|Activity, Energy Expenditure and Energy Requirements of Infants and Children (International Dietary Energy Consultative Group - IDECG, 1989, 412 pages)|
|Temperament, activity and behavioral development of infants and children|
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).