Consideration of the anatomical characteristics of the human brain provides strong support for the plasticity of human developmental processes. As noted in Chapter 1, and as will be discussed in greater detail in a later chapter, data derived from evolutionary biology and comparative psychology indicate that animals differ in the eventual level of behavioral flexibility attained across their ontogeny. These species differences in behavior are related to corresponding species differences in the ratio of association to sensory fibers in the brain that Hebb (1949) terms the A/S ratio. As Thompson (1981) observes, “moving from more primitive to more complex mammals, following the general course of evolution, the amount of cortex relative to the total amount of brain tissue increases in fairly regular proportions” (p. 7); and although “the basic organization of the cortical sensory and motor areas does not appear to differ markedly from rat to human, … as one ascends the mammalian scale of evolution, the relative amount of association cortex (cortex that is neither sensory nor motor and is concerned with higher or more complex behavioral functions) increases strikingly” (p. 8). Moreover, the primates, and particularly Homo sapiens, exhibit “enormous and disproportionate increases in the amount of cerebral cortex” (Thompson, 1981). And among mammals, humans, although they do not have the largest brain masses, exhibit the highest A/S ratio – indeed “the majority of neurons in the human brain are in the cerebral cortex” (Thompson, 1981).

Several lines of evidence, derived from the literatures of evolutionary biology and anthropology, converge in suggesting that (1) features of human macroevolutionary change and of human microevolution provided a structural contribution to the unique degree of plasticity that characterizes humans' processes of development; (2) this evolution was both a basis of and derived from humans' behavioral, social, and cultural development; and (3) as a consequence, biological functioning and change – in regard to both ontogenetic and evolutionary progressions – are reciprocally related, first, to the social and cultural forces acting on the organism and, second, to the organism's own behavior as well. In this view, then, not only, for instance, did the evolution of the human brain enable humans to be socially responsive, but at the same time humans' social and cultural embeddedness were the key selection features for the human brain. In other words, human plasticity derives from an evolutionary synthesis between the human brain and human culture (Gould, 1977; Masters, 1978; Washburn, 1961).

Although work in support of these links has a long history, indeed dating back to at least the early nineteenth century, two lines of evidence will be presented. The first line of evidence derives from a recent, comprehensive scholarly integration of the literatures relevant to the concept of heterochrony (or differences in timing) in human evolution and development. This synthesis has been presented by Gould in his highly influential book Ontogeny and Phytogeny (1977).

Are human genetic processes sufficiently plastic to permit the development of intraindividual flexibility? Before addressing this question it is useful to consider how thoroughly human genetic endowment ensures systematic interindividual differences. Our genetic endowment provides a basis of the uniqueness of each human life and provides substance to the claim that all humans have a unique heredity–environment interactive history (Hirsch, 1970; Lerner, 1976, 1978, 1979; McClearn, 1981). Estimates of the number of gene pairs in humans typically range between 10,000 and 100,000 (Bodmer & Cavalli-Sfarza, 1976; Stern, 1973), and if one considers how much genotypic variability can be produced by the reshuffling process of meiosis occurring with 100,000 gene pairs, then the potential for variability is so enormous that “it is next to impossible that there have ever been two individuals with the same combination of genes” (McClearn, 1981, p. 19).

Indeed, Hirsch (1970) conservatively estimates that there are over 7 × 1017 (70 trillion) potential human genotypes. Bodmer and Cavalli-Sforza (1976) estimate that each human has the capacity to generate any one of 103000 different eggs or sperm; by comparison, their estimate of the number of sperm of all men who have ever lived is only 1024. Thus, considering

Perhaps more so than in any of the other disciplinary areas we have considered, the concept of “levels” and the idea that reciprocal interactions among levels provide a basis of processes' plasticity have played central roles in theory and research in comparative–developmental psychology. Moreover, while not as historically preeminent, the use of these notions specifically in the study of human ontogeny (i.e., in developmental psychology per se) is also quite important (see R. Lerner, 1976; R. Lerner & Busch-Rossnagel, 1981).

Psychological levels and functional orders

Interest in the nature of species evolutionary changes, in interspecies differences in species evolutionary changes, and in criteria for discriminating among species levels led evolutionary biologists and comparative psychologists to study the concept of anagenesis (Yarczower & Hazlett, 1977). Although a controversial idea (Capitanio & Leger, 1979; Yarczower & Hazlett, 1977; Yarczower & Yarczower, 1979), most scientists agree that “anagenesis refers to the evolution of increased complexity in some trait” (Capitanio & Leger, 1979, p. 876). For example, Dobzhansky et al. (1977, p. 236) note that “anagenetic episodes commonly create organisms with novel characters and abilities beyond those of their ancestors” or simply that anagenesis is an “evolutionary advance or change.” Similarly, Jerison (1978, pp. 1–2) notes that an evolutionary analysis of progress from earlier to later species “is called ‘anagenetic’ and is about progressive evolution” and that in such an analysis “the objective is to identify grades in evolution.”

In recent years, many social scientists (e.g., Baltes, Reese, & Lipsitt, 1980; Clarke & Clarke, 1976; Brim & Kagan, 1980) have been seriously questioning long-held conceptions of human development stressing constancy or continuity across life (e.g., see Fraiberg, 1977; Klaus & Kennell, 1976). The alternative view that has been emerging, based on increasing research evidence at levels of analysis ranging from the genetic to the cultural, stresses instead human plasticity at multiple levels of being (e.g., Cotman & Nieto-Sampedro, 1982; Greenough & Green, 1981; McClearn, 1981). Indeed, both theoretical and empirical work increasingly support the conviction that processes at any one of these levels of analysis may be linked to processes at every other level (e.g., Brent, 1978a; Magnusson, 1981; Magnusson & Allen, 1983; Prigogine, 1978, 1980).

Such developments call for a multidisciplinary reappraisal of the nature and bases of plasticity in human functioning and development and hold out the promise that multilevel multidisciplinary research and intervention will further increase behavioral plasticity and enhance human development. This revised view of the science of human behavior, which stresses complex interrelationships among the levels of human functioning – the inner biological, individual psychological, group and social network, societal, cultural/historical, and so on (Bronfenbrenner, 1977, 1979; Sarbin, 1977) – offers a perspective on causality that differs from past conceptions (Overton & Reese, 1981) and once again underscores the need for scientists to attend to the role that personal values and beliefs play in their research and intervention efforts (cf. Toulmin, 1981).

In many ways neurons are like other living cells – for example, they can generate energy and repair and maintain themselves. However, neurons have unique functions not shared with other cells. Among these specialized features is the transmission of nerve impulses and those processes associated with the ability of neurons to produce and release neurotransmitters (Iversen, 1979). More than anything else in the human brain, its neurochemical characteristics provide unequivocal evidence for the plasticity of the human organism.

According to Thompson (1981), the key to understanding the actual character of human plasticity provided by the brain lies in an understanding of the chemical synapse and thus neurotransmitters. In the human brain most of the synaptic connections among neurons are chemical. As opposed to electrical synapses, which are common in many invertebrates and which work like an electrical transformer – that is, output is determined by input and is unmodifiable – chemical synapses are very plastic (Thompson, 1981). There are over 30 different known or suspected brain transmitters; each has a characteristic excitatory or inhibitory effect on neurons (Iversen, 1979). In addition, neurotransmitters are localized in specific brain regions.

Due to advances in techniques that allow for the selective staining of neurons containing a particular transmitter, thus facilitating the study of the functional chemistry of the brain, researchers have been able to map the anatomical distribution of individual transmitters in specific neuronal pathways (Iversen, 1979).

Over the course of the last decade or so exciting changes have occurred in those areas of social science that focus on human development. A growing number of studies of infants and children, of adolescents, and of adults and the elderly have yielded results challenging long-held views about the nature of human development: that early experience virtually immutably shapes the entire life course; that development is essentially a within-the-person phenomenon, largely unaffected in quality or quantity by the context of life; and that, by and large, all people develop in fairly standard, normative ways.

The recent studies indicate that people are more resilient to early, often quite negative experiences than was previously thought, that the events of early life do not necessarily constrain developments later on. They also suggest that features of the person's historical setting may sometimes shape personality and social and intellectual functioning much more than maturational- or ageassociated changes. General events such as wars, economic privations, and political upheavals, as well as personal events such as marriage, divorce, illness, death, and career change, often profoundly affect both the quantity of life changes and the quality of the life course. Recent studies also indicate that there are multiple paths through life. As people age they become increasingly different from each other and, again, these different life paths are linked to general historical or personal life events. Finally, the active role of the person, in promoting both changes in self and context, has been indentified.

How should this book be characterized? First, it is a monograph on the principles of simple drawing: It takes the reader through those mechanisms and skills that characterize the performance of the child and adult who, without professional training, set out to draw or copy simple (and occasionally not so simple) objects and designs. Second, it is basically empirical rather than theoretical or speculative. It is based on the documentation not only of products, but of processes of production, using video recording and systematic analysis of structure and detail. Third, the philosophy is rationalist. That is, it attempts wherever possible to use the sense of why things are done the way they are. I believe we should be most suspicious of the concept of the convention, and in particular the “arbitrary convention” as an explanation of action. Even when drawers fail abysmally to achieve their goals, their efforts are usually orderly and purposeful at many levels.

A note about the characteristics of the subjects. They were all volunteers (or in the case of the small children, were volunteered), and in either case deserve my thanks. Almost all the subjects, with the exception of a group of English left-handers studied in Cambridge (through the good offices of the Cambridge Public Library) and some people whose native scripts and calligraphy were studied (Chinese, Thai, Burmese, Arabic, Hebrew), were part of the Australian population, more specifically the Sydney population.

In an earlier chapter I described how unquestioning (and obliging) both adults and children are when they are asked to produce drawings. They fulfill the request much as they would add a column of figures put before them or type “The quick brown fox. …” By contrast, if you ask them to provide a recipe, tell a joke, name a hotel, or describe their feelings, all but the most acquiescent will ask for the pretext. There are two reasons: Knowing the task in hand helps them to frame their response, but more important, in everyday life these pieces of behavior are not identified as pedagogical performances but social acts, and to produce them without a motive is anomalous.

Drawing in everyday life

In this final chapter I wish to take drawing out of the investigative-pedagogical frame and to ask three questions: (1) What sorts of functions do drawings serve for the ordinary person in a middle-class Western urban setting? In language, one refers to “speech acts” (Austin, 1962; Searle, 1969), and there is no reason why we should not try to identify “graphic acts.” (2) How is the graphic act embedded in ongoing affairs: Does it typically appear by itself, or is it usually part of a broader action that includes speech, gesture, and so on? (3) Finally, how is the execution of the graphic performance affected by its social function and by its integration into a broader communicative scenario?

“The multi-storied edifice”

One of the classical distinctions in the study of language has been that between its syntagmatic, or horizontal, organization and its paradigmatic, or vertical, structure. The syntagmatic dimension emphasizes the sequential structure of language forms. Its parallel in graphics is the sequence of production. The paradigmatic dimension of language deals with the fact that at any point in the sequence there is available a range of units or segments, the prototypical instance being the choice of word (“I,” “you,” “she”; “give,” “take”; “at,” “to,” “from”). In drawing we deal with the paradigmatic dimension when, for example, we consider which of a range of standard primitives (lines, circles, dots) are used in portraying parts of an object.

There is, however, another way of viewing the organization of these two systems, which is to consider language and graphics as layered systems wherein each action is or can be simultaneously structured or constrained at a great variety of levels. Hence the sound stream of speech carries multiple layers of organization, from the most biologically fixed qualities of the voice through all the phonological, syntactic, semantic, and pragmatic levels. If we choose the convenient starting point in language of the word, we can work down into its phonology, morphology, stress, tempo, the various stable and transient qualities of the voice used in its production; and we can work upward to its function in phrase, clause, sentence, its place in discourse, its social purpose, its multiple social contexts, its relation to gesture and other action.

Chapter 1 revealed that particular actions can often be shown by analysis to be special cases of more general principles of action. For example, a right-to-left horizontal movement or a top-to-bottom vertical movement can be located within a spectrum of preferred stroke directions, and may not in such a context be of special significance. And certain features of action that seem at first to be unified can be shown to be functionally differentiable – for example, fanning movements may be distinguished from finger flexion movements, and starting position can be shown to have different properties from stroke preferences. Third, the analysis may simply be descriptive, or it can be pursued to the practical logic that makes sense of the generalities and distinctions. I cannot promise that the analysis of the production of curvilinear forms will clarify all the issues, but it does have some of the features I have reviewed: There are some useful general principles and one or two unexpected disjunctions in the data, and I have tried to make sense of the concrete underpinnings of the structure that emerges.

The drawing of arcs

Geometrically we define arcs as portions of circles, and so it is somewhat surprising to discover that arc production is not only divergent from circle production, but is in fact quite its antithesis. I have analyzed the production of arcs of two lengths: 90 degrees (quarter circles) and 180 degrees (half circles).

There are two ways in which to draw a simple horizontal line – from left to right and from right to left. When lines are combined together in closed figures such as triangles, rectangles, and rhombuses, the number of possible construction sequences rises steeply. For example, if we ignore whether or not the drawing instrument is raised from the paper at the corners, there are 48 ways to draw a triangle; if we include the option of raising the pencil, the number of possible courses of action rises to 192. The corresponding values for quadrilaterals are much higher.

There is, furthermore, a great variety of proportions and orientations of figures like triangles, so any attempt to provide a comprehensive formula for specifying how the figures are produced by subjects may seem unattainable. Fortunately subjects do not exploit more than a tiny fraction of the courses of action available, and the principles governing their approaches are quite general, so it is possible to utilize the same methods of analysis and emerge with the same laws not only across all types of triangles in all their orientations, but across all other rectilinear figures, including solids.

The analysis of plane figures

The original attack on the problem was to collect copying performances on a great variety of abstract forms exploiting differences not only in basic geometry and orientation, but in the type of line used (plain, interrupted, oscillating) and the various combinations of forms – concentric, overlapping, and so on.

The study I am about to report shows that what a drawing represents can affect the strategy of its production; final execution is not by any means monopolized by the formal geometric aspects of making lines on paper. To give a simple example, an arrow pointing to the left is, geometrically, a horizontal line with a pair of shorter oblique lines running diagonally back from its left-hand end. Formal graphic constraints invite the right-handed drawer to make the major stroke from left to right, but its representational significance may promote the reverse, a stroke that moves in the direction the arrow points. This does not mean that geometric constraints become irrelevant. Rather, the drawer's action in any particular instance may result from cooperation or competition between the two forces, geometric and semantic. The context of drawing may modulate this interaction, biasing it in one direction or the other. The more the context emphasizes meaning and the less routinized it is, the more likely it is that semantics will prevail over geometry at the point of action, should they be opposed.

Drawing and speech

Before outlining an analysis and demonstration of this interplay in drawing and copying, I should like to compare the structure of drawing and speech production from this point of view. On the whole, semantics and pragmatics do not intrude on mainstream executive processes in speech.

In the analysis of spoken language, it is a commonplace to distinguish between the literal meaning of what is said and the intention or the “sense.” The first comprises the domain of semantics, the second the domain of pragmatics. If we apply this categorization to drawing, we might say that the analysis of how people represent objects and events they have been asked to portray lies squarely within the semantics of drawing. As we will see, however, one is obliged to conduct any inquiry into semantics with an eye on both the impact of formal executive processes and the social context of the drawing act, matters that are not themselves semantic.

The drawing task and its social setting

The task given to adult subjects in this investigation was simply to draw common objects. The 25 subjects were university undergraduates and junior staff of the psychology department who drew among them 100 common objects. Each subject was given a booklet of A4 paper, each page of which was divided into quadrants with a title typed in each: “ball,” “bell,” “belt,” “bow tie,” and so on. Each group drew a little over 50 objects.

Before describing some of the features of their drawings, I should like to comment on the broader context of the task, since the outcome cannot properly be understood simply in terms of the narrow specification of materials and instructions.

Paper contact

When subjects reproduce simple geometric forms, the majority of strokes conform to the preferred stroke direction. One important source of exceptions arises from a tendency to keep contact with the paper as the pencil moves from one linear element to another. Subjects not uncommonly turn a corner without lifting off and may then be compelled to proceed in a normally nonpreferred direction. This practice is sometimes called threading, and is of course the factor that in writing distinguishes cursive script from lettering. We have seen that such stroke continuity has been a significant force in script evolution, and accounts for the very fundamental difference between the execution of Hebrew and Arabic script.

Before I describe some of the factors that favor or discourage continued paper contact, it should be noted that the medium we used does not itself limit continuity. When traditional draftspeople used pens and brushes that needed continual replenishment with ink, there was an upper limit on stroke length that had to be integrated into the structure of the drawing performance. Since all our subjects worked with pencil or nylon-tipped pens, this was not an issue.

The analysis of a large number of rectilinear figures shows that drawers are very systematic in determining whether they will lift off or continue. If they have not continued around a corner, it is because they are going to relocate at another point on the figure.