Developmental psychology as a field has undergone many theoretical changes, and concomitant with those changes has been the introduction or redefinition of such terms as development, adult-development, aging, life-span, life-course, and life-cycle. While some consensus exists concerning the usage of each term, this consensus in not always universal. This lack of agreement is in part due to differences in theoretical perspective and to differences in the disciplinary fields from which they originated. As a result, some terms are misused. In fact, some terms are used interchangeably although not all theorists would agree that this is appropriate. For example, life-span and life-course are often used interchangeably, however, by definition, they have different meanings. This lack of explicitness within the field thus serves as a possible source of confusion, both methodologically and theoretically. For the purpose of this paper, each term will be defined and contrasted with the other terms. This will include a statement concerning the consistency of use for each term.
Of the terms listed above, development has the widest range of definitions. This is in part due to the usage of the term development by a wide range of disciplinary fields, and its roots both in philosophy and science (Groffmann, 1970). The narrowest definition is that offered by biologists: "Development is the progressive production of he phenotypic characteristics of an organism through the process of cellular differentiation, morphogenesis, and growth" (Levy, 1978, p. 525). In other words, development for the biologist is the progressive growth of the human organism from conception to maturity. Maturity being defined as an achieved steady state for size, form, and functioning of the organism. At this point, according to biologists, aging begins. It should be noted that this definition of development has a teleological connotation; it is based on the belief that development and evolution represent progress. Thus, aging, according to a biological definition, would not constitute a period of development.
This definition can be contrasted with that proposed by life-span developmental psychologists: "Development is a life-long process beginning at conception and ending at death" (Honzik, 1984, p. 309). Development is thus extended to include the whole of life. Development is seen not only as a biological process that ends at maturity but as a psychological process that continues throughout the life-span. As Buhler (1968) argues, certain aspects of psychological development can take place independent of ones biology. For example, one can be creative intellectually while experiencing physical deterioration. Biology and psychology are not necessarily tied together. In addition, Baltes et al. (1980) argue that even events such as impending death can be viewed as important developmental processes. For example, the life review process (Butler, 1963) can be defined as an important developmental task of later adulthood. Thus, life-span developmental psychologists take a broader view as to the definition of development.
It should be noted that what is termed development by biologists is often termed maturation by psychologists. Craig (1986) defines maturation as "the physical development of an organism as it fulfills its genetic potential" (p. 9). Biological changes that occur beyond maturity are defined as aging. Thus, biologists and psychologists do not necessarily disagree, but there is some confusion over terminology.
The term development can further be influenced by ones1s world view. Thus, someone operating from an organismic world view would see development as progressive and cumulative resulting from or correlated with structural change (Reese & Overton, 1970). In addition, these individuals would view the term development as primarily theoretical. This can be contrasted with someone operating from a mechanistic world view. For them, change is quantitative and multidirectional (Reese & Overton, 1970). The term development is viewed as primarily descriptive. Therefore, one's paradigmatic or world view affects one1s definition of the term development.
Adult development can be defined as a term or as a field of study. By far the most common and consistent usage is as the later. As a field of study, adult development refers to the study of early and middle adulthood; later adulthood usually falls under the fields entitled aging or gerontology. How one approaches the study of adult development, however, depends on one's theoretical orientation, and how one subsequently defines the term adult development. Therefore, a structuralist would approach the study of adult development much differently that a life-span developmental psychologist. For example, Levinson (1986), as a structuralist asks questions such as: "how can we make bet use of the distinction between hierarchical levels and seasons of development?" and "Are there age-linked developmental limitations of adulthood?" (p. 9). Conversely, Baltes et al. (1980), a life-span developmental psychologists, state that "the periods of adulthood and old age represent extreme testing grounds for a life-span developmental posture, at least with regard to the long-term impact of infancy, childhood, and adolescence on subsequent development during the life-course" (p. 97). Thus, each defines the appropriate course of study within adult development by their respective theoretical orientation.
In addition to there being little consistency as to how to study adult development, there is little consistency as to the use of adult development as a term. This is primarily due to ones usage of the term being influenced by one1s theoretical orientation or world view. For example, Levinson (1986) defines adult development as "the evolution of the life structure in early and middle adulthood" (p. 3). This exemplifies Levinson's structuralist viewpoint. Therefore, for one to understand how the term adult development is being used, one needs to know the orientation of the individual using it.
Aging can also be defined as a term or as a field of study. As a field of study, aging refers to the period also known as later adulthood. In this regard, the usage of aging to describe a field of study is fairly consistent. As a term, however, one will find aging primarily defined in one of two ways. First, aging is seen as an aggregate of biological change beyond the point of optimal maturity (Buhler, 1968; Craig, 1986). There is some consistency of usage between biologists and psychologists with this definition of the term aging. However, this definition of aging is often associated with decline (Birren, 1964). Thus, life-span developmental psychologists have proposed an alternate position. Kermis (1984) states that "the psychology of aging, geropsychology, focuses on the behavior of individuals involved in the processes of postmaturity development" (p. 5). This definition places an emphasis on continued development in old age as opposed to a decline in functioning. It proposes that aging is not a disease but rather a normal developmental process.
Perhaps some of the confusion or disagreement, concerning the term aging, could be alleviated if it were recognized that aging is not a unidimensional concept. Aging can occur on at least three dimensions: chronological aging, biological-physiological aging, and psycho-social aging (Kermis, 1984). In terms of chronological aging, all individuals are aging. It is a time based dimension. Traxler (1980) discusses the myth of the dominance of chronological aging. According to Traxler, our society defines age almost entirely in terms of chronological years as opposed to functionally. Traxler states, "To characterize older persons simply on the basis of their chronological age is a terrible injustice and totally ignores the tremendous heterogeneity and diversity displayed by the elderly" (p. 11). Thus, chronological aging, while the easiest to catalog, is the least useful of the dimensions listed above. Biological aging is the point at which development (biological definition) has ceased. Subsequent change is usually seen as decline or deterioration. This definition is closely aligned to the definition of aging as an aggregate of biological change beyond the point of optimal maturity (Buhler, 1968; Craig, 1986). Thus, while this definition is widely used, it might best be restricted to the biological realm. Psycho-social aging refers to the psychological and social development of the individual. In other words, psycho-social aging is a normal, integral part of the life span and is characterized by continued growth and development as opposed to decline and deterioration. It is this facet of aging that most interests life-span developmental psychologists.
The term life-span in its simplest form can be used to describe the period between conception and death. However, life-span is often used in conjunction with the term development to form life-span development, and as such the usage is different. Life-span development can not, however, be defined as a distinct theoretical position or term but rather as an approach or orientation to the study of human development (Baltes et al., 1980; Baltes, Reese, & Nesselroade, 1977). It should be noted that the life-span developmental approach has much in common with the contextual world view.
There are two basic premises to the life-span developmental approach. First, the life-span perspective maintains that development occurs at all points across the life-span (Baltes et al., 1980; Baltes et al., 1977; Honzik, 1984). Thus, development is not limited to prematurational processes but extended to postmaturational processes as well. Second, development is seen as being influenced by the past (what has gone on before) and the future (what is expected or perceived to come) of the individual (Baltes et al., 1980; Baltes et al., 1977; Honzik, 1984). This premise is important as life-span developmental work should not be equated with age-developmental work; chronological age should not be used as the only organizing variable for the study of life-span development (Baltes, 1979).
Hultsch and Deutsch (1981) offer the following description of the life-span developmental approach: "The life-span developmental approach is concerned with the description, explanation, and optimization of intraindividual changes in behavior, and interindividual differences in such changes in behavior from conception to death" (p. 15). This definition can be examined to further delineate what is meant by the life-span developmental approach.
First, life-span developmental psychologists concern themselves with three tasks: description, explanation, and optimization (Baltes et al., 1980; Hultsch & Deutsch, 1981). The description task looks at what is changing and when is it changing. For example, is change multidirectional or unidirectional? Is it continuous or discontinuous? Examination of cohorts or life transitions would also be examples of descriptive tasks. The explanation task looks at why change is occurring. This task would involve examining the interactive relationship of the individual and the environment. A study of normative age-graded, normative history-graded, and nonnormative life-event influences would also be included as an explanation task. The optimization task looks at how change can be optimized or how behavior can be changed. This task would include remediation, intervention, prevention, and enrichment (Baltes & Danish, 1980).
Second, the definition emphasizes behavior-change as opposed to age-change. Thus, the life-span developmental approach is not tied to examining behavior only as it relates to a particular age. Rather, age is used as a descriptive variable.
Third, the life-span developmental approach concerns itself with interindividual differences in intraindividual change. In other words, the life-span approach looks not only at behavior-change within the individual over time (within-person change), but, also, how individuals differ in such changes (between-person change). For example, we could study an individual1s psycho-social development over time. For that individuals there may be a steady rate of development or it could ebb and flow. Conversely, we could examine how that individuals development is different from other individuals. This would constitute interindividual differences in intraindividual change (Hultsch & Deutsch, 1981).
Finally, according to the life-span developmental perspective, development occurs from conception to death. Thus, one not only develops prenatally, in childhood, and in adolescence but throughout the entirety of one's life.
Other features associated with life-span developmental perspective not included in the definition provided by Hultsch and Deutsch (1981) include the concepts of embeddedness; normative age-graded influences, normative history-graded influences, and nonnormative events; and the impact of one's perception of the future on development. These argue that one's development can not be separated from one's context. An individual life is inextricably interwoven into the fabric of their context including past, present, and perceived future.
The usage of life-span development is fairly consistent. As noted, however, life-span development refers not so much to a specific term but rather to an orientation or approach to the study of human behavior.
The terms life-span and life course are often used interchangeably. However, this is not appropriate as they do not refer to the same underlying concept (Hagestad & Neugarten, 1985). The term life course is traditionally used by sociologists, and refers to the interaction of the environment and the person; it is a distinctly social concept (Maddox & Campbell, 1985). Conversely, when psychologists speak of life-span development, they are traditionally focusing on intrapsychic phenomena (Hagestad & Neugarten, 1985).
The term life course has its roots in anthropology, specifically, ethnographic studies on age-grading (Hagestad & Neugarten, 1985). Anthropologists have examined how societies created age-related transitions and how these transitions have given meaning to the individual as they passed through their lives. It is through this analysis that the concept of life course was originally derived.
Levinson (1986) defines life course as the "concrete character of a life in its evolution from beginning to end" (p. 3). According to Levinson, both words in the term life course need to be looked at carefully. The first word in the term life course is life. Levinson states that the word life "must include all aspects of living" (p. 4). Thus, life includes biological changes, social relationships, intrapsychic phenomena, ones relationship to the environment; everything that is significant to the individual. In other words, when conducting a life course analysis (Riley, cited in Maddox & Campbell, 1985), all aspects of the individual's life must be studied, whether it be work, family, aspiration, fantasies, etc. In addition, all the interactions and interweavings of these component parts of an individual1s life must be examined. Finally, an individual's life is not static thus one must look at the evolution of these patterns and interweavings over time. Only by looking at the whole of an individual's life can one come to understand the character of that life.
The second part of the term is the word course. The word course, according to Levinson (1986), "indicates sequence, temporal flow, the need to study a life as it unfolds over the years" (p. 3). To be able to study this sequence or flow, one must not look at an isolated point in time or points in time. For example, longitudinal research is not an application of a life course analysis. The word course indicates that one must look at the process involved in and underlying the temporal flow; the evolution of an individual's life. It should be noted that this sequence may not be stable or continuous, rather at times it may exemplify change and discontinuity. This must be take into account studying individuals from a life course perspective.
The major problem with the term life course is that methodologically it is difficult to accomplish. For example, the field of developmental psychology usually examines development one of two ways. Development is either studied chronologically or by developmental area. In other words, one studies childhood or adolescence. This would be an example of studying development chronologically. Conversely, one could also study moral development or personality development. This fractionalization of the individual is contrary to what is meant by the term life course. Thus, the study of life course is difficult methodologically.
The term life-cycle is another term commonly used within the field of developmental psychology. It is often and incorrectly used interchangeably with the terms life-span and life course. The term life cycle is defined as the underlying order of the human life course (Buhler, 1968; Levinson, 1986; Linden & Courtney, 1952; Neugarten & Datan, 1973). In other words, there is a universal sequencing to individual's lives. This view of the human life cycle is exemplifies by Shakespeare's seasons of man and Erikson1s psychosocial stages (Erikson, 1982). Thus, the study of the life cycle could further be described as being concerned with normative age-graded influences.
For those involved in the study of the life cycle, there is relative consensus over the definition of the term life cycle. However, there is little consensus over how the individual life cycle can be described. Levinson (1986), for example, describes a macrostructure of the life cycle. This macrostructure is composed of "eras" and "cross-era transitions". Essentially, according to Levinson, the life cycle is chronologically composed of: preadulthood (conception - age 22), early adult transition (age 17 - age 22), early adulthood (age 17 - age 45), midlife transition (age 40 - age 45), middle adulthood (age 40 - age 65), late adulthood transition (age 60 - 65), and late adulthood (age 60 - death). Thus, Levinson proposes a very specific age-dependent conception of the life cycle. This can be contrasted with the life cycle theory outlined by Linden and Courtney (1979). Linden and Courtney propose that he life cycle can be only divided into three periods: evolescence (the period ending in young adulthood), senescence (middle and later adulthood), and senility (the decline of the individual in old age). Associated with each of these periods is a set of ordered achievements which are hypothesized to normally occur. For example, during evolescence, the achievements include social learning, instinctual supremacy, and mating/reproduction. Thus, while this theory can be chronologically ordered, it is not an age-dependent perspective but rather an achievement oriented perspective of the life cycle. It is clear from these two examples that while theorists may agree that an underlying order to the human life course exists, there is little agreement over what constitutes the component parts of the life cycle.
Neugarten and Datan (1973) propose that there are three dimensions of time that must be addressed when examining the human life cycle. The first two time dimensions described by Neugarten and Datan are life time and social time. Life time is essentially chronological time as one moves through the life cycle. It should be noted that life time does not necessarily determine age status. For example, an individual may be defined as an adult in one culture but not in another. Social time is composed of age-graded norms for behavior. As such, social time is culturally defined. Life time and social time are not synchronous. Rather, it is the interaction of the two dimensions that generate meaning. For example, the meanings change if one is describing a pregnant woman who is age 13, 25, or 50. Therefore, the discrepancies between theorists may in part be due to the lack of acknowledgement concerning these two time dimensions.
A third dimension is also proposed by Neugarten and Datan (1973) - historic time. Historic time can be described as the political, economic and social environments affect on the life cycle. As these environments change they affect the life cycle. For example, as the population of the United states ages, it is proposed to go from a youth oriented society to one involved actively in issues of middle and later adulthood (Neugarten & Datan, 1973). Thus, historic time must also be taken into account when describing the life cycle.
The time dimensions outlined by Neugarten and Datan (1973) are not static; they are in a state of constant change and continuous interaction. Thus, it would be difficult to propose a universal theory of the life cycle. This may in part explain the theoretical discrepancies between life cycle theorists.
To summarize, the terms development, adult development, aging, life-span, life course, and life cycle are currently widely used within the field of developmental psychology. The term development has the widest range of usage, extending from a narrow biological definition to a life-span developmental definition. How one defines development largely depends on one's paradigmatic and world view. Therefore, the use of the term development is only moderately consistent.
Adult development can be defined as a term or field of study. Similar to the term development, how one defines adult development is dependent on one's paradigmatic and world view. As a field of study, it refers to the study of early and middle adulthood. How one studies or researches adult development is, once again, dependent on one's paradigmatic and world view. Therefore, the use of the term adult development is only moderately consistent.
Aging can also be defined as a term or field of study. As a term, aging can be defined as either, the point beyond optimal maturity, a period of postmaturational development, or be broken down into a multidimensional concept (chronological, biological, and psycho-social aging). Thus, there is only moderate consistency of the use of aging as a term. As a field of study it refers to the period of later adulthood.
The terms life-span, life course, and life cycle are often used interchangeably and incorrectly. Despite the inconsistency of use, there is some consensus over how they should be used or defined. As a term, life-span refers to the span of life from conception to death. Life-span development, however, refers to an approach to the study of development. As an approach to the study of development, life-span development proposes that development occurs across all points of the life-span and is influenced by the past, present, and future.
Life course refers to the evolution of an individual's life, including all that is significant to that individual. The term life course places an emphasis on the interaction of the individual and their social environment.
The term life cycle is defined as the underlying order of the human life course. While the definition of the term life cycle is relatively consistent between theorist, there is little consensus concerning how the life cycle can be described.
The best usage of each term is influenced by one's theoretical orientation. For example, the life-span developmental approach view development as a life-long process, and adult development as the study of that process during the early and middle adult years. In addition, aging is viewed as a tripartite concept which includes biological, chronological, and psychosocial aging. The later defined as postmaturational development. Therefore, to understand another's usage of a particular term, one must be aware of the other's theoretical orientation.
1998 copyright Linda M. Woolf
To the next section of the paper. A description of the methodological problems and proposed solutions associated with the fact that the psychology of aging must deal with age-graded, history-graded, and non-normative influences as well as with the so-called terminal decline.
Back to the Introduction.