The article below is a follow-up to Willis F. Overton's "Relationism and Relational Developmental Systems: A Paradigm for Developmental Science in the Post-Cartesian Era" and Peter J. Marshall's "Beyond Different Levels: Embodiment and the Developmental System," (which is a more recent piece than the one below, but the one below is more in-depth).
This another installment in my continuing fascination with Relational Developmental Systems and its application in both psychology and epigenetics.
Marshall, PJ. (2013). Coping with complexity: Developmental systems and multilevel analyses in developmental psychopathology. Development and Psychopathology; 25(4, pt 2): 1311–1324. doi:10.1017/S0954579413000631
Coping with complexity: Developmental systems and multilevel analyses in developmental psychopathology
PETER J. MARSHALL
Developmental psychopathology is not characterized by adherence to one specific theory but instead serves as an organizational framework in which research is driven by a number of key assumptions. In the developmental psychopathology approach, two primary assumptions emphasize the importance of systems thinking and the utility of multilevel analyses. As will be illustrated here, these emphases are inextricably linked: a systems approach necessitates a multilevel approach, such that a level of organization must bring coherence to a level of mechanisms.Given this assumption, coming to an integrative understanding of the relation between levels is of central importance. One broad framework for this endeavor is relational developmental systems, which has been proposed by certain theorists as a new paradigm for developmental science. The implications of embracing this framework include the potential to connect developmental psychopathology with other approaches that emphasize systems thinking and that take an integrative perspective on the problem of levels of analysis.
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Among the foundational emphases of developmental psychopathology are the necessity of a systems approach and the value of explanations that bridge multiple levels of analysis (Cicchetti, 2010; Sroufe & Rutter, 1984). Both of these emphases have played a significant role in the success of the developmental psychopathology approach by framing the understanding of adaptation and maladaptation across the life span. Accordingly, most contemporary developmental psychopathologists would view themselves as subscribers to some form of systems approach (e.g., as espoused by Cicchetti & Toth, 1997; Sameroff, 2000), and the encouragement and use of multilevel analyses remains a key theme (Burnette & Cicchetti, 2012; Cicchetti, 2008, 2011; Cicchetti & Curtis, 2007). It may therefore be objected that in undertaking a discussion of these familiar constructs I am preaching to the converted. However, my suggestion is that the 25th anniversary of the first volume of Development and Psychopathology presents an opportunity not only to reiterate the theoretical importance of systems thinking and multilevel analyses but also to consider the changing background for these emphases as we look ahead to the next 25 years.
The initial focus of this article concerns the influence of embryology and developmental biology on the systems approach in developmental science more generally and on developmental psychopathology more specifically. Although much of the original impetus for systems thinking came from classic work in embryology, recent advances in developmental and evolutionary biology have further underscored the necessity of a systems approach. These advances are illustrating the vast complexity involved in the construction of a phenotype, and they are putting a great deal of pressure on traditional approaches to conceptualizing the interplay of biology and environment in understanding developmental processes. With its status as an inherently integrative discipline, developmental psychopathology promises to be an important testing ground for these issues as we head into the next decades of the discipline.
One key premise of the current paper is that a systems approach and the need for multiple levels of analysis go hand in hand. This premise is based on the assumption that a systems approach requires the consideration of two types of explanations that can be seen as occupying different levels of analysis: a level of organization (i.e., a systems level) that serves to bring intelligibility to a different level of mechanisms. This key tenet is manifested in the central principle of organicism, which stipulates that mechanisms (i.e., the parts of a system) can only make sense in the context of a holistic systems level that, in turn, cannot be reduced to its parts (Pepper, 1942; von Bertalanffy, 1968).
Given the necessity of multiple levels of analysis, conceptualizing the relations between these levels becomes of utmost importance. Overton (2006, 2010) has written extensively on the contrast between a Cartesian worldview that imposes a “split,” or separation between levels, and a relational worldview that emphasizes their interdependence. A worldview constitutes a broad metatheoretical framework “that both describes and prescribes what is meaningful and meaningless, acceptable and unacceptable, central and peripheral, as theory . . . and method . . . in a scientific discipline” (Overton, 2007, p. 154). As described by Overton (2013), the split and relational worldviews give rise to different “midrange metatheories,” which in turn provide meaning contexts for more specific theoretical constructs. One such midrange metatheory that arises from the relational worldview is that of relational developmental systems, which Lerner and Overton have suggested provides a paradigm for the future of developmental science (Lerner, 2006; Lerner & Overton, 2008; Overton, 2006, 2010, 2013). As such, the relational developmental systems approach recognizes the dynamic complexity of developmental processes and exposes the inadequacy of split approaches, which emphasize simple interaction and the elevation of one level of analysis over another.
One goal of the current article is to explore the potential role for the relational developmental systems approach in maintaining the vitality of the study of adaptation and maladaptation in human development. To begin this exploration, I will first step back and briefly trace biological influences on systems thinking in developmental psychopathology. This tracing then leads to a discussion of the concept of the developmental system, its deep connections with developmental and evolutionary biology, and its place in the broader relational paradigm as formulated by Overton and Lerner (2012). This relational aspect is then more fully elaborated through an exploration of multiple levels of analysis.
Systems Approaches in Developmental Psychopathology: Biological Influences
As documented by Cicchetti (1990, 2010), the systems emphasis in developmental psychopathology has its origins in principles derived from the embryological studies of Kuo (1939), Spemann (1938), Waddington (1957), and Weiss (1939), among others. Key emphases from the classic work in embryology include the hierarchical nature of development, principles through which more complex forms arise from simpler ones, and the importance of context in early development. In turn, one even earlier influence was that of von Baer (1828/1956), who used his own findings concerning embryological development to formulate general principles of developmental change, particularly the concept of development as a continuing process of differentiation and integration.
One reason for the foundational quality of the classic work in 20th century embryology was that it was characterized by an organicist perspective that emphasized the emergent properties of higher level systems. Organicism is closely connected to the notions that parts of a system can only be understood through their relation to the whole system and that the behavior of a system cannot be predicted from, or reduced to, the simple aggregation of its parts (Pepper, 1942). Among other biological influences, the organicist perspective had received particular support from the embryological work of Spemann (1938), whose seminal findings with Mangold had highlighted the importance of plasticity, constraints, and context in early development (Mangold & Spemann, 1924, 2001).
Within developmental psychology, the influence of the organicist perspective in embryology was manifested in various ways (Cairns & Cairns, 2006; Sameroff, 1983). For instance, the orthogenetic principle of Werner (1948) and Piaget’s (1977) concept of equilibration were partly formulated with reference to evidence about the generation of novelty from the study of embryological development. More recently, Gottlieb (1992, 1998, 2007) drew on research in embryology (including his own) in delineating the theory of probabilistic epigenesis, which stands as an example of a biologically inspired systems approach that has also been specifically applied to the area of developmental psychopathology (Gottlieb & Willoughby, 2006). Probabilistic epigenesis is fundamentally an organicist, holist theory that emphasizes the interconnected nature of the parts of the developmental system. From this perspective, conceptualizing these connections goes beyond simple notions of interaction to a more dynamic set of reciprocal, bidirectional, coacting, interpenetrating processes (Overton, 2013).
Related to its influence on developmental psychopathology, Gottlieb’s seminal work played a formative role for a particular systems approach that is rooted in biology and that has been labeled developmental systems theory (DST). Here I wish to explore the contention that a broader extension of this approach, that of relational DST, can provide a potentially fruitful organizing framework for developmental science (Overton & Lerner, 2012). As a product of the relational worldview, this framework has at its core the related concepts of the developmental system and multiple levels of analysis (Overton, 2013). In this sense there is a distinct alignment between relational developmental systems and core tenets of the developmental psychopathology approach. However, noting this basic alignment is not enough for us to realize the transformative implications of the relational approach for developmental psychopathology. In order for that to take place, we also need to appreciate how the broader relational approach informs more specific, lower level theoretical approaches and how such approaches can inform empirical work in developmental psychopathology. As an initial step in this direction,we can now turn to the biologically inspired approach of DST as one such approach, and we can then consider how its extension through a broader relational aspect can expand the purview of this approach to the study of human adaptation and maladaptation across the life span.
In the early 1990s, the term DST was introduced in two separate contexts and disciplines: by the developmental psychologists Ford and Lerner (1992) and then by two philosophers of biology, Griffiths and Gray (1994). Both sets of authors drew on the work of Gottlieb and other theorists (e.g., Lehrman, 1970; Oyama, 1985) who emphasized the importance of a systems perspective in the study of developmental processes. For current purposes, I will overlook differences between specific approaches (see Keller, 2005) and will simply introduce the core tenets of DST as a biologically oriented theory.
For proponents of DST, the explanandum (what is to be explained) is how the individual organism becomes constructed, and the explanans (the explanation) is the entire developmental system itself, which includes all biological and environmental resources available to the organism. This emphasis relates to the parity thesis of DST, which does not allow any one aspect of the developmental system to take an elevated causal role (Griffiths & Knight, 1998). From this perspective, parts of the developmental system derive their meaning from the context of the entire system, and the elevation of one developmental resource over another makes little sense (for a discussion, see Shea, 2011). This thesis gives rise to a fundamental tenet of DST, which is a strong objection to explanations of development that privilege the role of genes (see e.g., Ford & Lerner, 1992; Griffiths & Gray, 1994; Keller, 2010, 2011; Lerner, 2006; Lickliter & Honeycutt, 2003; Oyama, Griffiths, & Gray, 2001; Robert, 2004). Although DST theorists would acknowledge that the presence of genetic material is a necessary condition for cellular function, they emphasize that genes are not unmoved movers in that they only become causally relevant through their involvement in the entire developmental system.
In denying a privileged developmental role for genes, DST is diametrically opposed to any suggestion that DNA contains the information needed to construct an organism. The notion of a “genetic blueprint” has been the focus of intense criticism from a variety of developmental systems theorists (Ho, 2010; Jablonka & Lamb, 2005; Lerner, 2006). This criticism has arisen through recent developments in biology that have challenged traditional notions of genetics (Charney, 2012) and evolution (Ho, 2010; Jablonka & Lamb, 2005). These developments have included advances in epigenetics (Meaney, 2010) and the way in which the genome is conceptualized (Keller, 2011) as well as the converging appreciation that what is inherited by an individual organism is not only a complement of genes but also the biological and environmental scaffolding of the developmental system (Griffiths & Gray, 1994; Ho, 2010; Jablonka & Lamb, 2005). Although a full discussion of these issues cannot be entered into here, they hold a great deal of importance for developmental science (Overton, 2013).
Today the gene-centric notion that the genome contains a blueprint for development, which ensures a direct relation between genotype and phenotype, is antithetical to most developmental scientists. However, it may still have some implicit appeal to those who are seeking ways to manage the complexity of development. To understand why, consider the suggestion of 17th century preformationists, aided by van Leeuwenhoek’s advances in microscopy, that fully formed miniature adults could be glimpsed within sperm or eggs. As ridiculous as it seems today, this suggestion makes sense when placed in its historical perspective. At the time, the alternative to preformationism was a form of vitalism in which mysterious, unknowable forces direct the appearance of form in the initially formless material of the egg (Gilbert&Sarkar, 2000). Gould (1977) suggested that, when seen in this way, preformationism can be understood as an attempt to copewith the daunting complexity of embryological development. Its allure was that vital forces did not need to be invoked to explain the biological world: if development was mainly a process of getting bigger, it could be more readily placed within the mechanistic worldview of Newtonian science. However, the glimpses of the preformationists turned out to be misplaced, and explicit mentions of preformationism are now mainly confined to introductory lecture courses as an illustration of a failed and naıve attempt to understand human development. However, echoing back more than 300 years, proponents of DST argue that the preformation–vitalism debate remains relevant to contemporary developmental science. In short, they see the mission of DST as countering preformationism in its modern guise of genetic determinism with DST as a nonvitalistic, scientific, epigenetic organicism (Godfrey-Smith, 2000; Robert, 2004).
The rejection of preformationism or a simplistic genetic determinism may seem trivial to those who already endorse a developmental psychopathology approach. More broadly, it could be argued that the genetic blueprint metaphor represents a straw argument that is not the purview of contemporary developmental science. Perhaps we could take a less deterministic perspective on genes, denying them a fully explanatory or causal role and relaxing the literal blueprint metaphor to a kind of looser plan. In this arrangement, we could still see genetic information as specifying a latent, but potentially modifiable, representation of a trait and allowing other influences to play potentially important roles in determining the phenotypic expression of that trait. However, part of the challenge presented by DST is that even this looser conceptualization is seen as problematic: it is here that the stronger claims of DST take the approach into what may be less comfortable territory for many (Stotz, 2008). At the heart of DST is the view that the developmental system as a whole cannot be partitioned or split apart without a fundamental loss of intelligibility (Overton, 2007). Through its rejection of any such developmental dichotomy, DST stands in opposition to the notion that developmental outcomes are some combination of genetic and environmental influences (Oyama et al., 2001).
The oppositional stance of DST originally arose in part as a response to attempts by behavior geneticists to separate genetic and environmental influences into additive components (for a discussion, see Partridge, 2011). Although such attempts continue to be under distinct pressure from findings in developmental and evolutionary biology, Charney (2012) recently argued that they have not been replaced by an adequate paradigm that accounts for the immense complexity of how a phenotype is constructed. In response, Lerner and Overton (2012) suggest that the paradigm of relational developmental systems that combines DST with a broader relational worldview can provide such a framework. To support this contention, one can turn to a vast amount of work in developmental biology that has begun to unravel the complexities of developmental processes at the level of gene expression and regulation. Although the accommodation of these complexities is not possible from the Cartesian perspective of traditional behavior genetics, DST was itself founded on the acknowledgement and understanding of these complexities (Keller, 2010).
Lessons from developmental biology
A primary source of support for DST comes from ongoing work in developmental biology describing how spatial and temporal patterns of gene expression and regulation in the developing embryo relate to the development of bodily form (Gilbert, 2010). Although early work in this area suggested the existence of “master control genes” that direct the formation of certain morphological features (Gehring, 1998), it has become clear that such genes operate in a highly context-dependent fashion (Mikhailov, 2005). For instance, expression of the paired box gene 6 gene is essential for eye formation in species as diverse as fruit flies and humans, but only in the presence of other transcription factors that are also involved in pattern formation in the head region. In other parts of the body, expression of the same gene plays an important role in very different functions (e.g., the differentiation of the pancreas).
One key lesson from this work (much of which has been done in model organisms such as drosophila) is that there are no genes that specifically or solely determine major characteristics of bodily form, such as segments, eyes, or wings. The same could be said for all bodily structures, including the mammalian brain (Stiles, 2008). Similar principles also extend to the development of more abstract bodily characteristics, such as symmetry or polarity (e.g., of hands, limbs, or eyes), which are not predetermined, but instead arise through the organized activity of the system (Minelli, 2009). There are genes involved in the development of all these structures and characteristics, and changes to these genes, in specific temporal and spatial contexts, can impede or divert the typical course of development. However, morphology clearly arises not through a specific genetic plan but through the reciprocal coaction of component parts of the wider developmental system.
Another lesson from developmental biology is that genes are not simply switched on and off in a maturational or predetermined fashion, but rather gene expression and regulation operate in the context of a wider and highly intricate developmental system. In support of the original organicist work in embryology, the picture that has emerged from developmental biology is that construction of the organism proceeds through dynamic cellular and molecular coactions involving genes, but not directed by them (Gottlieb, 2007). Thus, what becomes crucial are the laws governing these coactions rather than the programmed expression of genes. Developmental biologists have begun to uncover the principles that govern embryological growth at a cellular and molecular level, including fate maps, induction, morphogenetic gradients, redundancy, pleiotropy, positive and negative feedback, and nonlinearity (Gilbert, 2010; Rudel & Sommer, 2003; Wolpert, 1994).
The above themes suggest how the organicist framework in embryology, which provided part of the foundation for the developmental psychopathology approach, has been further strengthened by more recent findings in developmental biology. It is worth noting that lessons for developmental psychopathology from contemporary developmental biology extend much further than this brief treatment allows (Cicchetti & Cannon, 1999; Cicchetti & Curtis, 2006). For instance, other connections have been made through the emergent subfield of evolutionary developmental biology, or what is commonly known as “evo-devo” (Hall, 1992). Through the consideration of evolutionary influences on life history development (Gilbert, 2001), aspects of evo-devo have served as the inspiration for recent work on phenotypic plasticity in relation to environmental circumstances and the consequences of this plasticity for adaptation and maladaptation across the life span (Ellis & Bjorklund, 2012). However, it could be argued that much of the field of evo-devo has neglected the lessons from DST concerning the extended nature of the developmental system and the implications of this extension for evolutionary theory (Robert, Hall, & Olson, 2001).
Another theme shared with developmental biology comes from the notion that the process by which a pattern is constructed cannot be deduced from the final pattern itself, but only from a serious consideration of development. This connects to the raison d’eˆtre of developmental psychopathology: that a disorder can only be meaningfully viewed through the lens of development (Cicchetti, 2010). This issue may be more familiar as the concept of equifinality, the observation that the same pattern can arise through different mechanisms, with only the study of development being able to shed light on what these mechanisms might be. What is particularly fascinating is how far this core developmental principle extends, from the development of the patterns of butterfly wings (Brunetti et al., 2001) to the development of psychopathology (Cicchetti & Rogosch, 1996).
Complexity in developmental systems: Finding a way forward
The findings gleaned from developmental biology (as modern day embryology) have provided important insights into development as an epigenetic process that proceeds through dynamic and reciprocal coactions among coding and noncoding DNA, transcription and translation factors, the cytoplasm, and the intra- and intercellular environments more generally. From this perspective, the function of a gene depends heavily on contextual factors, including its temporal and spatial coactions with other genes and gene products. Along these lines, there have been important changes in the definitions of what constitutes a gene and the genome as well as a reframing of the role of environmental influences on gene expression (Greenberg & Partridge, 2010; Jablonka & Lamb, 2005; Jablonka & Raz, 2009; Keller, 2011). These developments are very much in line with the core tenets of DST, which places the construct of the gene within the wider developmental system. These complexities are being increasingly recognized in terms of their implications both for developmental science more generally and developmental psychopathology more specifically (Grigorenko & Cicchetti, 2012; Rutter, 2012).
A related lesson can be seen in the realm of developmental disorders, where the appeal of a biologically oriented DST approach has been bolstered by the growing consensus that the original promise of the revolution in molecular psychiatric genetics has not been realized (Charney, 2012). For example, the hunt to isolate straightforward genetic effects in disorders such as autism and schizophrenia has been severely hampered by factors such as genetic heterogeneity, pleiotropic effects, de novo mutations, and polygenic inheritance (Wahlsten, 2012). This is not to imply that genetics is uninvolved in such disorders or that novel methodological combinations of genetic and neuroimaging methods cannot shed light on the development of psychiatric disorder (Addington & Rapoport, 2012). It is rather that the sheer complexity involved in the construction of a phenotype requires the adoption of revised sets of assumptions and principles that would essentially constitute a paradigm shift away from traditional approaches (Charney, 2012).
As noted earlier, acknowledging the complexity of development has long been a key aspect of DST, and in this sense it potentially provides a signpost for progress in developmental science. Taking this further, Overton and Lerner (2012) have suggested that the requisite paradigm shift can be achieved through the combination of DST with a broader relational worldview that emphases “co-acting, co-developing processes functioning according to the reciprocal causality entailed by complex positive and negative feedback loops” (Overton & Lerner, 2012, p. 376). However, to better understand what this approach entails, we need to look closely at the question of multiple levels, since the core of the relational developmental systems approach concerns a particular way of conceptualizing different levels of analysis and the relations between these levels.
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This work was supported by an award from the NIH (HD-68734) and by a Fellowship from the Center for Humanities at Temple University. This article is dedicated to Willis F. Overton on the occasion of his retirement from the Department of Psychology at Temple University. For more than four decades, Bill has espoused the value of the relational approach as a guiding framework for psychological science, with deep implications for the study of typical and atypical development. The influence of Bill’s thinking on my writing here is unmistakable, and I am very grateful for his mentorship and for his input on previous drafts.