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A second approach to looking at activity level in studies of energy intake and energy requirements is to ask the question: what might be the potential role of activity level in the process wherein inadequate energy intake is translated into deficits in behavioral development? One possibility that has been suggested is that less active children are less able to elicit developmentally facilitative interactions from caregivers in their environment. For example, as hypothesized by Chavez and Martinez: "Malnutrition depresses activity which in turn isolates the individual from... necessary interaction with the mother and the family, and from all sources of stimuli that are of vital importance to the functional development of the brain." (CHAVEZ and MARTINEZ, 1984, p. 319).
Underlying this quote is the assumption that more active children will be better able to elicit developmentally facilitative interactions from their primary caregivers. However, at least within the temperament literature, this assumption has not received strong empirical support. Indeed, much of the available evidence relating children's activity levels to subsequent parent behaviors is either inconsistent (BATES, 1989b) or suggests that less active children are more likely to elicit optimal parental behaviors than are more active children (DUNN and PLOMIN, 1986; Buss, 1981).
There are several reasons for this state of affairs. First, within the framework of Bell's (BELL and CHAPMAN, 1986) control model, parents tend to act to restrain the behavior of their highly active children and to stimulate the behavior of their less active children. Since parents attempt to modulate their child's activity to an optimal level, we should not necessarily expect that more active children would receive more stimulation from their parents (BELL and CHAPMAN, 1986).
Second, as noted by BATES (1987), specific parent reactions are not automatically elicited by differences in their child's temperamental activity level. Rather, parental reactions appear to be a combined function of the child's activity level, the behaviors the child is displaying while being active (i.e., constructive versus active behaviors) and by the parents own individual tolerance for high or low activity levels. For example, data by HUBERT and WACHS (1985) indicated that up to 40% of the parents in our sample equated temperamentally-based high activity of their infant with greater perceived difficultness of the infant; nearly 20% of the sample felt that the more curious or exploratory their infant was, the more temperamentally difficult their infant was. Examination of the rationale for these ratings suggested that many parents see high mobility as necessitating greater supervisory efforts by the parents, while high levels of exploratory behavior or curiosity are viewed as an example of demanding behavior by some parents.
In addition to differential parental tolerance, differential reactivity by parents to their child's characteristic behaviors also appears to be a function of parental skill factors. For example, as noted by SUPER et al. (1981), the reaction of Colombian mothers to differences in their infant's state differed as a function of whether or not the mother had received training in facilitating infant development.
What the above suggests is that the assumption that more active children will receive more facilitative caregiver behaviors is not necessarily valid. While some evidence suggests that more active children do receive more facilitative caregiver behavior (CHAVEZ and MARTINEZ, 1984), the totality of evidence does not allow us to accept that this conclusion holds for all cases. Rather, congruent with our earlier discussion about activity level as an index of information processing, it seems clear that an adequate understanding of the relation of child activity level to caregiver behaviors necessitates more than just measuring activity level per se. Rather, the parents' characteristics, the parents' affective reaction to high or low activity level and the content of the child's activity must be assessed and integrated into our model, before we can come to a clear understanding of the relation of activity level to caregiver-child interaction patterns.
A second approach to understanding the process whereby activity level relates to decrements in behavior is to consider the possibility that activity level may act as potential mediator of the environment (BARON and KENNY, 1986). Over 25 years ago, based on clinical observations, ESCALONA (1963) suggested that inactive infants showed better development when guided by maternal interactions, whereas more active infants did best when caregivers played a less involved role. A few years later, SCHAFFER (1966) published a paper suggesting that more active children are more resistant to the detrimental effects of prolonged hospitalization than are less active children. It was unclear, however, whether the group differences reported by Schaffer were a function of differential reactivity of more and less active children to the environment or were due to differential treatment of more and less active children by hospital personnel. This line of research was not followed up very much until several years ago, when I presented data indicating that parental mediation of the environment for the child was particularly critical for the development of mastery motivation in temperamentally less active babies; in contrast, for highly active babies, confirming Escalona's original suggestion, parental mediation tended to inhibit the development of mastery motivation (WACHS, 1987b). Particularly critical in this study is the fact that there were no differences in the measured home environments of more and less active children. Thus, the results suggested differential reactivity of more and less active children.
Following up this line of research, a student of mine, Mary Jane Gandour, in her dissertation utilized a different measure of the environment (parental attention focusing behavior) and a different outcome measure (toddler exploratory behavior). Her results essentially replicated my earlier findings. Specifically, for temperamentally more active toddlers, greater amounts of parental attention focusing tended to inhibit exploratory behavior, whereas for less active toddlers, parental attention focusing tended to facilitate the development of exploratory behavior (GANDOUR, 1989). Analysis indicated no differences in the measured environments of more and less active toddlers, again suggesting differential reactivity. What this line of research suggests is that the child's temperamental activity level may be a critical mediator of the child's interaction with its environment.
What are the implications of the above findings for energy intake and energy requirement studies? First, I would remind you that imbalances between energy requirements and energy expenditure do not occur randomly. Rather, these imbalances covary with a variety of other factors, including adequacy of the child's rearing environment GRANTHAM-McGREGOR 1984; POLLITT, 1988; RUSH, 1984). Thus, I would suggest that we cannot understand how variability in energy intake and energy requirements translates into variability in behavioral development, unless we know something about the nature of the psychosocial rearing environment the child encounters. I would also suggest that we cannot fully understand the relation of psychosocial rearing factors to behavioral development, unless we know something about the role of child characteristics, such as activity level, which may mediate environmental influences (WACHS and GRUEN, 1982).
Viewing this within a synergistic framework (LESTER, 1979), let me suggest the following process model. Children who are low in activity due to reduced energy intake may be more in need of increased stimulation from their parents or caregivers than highly active children. However, if these caregivers also have a low energy intake, then they may be less able to provide the extra stimulation their children need (CRAVIOTO and DELICARDIE, 1972; POWELL and GRANTHAM-McGREGOR 1985). Under these conditions, the impact upon development of low energy intake of the child may by synergistic. First, to the extent that imbalances between energy requirements and energy expenditure adversely influence central nervous system development (CRNIC, 1983), these children are at risk. Second, to the extent that the low energy intake level of these children means that they have lower activity levels, these children will also have a greater need for active intervention from their caregivers, which means that they are at double risk. To the extent that the low energy intake of the caregivers prevents them from providing the extra stimulation that these children need (over and above normal levels of stimulation) means that these children are at even greater risk. 4
To the extent that low energy intake covaries with morbidity, which in turn may influence activity level, suggests that these children may be at an even greater level of risk (POLLITT, 1983).
However, the above model, while congruent with available data may, in fact, be oversimplistic. As presented here, the proposed model seems to suggest that all aspects of development may be equally influenced by the risk factors described above. However, it is becoming increasingly apparent from studies of environmental influences upon development that the environment does not act in a global, all or none fashion, but rather in a highly specific manner. That is, specific aspects of the environment influence specific aspects of development (WACHS and GRUEN, 1982).
The fact that specific predictors
appear to be uniquely related to certain specific outcome dimensions is not a new finding,
even in the nutritional literature. Prior research from the Bogota intervention project
(WABER et al., 1981) suggests that nutritional supplementation primarily affects
motor development, as compared to educational intervention which appears to uniquely
affect early learning. Supporting this hypothesis, in data from the Egyptian project
(WACHS et al., 1988), we reported a complex interaction suggesting that, for less
adequately nourished children, the impact of caregiver interactions was primarily upon the
child's emotionality and state control, whereas for more adequately nourished children
caregiver influences were reflected in the child's interaction with the environment. The
implication of these data for studies relating energy intake and energy requirements to
activity, is that, to understand the contribution of activity, we need to look beyond
activity level and the quality of the child's psychosocial transactions with the
environment. In these studies, we also need to measure multiple aspects of the child's
development and cannot rely upon a single outcome measure.
In regard to the use of activity level in studies of energy expenditure and energy requirements, the following facts seem well established:
1. Activity level can be influenced by inadequate energy intake.
2. At a behavioral level, activity level can also be viewed as a dimension of children's temperament.
3. Energy-based differences in activity level can be viewed as reflecting part of the constitutional contribution to temperament.
4. There are a variety of valid approaches to assessing temperamental activity at a behavioral level.
Given these facts, if the goal of the researcher is to study the influence of energy expenditure and energy requirements upon activity level per se, with no attempt to generalize beyond activity level or to discuss the implication of reduced activity levels for developmental outcomes, then he can safely ignore most of what is discussed in this paper and concentrate only on the section involving measurement. However, if the goal of the researcher is to generalize beyond activity level per se, and attempt to draw conclusions about what are the developmental implications of reduced activity level, then a new set of facts become salient:
1. The use of activity level as a proxy for other processes such as exploration or information processing is simply not sufficient. To understand the developmental processes involved in reduced activity level, the researcher must also look at what the child is doing while being active. In addition, and perhaps more critically, in understanding the developmental implications of variability in activity level, it is imperative for the researcher to determine whether or not the activity level displayed by the child is appropriate for the context the child is functioning in, and whether the child can modulate activity level across contexts.
2. Just as one cannot assume that high activity level means more information intake by the child, the researcher also cannot assume that active children are more likely to elicit developmentally facilitative stimulation from their caregivers. To understand the role of children's activity upon caregiver-child transactions, it is also critical to investigate the way in which the caregiver views the child's activity level along a positive-negative dimension, as well as studying the strategies the caregiver has available to deal with differences in children's activity levels.
3. Theoretically, children whose activity is reduced due to inadequate energy intake should be at greater risk for developmental problems, since these children also have a greater need for adult involvement and adult mediation of the environment. However, without direct measurement of the nature of caregiver-child transactions we can say little about whether the actual risk encountered by the child is equivalent to the expected risk.
To the extent that the researcher wishes to draw developmental implications from studies of activity level, one major conclusion thus can be drawn: The interrelation of energy intake, energy requirements and activity level must be looked at within a multidimensional framework, emphasizing the process wherein energy intake, energy expenditure, activity, contextual factors, and the child's environment relate to different outcome variables, rather than assuming a linear or unidimensional relation. Many of the issues I have raised here have also appeared in the nutrition literature. For example, in the current debate on the "small but healthy" hypothesis, SCRIMSHAW and YOUNG (1989) invoke the concepts of physiological and behavioral adaptation and accommodation. In my reading of this paper, it seems clear that neither behavioral adaptation nor behavioral accommodation can be understood without taking into account contextual factors, specifically what the culture or the environment requires of the individual. Clearly, there seems to be a parallel here with my comments on the necessity for taking context into account when discussing activity level. Similarly, BEATON (1989), when discussing the relevance of anthropometric variables for the small but healthy controversy, makes the point that a complete understanding of the relation of protein-calorie intake to function means that we must go beyond height and weight markers and utilize a process approach. Again, there is a parallel between what Beaton suggests and the points I have raised about the necessity of going beyond activity markers and looking at process. The use of marker variables like activity level or height and weight may indeed be parsimonious, but there are different ways of interpreting parsimony.
Let me close with a quote from an
earlier paper of mine, concerning the adequacy of existing environmental action models for
explaining variability in behavioral development. I believe this quote is also relevant
when we look at studies relating energy intake and energy requirements to behavior and
development: "In terms of theory, we have for the most part reified the law of
parsimony... However, properly interpreted, the law of parsimony does not refer to the
simplest explanation per se, but rather the simplest explanation given the nature of the
phenomena. As McCALL and McGHEE (1977) have noted, there is no a priori reason to
assume that nature is necessarily parsimonious when it comes to human development"
(WACHS, 1986, p. 274).
I wish to thank Jack Bates and
Avanelle Kirksey for their reading and commenting on a preliminary draft of this
ANDERSON, P.: More is different. Science, 177, 393-396 (1972).
BARON, R., KENNY, D.: The moderator-mediator variable distinction in social psychological research. J. Pers. Soc. Psychol., 51, 1173-1182 (1986).
BARRETT, D., RADKE-YARROW, M.: Effects of nutritional supplementation on children's responses to novel, frustrating and competitive situations. Am. J. Clin. Nutr., 42, 102-120 (1985).
BARRETT, D., RADKE-YARROW, M., KLEIN, R.: Chronic malnutrition and child behavior, Dev. Psychol., 18, 541-556 (1982).
BATES, J.: Temperament in infancy. In: Handbook of Infant Development, 2nd ea., J. OSOFSKY (Ed.). Wiley, New York, NY, 1987.
BATES, J.: Concepts and measures of temperament. In: Handbook of Temperament and Childhood, G. KOHNSTAMM, J. BATES, M. ROTHBART (Eds.). Wiley, Sussex, 1989a.
BATES, J.: Application of temperament concepts. In: Handbook of Temperament in Childhood, G. KOHNSTAMM, J. BATES, M. ROTHBART (Eds.). Wiley, Sussex, 1989b.
BATES, G., BAYLES, K.: Objective and subjective components in mothers' perceptions of their children from age 6 months to 3 years. Merrill-Palmer Quarterly, 30, 111 -130 (1984).
BEATON, G.: Small but healthy? Are we asking the right question. Hum. Org., 48, 30-38 (1989).
BELL, R., CHAPMAN, M.: Child effects in studies using experimental or brief longitudinal approaches to socialization. Dev. Psychol., 22, 595-603 (1986).
BELSKY, J., MOST, R.: From exploration to play: A cross sectional study of infant free play behavior. Dev. Psychol., 17, 630-639 (1981).
BERLYNE, D.: Conflict, Arousal and Curiosity. McGraw Hill, New York, NY, 1960.
BUSS, A., PLOMIN, R.: Temperament: Early Developing Personality Traits. Erlbaum, Hillsdale, NJ, 1984.
BUSS, D.: Predicting parent child interactions from children's activity level. Dev. Psychol., 17, 59-65 (1981).
CHAVEZ, A., MARTINEZ, C.: Behavioral measurements of activity in children and their relation to food intake in a poor community. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
CRAVIOTO, J., DELICARDIE, E.: Environmental correlates of severe clinical malnutrition and language development in survivors from Kwashiorkor or Marasmus. In: Nutrition, the Nervous System and Behavior. PAHO Scientific Publication, 251, 1972.
CRNIC, L.: Effects of nutrition and environment on brain biochemistry and behavior. Dev. Psychobiol., 16, 129-145 (1983).
DENENBERG, V.: Stimulation in infancy, emotional reactivity and exploratory behavior. In: Neurophysiology and Emotion, D. GLASS (Ed.). Rockefeller University Press, New York, NY, 1987.
DENENBERG, V.: Experimental programming of life histories in the rat. In: The Functions of Stimulation in Early Postnatal Development, J. AMBROSE (Ed.). Academic Press, London, 1969.
DEVRIES, M.: Temperament and infant mortality among the Masai of East Africa. Am. J. Psychiatry, 10, 141 (1984).
DUNN, J., PLOMIN R.: Determinants of maternal behavior toward three year old siblings. Br. J. Dev. Psychol., 4, 127-137 (1986).
EATON, W.: Measuring activity level with actometers. Child Dev., 54, 720-726 (1983).
EATON, W., DURESKI, C.: Parent and actometer measures of motor activity level in the young infant. Infant Behav. Dev., 9, 383-393 (1986).
EATON, W., ENNS, L.: Sex differences in human motor activity level. Psychol. Bull., 100, 19-28 (1986).
EATON, W., ENNS, L., PRESSE, M.: Scheme for observing activity level: Reliability and convergent validity. J. Psychoeduc. Assess., 3, 273-280 (1987).
EPSTEIN, S.: Aggregation and beyond: Some basic issues in the prediction of behavior. J. Pers., 51, 360-397 (1983).
ESCALONA, S.: Patterns of infantile experience and the developmental process. Psychoanal. Study Child, 51, 360-397 (1963).
GANDOUR, M.: Activity level as a dimension of temperament in toddlers: Its relevance for the organismic specificity hypothesis. Child Dev., 60, 1092-1098 (1989).
GOLDSMITH, H., Buss, A., PLOMIN, R., ROTHBART, M., THOMAS, A., CHESS, S., HINDE, R. McCALL, R.: Round table: What is temperament? Four approaches. Child Dev., 58, 505-529 (1987).
GOLDSMITH, H., CAMPOS, J.: Toward a theory of infant temperament. In: The Development of Attachment and Affiliative Systems, R. EMDE, R. HARMON (Eds.). Plenum, New York, NY, 1982.
GOLDSMITH, H., RIESER-DANNER, L.: Assessing early temperament. In: Handbook of Psychology and Educational Assessment of Children, Vol. 2, C. REYNOLDS, R. KAMPHAUS (Eds.). Guilford, New York, NY, in press.
GOLDSMITH, H., ROTHBART, M.: The laboratory temperament assessment battery (LAB-TAB). Oregon Center for the Study of Emotion, Technical Report 88-01. Department of Psychology, University of Oregon, Eugene, Oregon, OR, 1988.
GOODRICK, C.: Variables effecting free exploration responses of male and female Wistar rats as a function of age. Dev. Psychol., 4, 446-446 (1971).
GRANTHAM-McGREGOR, S.: Chronic undernutrition and cognitive abilities. Hum. Nutr. Clin. Nutr., 38, 83-94 (1984).
HALVERSON, C., POST-GORDON, J.: Measurement of open field activity in young children: A critical analysis. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
HORTON, E.: Appropriate methodology for assessing physical activity under laboratory conditions in studies of energy balance in adults. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
HSU, C.: SOONG, W., STIEGLER, J., HONG, C., LIANG, C.: The temperamental characteristics of Chinese babies. Child Dev., 52, 1337-1340 (1981).
HUBERT, N., WACHS, T.D.: Parental perceptions of the behavioral components of infant easy-difficultness. Child Dev., 56, 1525-1537 (1985).
HUBERT, N., WACHS, T.D., PETERS-MARTIN, P., GANDOUR, M.: The study of early temperament: Measurement and conceptual issues. Child Dev., 53, 571-600 (1982).
IRWIN, J.: Galen on the temperaments. J. Gen. Psychol., 36, 45-64 (1947).
KAGAN, J., REZNICK, S., SNIDMAN, N.: Temperament inhibition in early childhood. In: The Study of Temperament, R. PLOMIN, J. DUNN (Eds.). Erlbaum, Hillsdale, NJ, 1984.
KAGAN, J., REZNICK, S., SNIDMAN, N., GIBBONS, J., JOHNSON, M.: Childhood derivatives of inhibition and lack of inhibition to the unfamiliar. Child Dev., 59,1580-1589 (1988).
KENRICK, D., FONDER, D.: Profiting from controversy: Lessons from the person-situation debate. Am. Psychol., 43, 23-34 (1988).
LEANER, J., LEANER, R.: Temperament and adaptation across life. In: Life Span Development and Behavior, Vol. 5, P. BATES, O. BRIMM (Eds.). Academic Press, New York, NY, 1983.
LESTER, B.: A synergistic process approach to the study of prenatal malnutrition. Int. J. Behav. Dev., 2, 377-393 (1979).
MALINA, R.: Physical activity and motor development - performance in populations nutritionally at risk, In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
MATHENY, A.: Bayley infant behavior record: Behavior components in twin analyses. Child Dev., 51, 1157-1167 (1980).
MATHENY, A., BROWN, A., THOBEN, A.: Activity, motor coordination and attention: Individual differences in twins. Percept. Mot. Skills, 32, 151-158 (1971).
MATHENY, A., WILSON, R., THOBEN, A.: Home and mother: Relation to infant temperament. Dev. Psychol, 21, 486-494 (1987).
McCALL, R., McGHEE P.: The discrepancy hypothesis of attention and affect in infants. In: The Structuring of Experience, I. UZGIRIS, F. WEIZMANN (Eds.). Plenum, New York, NY, 1977.
OEHLER, J., ECKERMAN, C., WILSON, W.: Social stimulation and the regulation of premature infants state prior to term age. Infant Behav. Dev., 11, 333-351 (1988).
PAGET K., NAGLE, R., MARTIN, R.: Interrelationships between temperament characteristics and first grade teacher student interactions. J. Abnorm. Child Psychol., 12, 547-770 (1984).
PALISIN, H.: Preschool temperament and performance on achievement tests. Dev. Psychol., 22, 766-779 (1986).
POLLITT, E.: Morbidity and infant development: A hypothesis. Int. J. Behav. Dev., 6, 461-475 (1983).
POLLITT, E.: A critical view of three decades of research on the effects of chronic energy malnutrition on behavioral development. In: Chronic Energy Deficiency: Consequences and Related Issues, B. SCHÜRCH, N.S. SCRIMSHAW (Eds.). IDECG, c/o Nestle Foundation, Lausanne, Switzerland, 1988.
POLLITT, E., AMANTE, P. (Eds.): Energy Intake and Activity. Alan R. Liss, New York, NY, 1984.
POWELL, C., GRANTHAM-McGREGOR S.: The ecology of nutritional status and development in young children in Kingston, Jamaica. Am. J. Clin. Nutr., 41, 1322-1331 (1985).
POWER, T., CHAPIESKI, L. McGRATH, M.: Assessment of individual differences in infant exploration and play. Dev. Psychol., 21, 974-981 (1985).
REINA, J., SPURR, G.: Daily activity level of marginally malnourished school age girls. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
RHEINGOLD, H., ECKERMAN, C.: The infant separates himself from his mother. Science, 168, 78-83 (1970).
ROTHBART, M., DERRYBERRY, D.: Development of individual differences in temperament. In: Advances in Developmental Psychology, Vol. 1, M. LAMB, A. BROWN (Eds.). Erlbaum, Hillsdale, NJ, 1981.
ROTHBART, M., GOLDSMITH, H.: Three approaches to the study of infant temperament. Dev. Rev., 5, 237-260 (1985).
RUSH, D.: The behavioral consequences of protein energy deprivation and supplementation in early life. In: Human Nutrition, Vol. 5, J. GALLER (Ed.). Plenum, New York, NY, 1984.
SAMEROFF, A., SEIFER, R., ELIAS, P.: Sociocultural variability in infant temperament ratings. Child Dev., 53, 164-173 (1982).
SCAFIDI, F., FIELD, T., SCHANBERG, S., BAUER, C., VEGA-LAHR, N. GARCIA, R., POIRIER, J., NYSTROM, G., KUHN, C.: The effect of tactile-kinesthetic stimulation on the clinical course and sleep-wake behavior of preterm neonates. Infant Behav. Dev., 9, 91-105 (1986).
SCHAFFER H.: Activity level as a constitutional determinant of infantile reaction to deprivation. Child Dev., 37, 595-602 (1966).
SCRIMSHAW, N., YOUNG, V.: Adaptation to low protein and energy intakes. Hum. Org., 48, 20-20 (1989).
SIGMAN, M., NEUMANN, C., JANSEN, A., BWIBO, N.: Cognitive abilities of Kenyan children in relation to nutrition, family characteristics and education. Child Dev., 60, 1463-1474 (1989).
SLABACH, E., MORROW, J., WACHS, T.D.: Questionnaire measurement of infant and child temperament: Current status and future developments. In: Exploration in Temperament, J. STRELAU, A. ANGLEITNER (Eds.). Plenum, New York, NY, in press.
STRELAU, J.: Temperament, Personality and Activity. Academic Press, New York, NY, 1983.
STRELAU, J.: Do biological mechanisms determine the specificity of temperament? In: Temperament Discussed, G. KOHNSTAMM (Ed.). Sweets and Zeitlinger, Alan R. Liss, New York, NY, 1986.
STRELAU, J.: Concepts of temperament in personality research. Eur. J. Pers., 1, 107-117 (1987).
SUPER, C., CLEMENTS, J., VUORI, L., CHRISTIANSEN, N., MORA, J., HERRERA, M.: Infant and caretaker behaviors as mediators of nutritional and social interventions in the barrios of Bogota. In: Culture and Early Interaction, T. FIELD (Ed.). Erlbaum, Hillsdale, NJ, 1981.
SUPER, C., HARKNESS, S.: The infants niche in rural Kenya and metropolitan America. In: Cross Cultural Research at Issue, L. ADLER (Ed.). Academic Press, New York, NY, 1982.
THOMAS, A., CHESS, S.: Temperament and Development. Bruner-Mazel, New York, NY, 1977.
THOMAS, A., CHESS, S., BIRCH, H., HERTZIG, M., KORN, S.: Behavioral Individuality in Early Childhood. New York University Press, New York, NY, 1963.
TORUN, B.: Physiological measurements of physical activity among children under free living conditions. In: Energy Intake and Activity, E. POLLITT, P. AMANTE (Eds.). Alan R. Liss, New York, NY, 1984.
VAUGHN, B., BRADLEY, C., JOFFE, L., SEIFER, R., BARGLOW, P.: Maternal personality variables measured prenatally are predictive of ratings of temperamental difficulty on the Carey Infant Temperament Questionnaire. Dev. Psychol., 23, 152-161 (1987).
WABER, D., VUORI-CHRISTIANSEN, L., ORTEZ, N., CLEMENT, J., CHRISTIANSEN, N., MORA, J., REED, R., HERRERA M.: Nutritional supplementation, maternal education and cognitive development of infants at risk of malnutrition. Am. J. Clin. Nutr., 34, 807-813 (1981).
WACHS, T.D.: Models of physical environmental action. In: Play Interactions, A. GOTTFRIED, C. BROWN (Eds.). Lexington Books, Lexington, MA, 1986.
WACHS, T.D.: Short term stability of aggregated an non-aggregated measures of parent behavior. Child Dev., 58, 796-797 (1987a).
WACHS, T.D.: Specificity of environmental action as manifest in environmental correlates of toddlers mastery motivation. Dev. Psychol., 23, 782-790 (1987b).
WACHS, T.D.: Relevance of physical environment influences for toddler temperament. Infant Behav. Dev., 11, 431-446 (1988).
WACHS, T.D., BISHRY, Z., YUNIS, F., SOHBY, A., GALLAL, O., HARRISON, G., JEROME, N., KIRKSEY, A.: Development in Egyptian toddlers as a function of nutrition, morbidity and environment. Symposium presentation. 6th International Conference on Infant Studies. Washington, DC, April 1988.
WACHS, T.D., GRUEN, G.: Early Experience and Human Development. Plenum, New York, NY, 1982.
WHIMBY, A., DENENBERG, V.: Two independent behavioral dimensions in open field performance. J. Comp. Physiol. Psychol., 63, 500-504 (1967).
WILSON, R., MATHENY, A.: Behavior genetics research and infant temperament. In: The Study of Temperament, R. PLOMIN, J., DUNN (Eds.). Erlbaum, Hillsdale, NJ, 1986.
ZENTALL, S., ZENTALL, T.: Optimal stimulation: A model of disordered activity and performance in normal and deviant children. Psychol. Bull., 94, 446-471 (1983).
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