In the newborn infant the head represents about a quarter of the total length; in the adult it represents about one-seventh. In the newborn infant the muscles constitute a much smaller percentage of the total body mass than in the young adult. In most tissues, growth consists both of the formation of new cells and the packing in of more protein or other material into cells already present; early in development cell division predominates and later cell filling.
Different tissues and different regions of the body mature at different rates, and the growth and development of a child consists of a highly complex series of changes. It is like the weaving of a cloth whose pattern never repeats itself. The underlying threads, each coming off its reel at its own rhythm, interact with one another continuously, in a manner always highly regulated and controlled. The fundamental questions of growth relate to these processes of regulation, to the program that controls the loom, a subject as yet little understood.
In this section, the height curves of girls and boys are considered in the three chief phases of growth; that is briefly from conception to birth, from birth until puberty , and during puberty. Also described are the ways in which other organs and tissues, such as fat, lymphoid tissue , and the brain, differ from height in their growth curves.
There is a brief discussion of some of the problems that beset the investigator in gathering and analyzing data about growth of children, of the genetic and environmental factors that affect rate of growth and final size, and of the way hormones act at the various phases of the growth process.
Lastly, there is a brief look at disorders of growth. Throughout, the emphasis is on ways in which individuals differ in their rates of growth and development. The changes in height of the developing child can be thought of in two different ways: the height attained at successive ages and the increments in height from one age to the next, expressed as rate of growth per year. If growth is thought of as a form of motion, the height attained at successive ages can be considered the distance travelled, and the rate of growth, the velocity.
The blood and tissue concentrations of those substances whose amounts change with age are thus more likely to run parallel to the velocity rather than to the distance curve. In some circumstances, indeed, it is the acceleration rather than the velocity curve that best reflects physiological events.
What Is Lifespan Development?
In general, the velocity of growth decreases from birth onward and actually from as early as the fourth month of fetal life; see below , but this decrease is interrupted shortly before the end of the growth period. At this time, in boys from about 13 to 15 years, there is marked acceleration of growth, called the adolescent growth spurt.
From birth until age four or five, the rate of growth in height declines rapidly, and then the decline, or deceleration, gets gradually less, so that in some children the velocity is practically constant from five or six up to the beginning of the adolescent spurt. A slight increase in velocity is sometimes said to occur between about six and eight years. This general velocity curve of growth in height begins a considerable time before birth. Age in the fetal period is usually reckoned from the first day of the last menstrual period, an average of two weeks before actual fertilization, but, as a rule, the only locatable landmark.
There is considerable evidence that from about 34 to 36 weeks onward the rate of growth of the fetus slows down because of the influence of the maternal uterus , whose available space is by then becoming fully occupied. Twins slow down earlier, when their combined weight is approximately the week weight of a single fetus.
Babies who are held back in this way grow rapidly as soon as they have emerged from the uterus. Thus there is a significant negative association between weight of a baby at birth and weight increment during the first year; in general, larger babies grow less, the smaller more. For the same reason there is practically no relation between adult size and the size of that person at birth, but a considerable relation has developed by the time the person is two years old. This slowing-down mechanism enables a genetically large child developing in the uterus of a small mother to be delivered successfully.
It operates in many species of animals; the most dramatic demonstration was by crossing reciprocally a large Shire horse and a small Shetland pony. The pair in which the mother was a Shire had a large newborn foal, and the pair in which the mother was Shetland had a small foal. But both foals were the same size after a few months, and when fully grown both were about halfway between their parents. From an instrumental point of view, intraindividual variational change is about a skill or ability token emerging but not emergent and becoming more precise and more accurate. Intraindividual variations are generally represented as linear, as additive in nature.
As a consequence, this change is generally understood as quantitative and continuous. At any given level of form i. If thinking is understood as undergoing transformational change, then at any given transformational level, variational changes are found in variants of thought e.
If emotions are presented as undergoing transformational change, then at any transformational level, variational change is reflected, for example, in differences in the degree of emotionality more or less anxious, empathic, altruistic, and so on. If identity is thought of as undergoing transformational change, then at any transformational level, there is variational change in the type of identity assumed e.
If the structure of memory undergoes transformational change, there is variational change in memory capacity, speed of processing, memory style, and memory content. Transformational change has been identified with domain general normative structural issues such as changes that are typical of phyla, species, and individuals. In ontogenesis, for example, normative changes in cognitive, affective, and motivational systems have been the central issue of concern. The focus here is sequences of universal forms whose movement defines a path or trajectory.
Concepts of contingent rather than necessary organization, and contingent rather than necessary change, and concepts of reversibility, continuity, and cyclicity are associated with intraindividual variational change. Transformational and variational changes have also been associated with different mechanisms of change.
We are here faced with a logical difficulty. As noted earlier, developmental change entails five necessary defining features. However, as it turns out, each feature is associated with transformational change, and none are associated with variational change. Yet, it was also stated earlier that development entails both transformational and variational change. How can this be resolved? Mascolo and Fischer Chapter 6 of this volume suggest that the resolution is to identify transformational change as developmental change, and variational as historical change. The difficulty with this solution lies in its exclusivity.
The study of change with respect to the individual's acquisition of specific concepts and skills i. It would seem prudent to explore whether there might be some principled way this variational component and the transformational component might be integrated into an inclusive framework. The split resolution denies the reality of or marginalizes one type of change, thus claiming the other constitutes the really real development. The relational resolution—to be expanded later in the Relational Metatheory section—maintains that the apparent dualism, like any dualism, can better be understood as two interconnected features of the same whole.
This solution claims a reality in which the processes assume differentiated functional roles, but each process in itself explains and is explained by the other. Complex open systems by their very nature are inherently and spontaneously active; they produce acts consistent with the structure of the system flies produce fly acts; pigeons, pigeon acts; and humans, human acts. Partial success feeds back to the system, which uses the feedback as a resource in changing transforming the system. The transformed system, in turn, produces further variants of the act. As Demetriou, Mouyi, and Spanoudis Chapter 10 of this volume state: The relations between the general and the specialized processes are complex and bidirectional.
On the other hand, specialized processes provide the frame and raw material for the functioning of general processes.
On the other hand, the relational solution discourages any notion of a systems approach and an information processing approach or a social learning approach as necessarily being competing alternatives. They become competing alternatives only when they become split and one or the other claims the totality. Lewis on social understanding Chapter 17 of this volume , M.
As a microlevel example of the variational, consider Ornstein and Light's analysis. Research programs that focus on transformations of knowing and thought, moving from the concrete sensorimotor to the abstract reflective, often conceptualize these transforms as levels , including levels termed the metacognitive and the metamemorial. Although less common, some research programs explicitly incorporate both poles of the developmental whole. In this theory, a distinction is drawn between a domain general transformational system termed the competence system , and a domain specific variational system termed the procedural system.
The competence system is characterized by the acquisition of the universal logical features of reasoning, while the procedural system is characterized by highly contextualized on line processing mechanisms. In the course of discussing the concept of development, the term relational has frequently appeared. It has appeared as a metatheory at the level of a worldview. As a synthesis, relationism is composed of a coherent set of ontological and a coherent set of epistemological principles. The ontology of relationism entails a reality based on process rather than substance Bickhard, This ontology has classically been defined as an ontology of Becoming Allport, ; Overton, It includes process, activity, change, and necessary organization as defining categories.
The active organism concept is a direct consequence of the ontology of Becoming found in relationism, whereas the passive or reactive organism concept reflects the ontology of stasis and uniformity Overton, , found in the atomistic, reductionistic worldview called mechanistic. The ontologies of active versus passive organism, as M. Nevertheless, despite this importance, this section is more directly concerned with the epistemological principles of relationism. The epistemology of relationism is, first and foremost, a relatively inclusive epistemology, involving both knower and known as equal and indissociable complementary processes in the construction, acquisition, and growth of knowledge.
Cartesian dualism claims to cut nature at its joint, dividing any whole into pure forms that constitute absolutely decomposable pieces i. For example, subject is split from object, mind from body. As one example among many possible examples of fundamental split dichotomies Table 1 , consider the splitting of subject from object, mind from body.
After the split, a decision is required as to which constitutes the foundational real that will do the explaining and which constitutes the apparent real that will be explained.
- The process of growth.
- Distort Raleigh - Issue #1.
- Cognitive development - Wikipedia.
If the ontological position is that the physical constitutes the foundational real—as in all neopositivist and many behavioristic approaches—thinking, reasoning, perception, motivation, affect, and so forth must necessarily be explained by the atoms of biology genes, neurons , and the sociocultural and physical environments. The epistemology of relationism heals splits and resolves dualisms—false dichotomies—that in a postpositivist era are recognized as retardants to scientific progress.
And, importantly, relationism does this healing in a coherent, principled manner. Efforts at moving beyond Cartesian dichotomies are not new, but since the 19th century's rejection of Hegel's metaphysical system, few systematic efforts at doing this healing in a principled fashion have been attempted. Calls for relational thinking are also not new. However, neither James nor Dewey articulated an explicit set of principles designed to support this argument. However, again, despite the many calls for a relational approach to science, there has been little in the way of articulating a coherent set of metatheoretical principles that may then serve as a guide for how one actually might do relational thinking.
Relationism then is a metatheoretical space representing a synthesis of contextualism and organicism where foundations are groundings, not bedrocks of certainty, and analysis is about creating categories, not about cutting nature at its joints. In place of a rejected atomism, holism becomes the overarching first epistemological principle. Building from the base of holism, relational metatheory moves to specific principles that define the relations among parts and the relations of parts to wholes. In other words, relational metatheory articulates principles of analysis and synthesis necessary for any scientific inquiry.
Holism is the principle that the identities of objects and events derive from the relational context in which they are embedded. Wholes define parts and parts define wholes. The classic example is the relation of components of a sentence. Patterns of letters form words, and particular organizations of words form sentences.
Clearly, the meaning of the sentence depends on its individual words parts define whole.