other are subjective and interpretative or concerned with value judgments, some are con- cise and otJlers ramble. There is also great variation in the wealth of detail given regarding various tiems of behavior, tlowever, our interview technique which insists on answers in terms of specific factt, al details of behavior can elicit a great deal of such objective data even from mothers who are subjective, interpretative, preoccupied with value judgments, ramble or otherwise tend spontaneously to report insufficient descriptive items. The factual data from any one interview can be broken down into an average of 60 to 70 scorable items of behavior in each case.

The reliability of the scoring technic was tested by comparing the results obtained by two independent judges in the scoring of a series of 22 consecutively obtained cases. Ninety per cent agreement was obtained. This high level of interscorer reliability was confirmhd by comparing the results obtained by two additional scorers who lmve been trained recently in this work. Close agreement with the original score was also found in the blind scoring of the same record by the same scorer after an interval of several monflas.

A final point of method concerns the validity of the parental interviews, namely the de- gree to which these reports give an accurate description of the essential characteristics of the child's behavior. This was tested by obtaining two to three honr periods of direct ob- servation of the child in the home by two indcpcndent observers on separate occasions in 18 unselected cases, and by one observer in five other cases. The protocols of these direct observations were compared with the data reported in the parent interview. It was found

*A study of the degree to which whole protocol scoring was influenced by content was done by the method of snip-analysls. Individual behavior descriptions of nine (9) protocols were snipped, c_oded, mounted on cards and scrambled. These isolated bits were then scored to criteria. Upon the completion of scoring itelns were reassembled and the com- posite scores were Compared with the scores made on the continuous whole protocols. No significant differences in scoring were obtained between whole and snipped analysis of the data by 3 independent data analysts.

108 TIIf).XIAS, CIIESS~ "I3IRCII AND IIER'I'ZIG

that tile direct observation agreed with tile data reported at the interview closest in time to the observation with a confidence level between 0.05 and 0.01. This qt,antitative detcrmin,'x- tion of tile validity of the parental reports is further sustained 1)y the many observations of the children made by examiners as they interviewed the parents in the home.

SUBJECTS Thus far 105 children have been followed by tile procedures outlined. At

present data on 74 of these children are completely gathered through tile second year of life, and fully analyzed for consideration in this report.

The families studied represent a fairly homogeneous middle and upper middle-class group. A few of the mothers work full-time, some work part- time, but all accept on a conscious level their major responsibility of having to care for the baby. Child-care practices are highly similar within the group. The parents are permissive, with an emphasis on satisfying the needs of the child. Ma,ay of the fathers participate actively in the care of the child.

A fairly homogeneous group of this kind has advantages in an investigation into the occurrence of individual differences in the reactivity of children. If differences are conspicuous in the young infants of such a group they arc unlikely to be due to variations in either general social or cultural factors, or in the general child-care practices of the parents, and therefore more likely to represent dit[erences in the intraorganismie characteristics of the children studied.

RZSULTS

When scored for the nine categories it was found that the consistency in interperiod agreement was of such a magnitude that the probability of such agreement occurring by chance sampling factors alone is less tlmn 1 in 100. When each category is analyzed separately the same high level of agreement is sustained. These data leave little doubt that initially determined patterns of reactivity are persistent features of individuality in functioning during the first 24 months of life.

Since each reaction category was scored on a three position scale, lack of predictive relations would be expressed as a random movement from one scale position to another in any category from one age period to another. Such a statement of the problem permits one to determine the degree of confidence with which the hypothesis of no predictive relation can be rejected. Chi- Square analysis permitted the rejection of the null hypothesis at greater than the .01 level of confidence in each of the 74 children for whom data have been analyzed through the first two ),ears of life.

On a qualitative basis, the individual categories may be grouped into clusters. As a consequence, it may be possible to organize the data into a finite number of identifiable types of individuality. At present five cluster types have been identified: (1) Regularity, adaptibility, mild intensity, ap- preach, and positive mood; (2) Irregularity, nonadaptability, high intensity, withdrawal, negative mood, and high activity level; (3) Moderate ad,ffpt- ability, mild intensity, withdrawal, negative mood and low or moderate activity level; (4) Low threshold of response, distractability, short attention span mad low persistence; (5) Iligh threshold of response, and nondistract- ability. Various other clusters suggest themselves on qualitative inspection

PRI*fARY I1EAC;FION PATTEIINS IN CIIILDI1FI, N 109

of tile data, but a detailed quantitative analysis is now being projected and will be required for their precise delineation.

Qualitative examination of the data also permits tile delineation of another characteristic of individuality which is of special psychiatric interest. This concerns the character of the child's reactions to a new situation, whether it be the bath or tile introduction of solid food in early infancy, vaccinations or the first awareness of strangers, the attempt to enforce the prohibition of dangerous activities or tile initiation of toilet training at two ),ears, or the first contact with nursery school at three )'ears. In each instance, there is striking consistency in the pattern of the individual child's reaction to the new situation. This pattern is actually compounded from elements involv- ing certain of the nine categories defined in the quantitative analysis, namely activity level, approach or withdrawal, intensity, mood, adaptability, attention span and persistence. Some children respond qnietly and placidly to a new situation, approach it at once and adapt quickly and smoothly. At the other extreme are those children who withdraw sharply and violently from a new situation, persist tenaciously in their old behavior, and adapt irregularly and slowly. Other children show different types of admixture of these two extremes, such as.an initial withdrawal reaction of mild intensity, followed by a quick adaptation. Data for the type of reaction to new situations do not appear ccntinuously in the longitudinal study. At some age periods the infant in the usual middle-class family is exposed to a number of new situations, while at other age periods to few or none. We are at present engaged in a special study of this delineation, because of our belief that it may have special func- tional importance. The character of the initial response to new situations may. very well play an important role in the process of mastery and the develop- ment of ego functions in general. The initial reaction to social situations may affect the responses of other people !nvolved and influence the whole character of interpersonal interaction.

Other individual characteristics of reactivity can be delineated from the protocols. These include (1) quick conditionability and easy development of anticipatory responses, if, for example the hunger cry of the infant is stopped when the bib is put on preparatory to feeding; (2) variation in the intensity o f reaction to ditt'erent stimuli, manifested in the extreme by the child who has the same all-or-none intense response to all situations, versus the child who has graded, differentiated reactions to different stimuli; (3) very low threshold of responsiveness to one sensory modality, such as auditory or tactile; (4) unusually energetic sucking activity. These characteristics have each been evident in only a few of the children and have not appeared con- tinuously in the longitudinal protocols. Further study is necessa .ry to determine the nature and persistency of these characteristics as independent patterns Or derivatives of one or more of the nine general categories. It is also neces- sary to determine whether they are transient or persist in" a stable, consistent form into later childhood.

D I s c u s s I o N

The appe,'irance of definable individual patterns in the first few months of life, before the infant is capable of ideation and conceptualization, strongly

110 TIIO3IAS, CIII.I.I.I~S, BIRCtl AND IIEIITZIG

suggest their biological rather than psychodynamic basis. We have labeled and defined featnres of individuality as primary because they are evident early in extra-uterine life without appearing to be tlle consequence of any other identifiable factor. We have called them reaction patterns, and not behavioral patterns, because the individuality of each child is expressed in a specific consistent type of reactivity to stimuli, and not in any fixed content of behavior. Tile behavior content changes as ttle child develops, but the formal pattern of reactix4ty remains constant.

Our data thus far do not permit a definite answer to tlle question whether these primary reaction patterns arc of an inborn character, formed under the inllucnce of environmental factors in the first few months of life, or the result of tile interaction of both. \Ve plan to compare the types of patterns in 6 p,-drs of twins and 25 other pairs of siblings in our series; and we also intend to determine what correlations, if any, exist between tim child's pattern and the parental attitudes and practices.

I,X~PLICATm,','S Our tindings have a number of important implications for the fields of child

development and psychiatry. In the field of child-care practices, it is our strong impressio n fron/numer-

ous observations that the effectiveness of the individual parent's approach in caring for the child in feeding, sleeping, discipline and toilet training is very much intluenced by the child's primary reaction pattern. What is most effec- tive in one chihl may be ineffective and even harmful in another. We have recently discussed this question in greater detail elsewhere2

As indicated at tim beginning of this paper, various studies have shown the lack of a reciprocal relationship between environmental factors and the healthy or disturbed psychological development of the child. Le~), has sug- gested that the specific direction of psychopathology taken by children sub- jected to maternal overprotection may be determined by intraorganismic characteristics, a'~ In our own material we have already observed differences in the responses of individual children to similar environmental stresses, ditferences which appear to be related to tile character of the primary reac- tion pattern. We do not desire to minimize the importance of parental attitudes and practice or other environmental factors, as may have been the case in some studies of constitutional typologies in the past. It is our thesis that psychological development is the result of the constant, intimate interplay of environmental and intraorganismic forces. Children with similar primary reaction patterns may emerge with different personality structures and psycho- logic contents, depending on the environmental forces to which they have been subjected. On the other hand, children with similar environments may also show differing courses of psychological development, if they start with different primary patterns of reactivity.

Su,xt.xtAnX" AND CONCLUSIONS

The prcscnt study reports the results of the quantitative and qualitative analysis of behavioral data on 105 children who were studied for two years as part of an ongoing longitudinal study of primary individual characteristics

Pm,XIARY nEACTIOX PATI'ERNS IN CIIILDREN 111

of reactivity during infancy and childhood. The data Were obtained by con- ducting detailed structured parental interviews supplemented and validated by direct observations. The interviews and observational protocols were then subjected to content analysis, and quantitatively scored for 9 defined cate- gories of reactivity. The results of the quantitative analysis of protocols at five periods of development during the first two years of life were analyzed to determine the degree to which individual characteristics of reactivity already identifiable in early infancy persisted or changed during the course of development.

The results obtained provided the following findings: 1. Nine characteristics of reactivity can be identified in early infancy and

during the first two years of life: (1) Activity Level, (2) Rhythmicity of Functioning, (3) Adaptability, (4) Approach or Withdrawal, (5) Intensity of Reaction, (6) Threshold or Responsiveness, (7) Quality of Mood, (8) Dis- tractability, (9) Attention Span and Persistence.

2. The primary reaction characteristics found in the child during the first months of life are persistent and continue to be characteristic of the indi- vidual during the first two years with a reliability significant at the 0.01 level of confidence.

3. Clusters of these primary reaction characteristics have been defined by qualitative inspection and yield several patterns of reactivity resulting in a limited number of individual types which appear to have prognostic value for the development of ego functions.

The results are discussed in terms of their implications for the importance of non-psychodynamic factors in the evolution of personality, and in connec- tion with the methodological aspects of longitudinal investigation of psycho- logical development in children.

We can conclude from the evidence presented that our parental interview teclmique and content analysis procedure has permitted the gathering of meaningful, objective behavioral data in a valid, reduplicable and economical way. It is our belief that these methods can be applied to the study of the longitudinal development of large numbers of children with mental retarda- tion, brain damage and psychopathology.

REFF.RENCES

1. Alpert, A., Neubauer, P. W., and Weil, A. P.: Unusual variation in drive en- dowment. Psychoanalyt. Study of Child 11:1P~, 1956.

2. Ausubel, D. B.: Theory and Problems of Child Development. New York, Grune & Stratton, 1957 (pp. 111-113).

3. Bergman, P., and Escalona, S.: Unusual sensitivities in very young children. Psyehoanalyt. Study of Child 3--.4; 333, 1949.

4. Bridger, W. II., and Reiser, M. F.: Psy- chophysiologic studies of the neonate Psychosomat. Med. 21:265, 1959.

5. Bruch, H.: Parent education or the il-

lusion of onmipotenee. Am. J. Ortho- psychiat. 24:723, 1954.

6. Chess, S., Thomas, A., and Birch, H.: Characteristics of the individual child's behavioral responses to the environ- ment. Amer. Jour. Orthopsychiat. 29: 791-802, 1959.

7. Esealona, S., Leitch, M., et al.: Early phases of personality development. Monograph Soc. Res. Child Develop. 17: No. 1, 1952.

8. --: Emotionfil development in tile first )'ear of life. In: Problems of Infancy and Childhood. New York, Josiah Macy, Jr. Foundation, 1953 (p: 11).

J.l~. TIIO~IAS~ CtlESS~ BIRL-'II AND IIER'FZIG

9. Fries, M., and Woolf, P.: Some hypo- theses on the role of the congenital activity type in pcrsonalit'y develop- ment. Psychoanalyt. Study of Child 8:48, 1953.

i0. Frosch, J., and \Vortis, S. B.: A con- tribution to tho nosology of the impul- sive disordcrs. Am. J. Psychiat. 111: 132, 1954.

11. Gesell, A., and Ames, L. B.: Early evi- dences of individuality in the human infant. J. Genet. PsychoL "47:339, 1937.

12. Grossman, II. J., and Grcenberg, N. H.: Psychosomatic differentiation in infan- cy. Psychosomat. Med. 19:293, 1957.

13. Jackson, E.: Child'development patterns in the United States. In: Mental Ilealth and Infant Development, Vol. I, edited by K. Soddy. New York, Basic Books, 1956 (p. 87).

14. Klatskin, E. ti., Jackson, E. B., and Wilkin, L. C.: The influence of de- greo of flexibility in maternal child care practices on early child behavior. Am. J. Orthopsychiat. 26:79, 1956.

15. Levy, D., Maternal Overprotection. New York, Cohnnbia University Press, 1943.

16. Matder, M.: On child psychosis and schizophrenia. Psychoanalyt. Study of Child 7:286, 195 .9 .

17. Meili, 11.: A longitudinal study of per- sonality development. In: Dynamic Psychopathology in Childhood, edited by L. Jessner and E. Pavenstedt. New York, Grune & Stratton, 1959 (pp. 106-123, a summary of a monographic report," Anf~nge der Charakterent- wickhmg," Bern, Hans Huber, 1957).

18. Mirsky, I. A.: Psychoanalysis and the biological sciences. In: Twenty Years

of Psychoanalysis, edited by Alexander and Ross. New York, W. W. Norton, 1953 (pp. 155--176).

19. Murphy, L. B.: Psychoanalysis and child behavior. Bull.Menninger Clin. 21:177, 1957.

20. Orlansky, II.: Infant care and person- ality. Psychol. Bull. 46:1, 1949.

21. Personality in the Making--Fact-Find- ing Report of Mid-Century x, Vhite Ilouse Conference on Children and Youth, edited by It. L. Witmer and R. Kotinsky. New York, Harper & Bros., 1952 (pp. 35--36).

22. Richmond, J. B., and Lustman, S. L.: Antonomie function in the neonate. Psychosomat. Med. 17:269, 1955.

23. Stevenson, I.: Is the human personality lnore plastic in infancy and child- bond? Am. J. Psychiat. 114:152, 1957.

24. Stone, A. A., and Onqt,e, G. C.: Longi- tudinal Studies of Child Personality. Cambridge, Harvard University Pl'ess, 1959 (p. xiii).

25. Thomas, A., and Chess, S.: An ap- proach to the study of sources of in- divid,al differences in child behavior. J. Clin. & Exper. Psychopathol. 18: 347, 1957.

26. Tyler, L.: Psychology of lluman Dif- ferences, 2nd ed. New York, Appleton- Century-Crofts, 1956 (pp. 17-18).

27. \Valter, G.: Electroencephalographie de- velopment of children. In: Discussion on Child Development, Vol. I, edited by J. M. Tanner and B. Inhelder. New York, International Universities Press, 1953 (pp. 139.2---160).

28. Williams, R. V.: Biochemical Individ- uality. New York, John Wiley & Sons, 1956.

Alexander Thomas, M.D., Associate Pro[essor o[ Psychiatry, New York University College o[ Medicine, New York, N. Y.

Stella Chess, M.D.,: Associate Clinical Pro[essor o[ Psychiatry, New York Medical College, New York, N. Y.

Herbert Birch, Ph.D., Consultant, Association [or Aid O[ Crippled Chihlren, New York, N. Y.

Margaret E. Hertzig, A.B., Fourth )'car Medical Student, New York Unicersity College of Medicine, New York, N. Y.