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Beyond mental health: An evolutionary analysis of development under risky and supportive environmental conditions: An introduction to the special section

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  Beyond Mental Health: An Evolutionary Analysis of Development UnderRisky and Supportive Environmental Conditions:An Introduction to the Special Section Bruce J. Ellis University of Arizona David F. Bjorklund Florida Atlantic University Evolutionary approaches to behavior have increasingly captured the attention and imagination of academics and laypeople alike. One part of this trend has been the increasing influence of evolutionarytheory in developmental science. The articles in this special section of   Developmental Psychology attempt to demonstrate why an evolutionary analysis is needed to more fully understand the contexts andcontingencies of development. The 3 theoretical articles articulate the core evolutionary logic underlyingconditional adaptation (and maladaptation) to both stressful and supportive environmental conditionsover development. These theoretical articles are then followed by 9 empirical articles that test theseevolutionary-developmental theories and hypotheses. Finally, 6 commentaries evaluate the prospects,pitfalls, and implications of this body of work. Keywords:  evolutionary-developmental psychology, adaptive phenotypic plasticity, life history theory,differential susceptibility, developmental programming Adaptation is a central theme of many contemporary perspec-tives on child and adolescent development. These perspectives,including human ecology and developmental systems to name justtwo, highlight the ongoing processes by which young people get insync with the contexts and environments in which they live. Suchapproaches are well represented in the pages of   DevelopmentalPsychology . Research on another important form of adaptation,however, has been much less represented in the journal:  condi-tional adaptive mechanisms . The operation of these mechanismsreflects how natural selection has shaped the developing brain torespond to different environmental contexts—good and bad—inan evolutionarily adaptive manner. Theory and research on con-ditional adaptations are relevant to understanding children’s de-velopmental responses to not only high-risk environments, such asexposure to neglectful parenting or poverty, but to highly support-ive environments as well.The dominant scientific paradigm for explaining children’s ad- justment to high-risk environments could be referred to as the developmental psychopathology  model. Central to this model is theimplicit if not explicit assumption that high-risk environmentsadversely affect children’s well-being, promoting disturbances indevelopment, even if not clinical disorders per se (e.g., see Belsky,2008). This has led researchers to focus on the deleterious effectsof stressors in and around the home, neighborhood, and schoolenvironments on mental health outcomes, and especially risk of psychopathology. Dysfunctional behavior in childhood and ado-lescence is often seen as the natural consequence of exposure toharsh, unpredictable, or uncontrollable socioecological contexts.Accordingly, the developmental psychopathology model empha-sizes the costs and largely ignores any benefits of children’sresponses to risky environments, making it difficult to explainchildren’s and adolescents’ motives for their behavior. This has ledmany developmental psychologists to view these responses (e.g.,externalizing behavior in childhood, reckless behavior in adoles-cence) as problems in need of a solution.An evolutionary-developmental perspective challenges this pre-vailing viewpoint. Because both stressful and supportive rearingenvironments have always been part of the human experience,developmental systems have been shaped by natural selection torespond adaptively to both putatively “positive” and “negative”developmental contexts. When children encounter stressful envi-ronments, therefore, it does not so much disturb their developmentas direct or regulate it toward strategies that are adaptive understressful conditions—even if those strategies are currently harmfulin terms of the long-term welfare of the individual or society as awhole. Conversely, when children encounter well resourced andsupportive environments, it directs or regulates development to-ward strategies that are adaptive in those contexts (Ellis, Boyce,Belsky, Bakermans-Kranenburg, & Van IJzendoorn, 2011). Thesearguments are presented in detail in the lead article of the specialsection (Ellis et al., 2012).For example, children’s brains and bodies tend to respond todangerous or unpredictable environments by growing up fast andliving for the here and now. This “get it while you can” strategyoften translates into behaviors in adolescence such as violentcompetition for status and respect, breaking rules and laws, con-  Editor’s Note.  Jacquelynne S. Eccles served as the action editor forthis article.—JSEBruce J. Ellis, John and Doris Norton School of Family and ConsumerSciences, University of Arizona; David F. Bjorklund, Department of Psy-chology, Florida Atlantic University.Correspondence concerning this article should be addressed to Bruce J.Ellis, John and Doris Norton School of Family and Consumer Sciences,University of Arizona, McClelland Park, 650 North Park Avenue, Tucson,AZ 85721-0078. E-mail: bjellis@email.arizona.edu Developmental Psychology © 2012 American Psychological Association2012, Vol. 48, No. 3, 591–597 0012-1649/12/$12.00 DOI: 10.1037/a0027651 591  suming and selling drugs, gang membership, early and unprotectedsex, and teen pregnancy. Although such risky behaviors are nothealthy or desirable from a contemporary public policy perspec-tive, they are reliable developmental responses to dangerous orunpredictable rearing environments (Belsky, Schlomer, & Ellis,2012; Dishion, Ha, & Ve´ronneau, 2012; James, Ellis, Schlomer, &Garber, 2012; Gibbons et al., 2012; Simpson, Griskevicius, Kuo,Sung, & Collins, 2012; all this section). This is because, in theworld in which humans evolved, such environments meant ashorter life span and uncertain future. In this context, high-risk adolescent behaviors that increased status among peers and accessto mates increased chances of reproducing and passing on one’sgenes, the ultimate evolutionary metric.The articles in this special section of   Developmental Psychology attempt to demonstrate why an evolutionary analysis is needed tomore fully understand the contexts and contingencies of develop-ment. The three theoretical articles articulate the core evolutionarylogic underlying conditional adaptation (and maladaptation) toboth stressful and supportive environmental conditions over de-velopment. These theoretical articles are then followed by nineempirical articles that test these evolutionary-developmental ideas.Finally, six commentaries evaluate the prospects, pitfalls, andimplications of this body of work. Adaptive (and Maladaptive) Developmental Plasticity One theme running through all of the articles in this specialsection, but especially emphasized in the three theoretical articles,is that natural selection has favored developmental plasticity, withchildren being sensitive to their early environments and adjustingtheir behaviors and cognitions accordingly—usually, but not al-ways, to their advantage. Although the importance of developmentand plasticity in evolutionary explication may seem obvious, itactually runs counter to mainstream thinking during much of the20th century and among some scientists today. For example,following the tenets of the modern synthesis, what happens duringthe course of ontogeny may be of great importance to the individ-ual but inconsequential for natural selection. In essence, the neo-Darwinian mantra became “development doesn’t matter,” or, asmore elegantly expressed by Richard Dawkins (1976, p. 62), “Thedetails of embryological developmental processes, interesting asthey may be, are irrelevant to evolutionary considerations.” Sim-ilarly, evolutionary perspectives on human behavior have oftenbeen viewed (justifiably or not) as supporting a form of geneticdeterminism. For example, Lickliter and Honeycutt (2003), in theircritique of mainstream evolutionary psychology, argued that evo-lutionary psychologists advocate a type of   preformationism , withgenes doing all the heavy explanatory lifting and the environmentmerely facilitating or triggering behavioral outcomes.In contrast, developmentally oriented evolutionary biologistsand psychologists contend that developmental plasticity plays acritical role in evolution and, in fact, is the creative force behindadaptive change (Bjorklund, 2006; Gottlieb, 2002; Ploeger, vander Maas, & Raijmakers, 2008; West-Eberhard, 2003; see alsocommentary by Lickliter, 2012, who states that understandingontogenetic change is necessary to understanding phylogeneticchange). Perhaps more relevant to the present set of articles,evolutionary-developmental psychologists propose that natural se-lection should favor plasticity and sensitivity to local environ-ments. Evolutionary-developmental psychology differs from muchof traditional evolutionary psychology by incorporating the con-cept of   epigenesis,  which explicitly emphasizes the importance andplasticity of Gene    Environment    Development interactions(Blair & Raver, 2012; Lickliter, 2012, this section; see also Bjork-lund, Ellis, & Rosenberg, 2007; Bjorklund & Pellegrini, 2002;Boyce & Ellis, 2005). Such interactions are especially relevant in  Homo sapiens,  whose extended period of immaturity and neuralplasticity permits them to adjust to variations in social environ-ments and anticipate future ones.Such plasticity is not infinite, of course; it is constrained withinboundaries of genetically influenced reaction norms (see Schlicht-ing & Pigliucci, 1998). Moreover, natural selection has shapedchildren’s brains and bodies to be discriminatively sensitive to theenvironment, responding to conditions that have proven “reliableover evolutionary time in predicting the nature of the social andphysical world into which children will mature” (Boyce & Ellis,2005, p. 290). This core logic runs through all three introductorytheoretical articles for the secial section. For example, Blair andRaver (2012) focus on how early experiences can adaptively shapethe development of stress response physiology and related patternsof self-regulation. They provide a test of their ideas in a series of analyses of a large longitudinal data set, examining the interactingeffects of poverty, stress response physiology, and self-regulation.However, modern environments are far different in many waysfrom the environments of our ancestors, increasing the risk of developing phenotypes that are mismatched to one’s current con-text. Frankenhuis and Del Giudice (2012) discuss three ways thatadaptive developmental mechanisms can lead to maladaptive out-comes: (a) natural selection may favor risky strategies that enhancefitness on average but have negative consequences for some indi-viduals (e.g., engaging in aggression to attain high status); (b)individuals may experience a mismatch between previously adap-tive behavior and a changing environment (e.g., as a result of migration or rapid environmental changes); and (c) individualsmay adapt their behavior in response to cues in their early envi-ronment that imperfectly predict later environments. Similarly,Gluckman and Beedle (2012), in their commentary on the Fran-kenhuis and Del Giudice article, note that a mismatch between theindividual and the environment can occur because the environmentchanges for the entire species ( evolutionary novelty ; see also Elliset al., 2012) or because the environment changes for the individualover the course of ontogeny ( developmental mismatch ).Closely related to the problem of mismatch is the phenomenonof developing phenotypes that are adaptive in the evolutionarysense of the term but problematic in modern society. Considerrisky adolescent behavior (Ellis et al., 2012). On the one hand,heightened aggression and delinquency, sexual promiscuity, andgeneral recklessness in adolescence may increase status in domi-nance hierarchies and leverage access to mates; on the other hand,such activities may handicap youths in modern societies (resultingin school dropout, incarceration and lower socioeconomic status;see especially Gibbons et al., 2012). As Ellis and colleagues (2012)argue in the lead article of the special section, the adolescenttransition is an inflection point in the development of social statusand reproductive trajectories; many of the adolescent “problembehaviors” that adults and civil authorities find troublesome mayactually function to increase the sociocompetitive abilities neededto succeed at this critical juncture. As such, interventions need to 592  ELLIS AND BJORKLUND  address the adaptive functions of risky and aggressive behaviorsand work with, not against, powerful adolescent goals and motives.Taken together, the three theoretical articles in the special sec-tion set the stage for the nine empirical articles to follow. First,they demonstrate the importance of applying an evolutionary-developmental perspective to the study of psychopathology (butsee the commentary by Dodge and Albert, 2012, who argue forgreater integration of evolutionary theory with contemporary re-search in developmental psychopathology, rather than viewing oneas a counterposition to the other). Second, the articles describehow conditional adaptive mechanisms regulate plasticity. Andthird, they show how mismatches—between current and ancientenvironments, between anticipated and actual environments, andbetween the goals of the adolescent and those of the greatersociety—can sometimes result in maladaptation. Development of Life History Strategies According to  life history theory  (e.g., Chisholm, 1999), theamount of time and bioenergetic resources that individuals candevote to survival and reproduction is limited; thus, individuals areselected to make trade-offs that prioritize resource expenditures.The most basic trade-off is between somatic effort (resourcesdevoted toward growth and maintenance) and reproductive effort.Resources allocated toward reproduction are further partitionedbetween mating effort (resources devoted to attracting mates andincreasing opportunities for reproduction) and parental/nepotisticeffort (resources devoted to raising already-conceived offspring).These trade-offs are instantiated in key “decisions” over the lifecourse, such as earlier versus later reproduction and quantityversus quality of offspring, that define alternative developmentalpathways, or  life history strategies . These strategies vary on adimension of slow to fast. Organisms pursuing a slower life historystrategy tend to mature more slowly, be more selective in thechoice of mates, have fewer offspring, and invest more effort inparenting. Faster life history strategies, by contrast, involve extraenergetic allocations toward mating effort (including more riskyand aggressive behavior) at a cost to parental effort, leading toearlier pubertal timing and sexual debut, less-stable pair bonding,more children, and less parental investment per child (e.g., Ellis,Figueredo, Brumbach, & Schlomer, 2009).Drawing on life history theory, Belsky, Steinberg, and Draper(1991) published a landmark theory—  psychosocial accelerationtheory —that explicated how developmental contexts regulate vari-ation in life history strategies. The theory broadly linked childhoodexperience, psychological development, somatic development, andreproductive strategy, advancing an integrative model of life his-tory strategy that catalyzed the field of evolutionary-developmental psychology. Psychosocial acceleration theory pos-ited that (a) ecological conditions and family dynamics influencedchildren’s early attachment patterns and behavioral developmentand, through these developmental processes, subsequent pubertaldevelopment and reproductive strategy; and (b) this environmen-tally sensitive developmental system evolved as a means of match-ing life history strategies to environments in a manner that pro-moted survival and reproduction across varying ecologicalcontexts. In their commentary, Nettle, Frankenhuis, and Rickard(2012) argue that psychosocial acceleration theory is biologicallyplausible, insofar as the specified processes meet the conditionsnecessary for adaptive developmental plasticity to evolve.Psychosocial acceleration theory casts a wide net that poten-tially captures a broad range of factors regulating development of life history strategies. That is both the strength and weakness of thetheory. Several articles in the special section propose extensionsand revisions of psychosocial acceleration theory that increase itsspecificity. First, consistent with pervasive notions of cumulativestress, the theory conceptualized ecological context as a singulardimension, ranging from higher stress (e.g., marital discord, singleparenthood, and unstable employment) to lower stress (e.g., spou-sal harmony, adequate financial resources). Since the publicationof psychosocial acceleration theory, however, more recent ad-vances in life history theory (Ellis et al., 2009) have identified, viawithin- and between-species analysis, two distinct ecological di-mensions that account for much of the variation in development of life history strategies, both across and within species: Extrinsicmorbidity–mortality (i.e., external sources of disability and deaththat are relatively insensitive to the adaptive decisions of theorganism) and environmental unpredictability (i.e., variation overtime and space in the fitness costs and benefits afforded byenvironments). Two articles in the special section (Belsky et al.,2012; Simpson et al., 2012) specifically attempt to operationalizeand test for the effects of these two dimensions of ecological stresson development of life history strategies. Employing two majorlongitudinal studies (the National Institute of Child Health andHuman Development Study of Early Child Care and Youth De-velopment and the Minnesota Longitudinal Study of Risk andAdaptation), each article documents that exposures to environmen-tal unpredictability in the first 5 years of life uniquely predictsfaster life history strategies in adolescence and emerging adult-hood.Second, psychosocial acceleration theory is specifically based inlife history theory and does not address the implications of sexualselection theory for understanding variation in life history strate-gies. Sexual selection models, such as Gangestad and Simpson’s(2000) strategic pluralism theory, emphasize social and sexualcompetition as important factors shaping adaptive variation inreproductive strategies. According to this perspective, individualswho are competitively advantaged relative to peers (i.e., whopossess social and physical attributes that make them successful insame-sex competition and targets of choice by the other sex) havemore mating opportunities and, consequently, tend to initiate sex-ual relationships at earlier ages. Incorporating sexual selectionmodels, both Dishion et al. (2012) and James et al. (2012) extendpsychosocial acceleration theory by explicitly integrating peerrelations and intrasexual competitive abilities into the model anddemonstrate that these constructs are crucial to explaining individ-ual differences in development of life history strategies in adoles-cence and emerging adulthood.Sexual selection theory further proposes that men and womenmust solve qualitatively different adaptive problems when negoti-ating life history trade-offs (Trivers, 1972); consequently, thereshould be important sex differences in the tracking of environmen-tal information, or at least in the weight given to specific environ-mental cues. James et al. (2012) employ this perspective to test forsex-specific pathways to early puberty, sexual debut, and sexualrisk taking. Their results document substantive sex differences and 593 AN EVOLUTIONARY ANALYSIS OF DEVELOPMENT  show the value of integrating psychosocial acceleration theorywith sexual selection models.In total, the research of Belsky et al. (2012), Simpson et al.(2012), Dishion et al. (2012), and James et al. (2012) supportsimportant revisions of psychosocial acceleration theory. The first 5years of life appear to be a sensitive period for the acceleratingeffects of environmental unpredictability on development of lifehistory strategies. This replicated empirical phenomenon is impor-tant in moving the field beyond cumulative stress toward anunderstanding of how biobehavioral development adjusts to spe-cific ecological contexts. Further, whatever the effects of ecolog-ical and family contexts on life history strategies, these effects arelikely to operate through, or in concert with, peer relationships andintrasexual competitive abilities. Finally, the srcinal pathwaysspecified by psychosocial acceleration theory need to be recon-ceptualized in terms of sex-specific effects. Differential Susceptibility Although psychosocial acceleration theory has proven useful inguiding research on development of life history strategies, theeffect sizes of ecological and family contexts on behavioral andreproductive outcomes are typically small, leaving much behav-ioral variability unexplained. A possible explanation for thesesmall effects is that children may be differentially susceptible totheir rearing environments. Several related evolutionary modelsposit that natural selection has maintained variation in susceptibil-ity to environmental influence (Belsky, 1997b; Boyce & Ellis,2005; Wolf, van Doorn, & Weissing, 2008). An implication of thisdifferential susceptibility, as articulated by Belsky (1997a), is thatthe small main effects of family context on child outcomes mayoverestimate the impact of rearing environments in some children(low susceptibility, more fixed development) and underestimate itin others (high susceptibility, more plastic development).Differential susceptibility theory recognizes that susceptibilityto the environment is instantiated in multiple genetic polymor-phisms, endophenotypic mechanisms, and behavioral phenotypesthat operate as susceptibility factors, moderating the influence of environmental exposures on developmental and life history out-comes (Ellis et al., 2011). More susceptible individuals, accordingto the theory, are more likely to experience sustained change inresponse to environmental exposures, showing greater susceptibil-ity to environmental contexts that are both positive in character(i.e., afford resources and support that potentially enhance fitness)and negative in character (i.e., embody stressors and adversitiesthat potentially undermine fitness). Gibbons et al. (2012) tested fordifferential susceptibility, on the basis of several genetic markersof neurobiological sensitivity to the environment, in relation tohypotheses drawn from psychosocial acceleration theory. Theirlongitudinal study of African American adolescents investigatedthe effects of several sources of developmental stress (e.g., lowparental investment, racial discrimination) on life history strategiesand associated cognitions. Their results were generally consistentwith psychosocial acceleration theory, both in terms of higherstress contexts promoting faster life history strategies and lowerstress contexts promoting slower life history strategies, but prin-cipally among individuals who possessed more susceptibility al-leles. These findings extend psychosocial acceleration theory bydemonstrating differential susceptibility—showing for whom themodel was most applicable.A core premise of psychosocial acceleration theory is that, evenin early childhood, the developing person’s psychology and be-havior are adapting to local context. The theory proposes thatyoung children growing up under more stressful ecological andfamily conditions tend to develop more insecure attachments, moreopportunistic interpersonal styles, and higher levels of aggression,whereas children growing up in more stable and supportive con-texts tend to develop more secure attachments and reciprocallyrewarding and prosocial interpersonal orientations. Both Sulik etal. (2012) and Eisenberg et al. (2012) tested for these relations ina differential susceptibility research design.Sulik et al. (2012) examined the effects of quality of parentalinvestment on noncompliance and aggression in children from 18to 54 months and whether these effects depended on an establishedgenetic marker of differential susceptibility (Belsky & Pluess,2009): polymorphisms of the serotonin transporter gene. Consis-tent with the differential susceptibility hypothesis, Sulik et al.found that certain genetic haplotypes were associated with greaterresponsivity to both supportive and unsupportive parental behav-ior. Likewise, Eisenberg et al. (2012) tested for the effects of acomposite measure of environmental quality (incorporating socio-economic status and marital adjustment) on development of ag-gression in children from 18 to 54 months and whether theseeffects depended on variation in activity of the parasympatheticnervous system (i.e., respiratory sinus arrhythmia), an establishedmarker of neurobiological susceptibility to context (e.g.,Obradovic´ et al., 2010). Their results provided partial support forthe differential susceptibility hypothesis: Higher baseline parasym-pathetic activation increased susceptibility to more resourced andsupportive family environments, particularly in girls.In total, the srcinal articulation of psychosocial accelerationtheory focused on environmental regulation of life history strate-gies. Although Belsky et al. (1991) acknowledged the importanceof genetic factors and related child effects, such factors were notexplicitly incorporated into the theory. However, as Bugental(2012) notes in her commentary: “Children are both affected byand serve to affect their social environment. This represents aprocess that involves continuous bidirectional changes across thecourse of development” (p. 806). The current work on differentialsusceptibility by Gibbons et al. (2012), Sulik et al. (2012), andEisenberg et al. (2012) constitutes important steps toward identi-fying these transactional processes. Ultimately, psychosocial ac-celeration theory will need to be revised to explicitly incorporatechild characteristics—whether genomic, endophenotypic, or be-havioral—that moderate contextual conditions. As Van IJzendoornand Bakermans-Kranenburg (2012) point out in their commentary,the most productive method for establishing these child character-istics is randomized differential susceptibility experiments, whichare already proving to be feasible and scientifically fruitful. Developmental Programming of Children’sPhysiological Responsivity An outstanding issue in the life history literature is  mechanism :What are the intervening biological pathways through which ex-posures to different familial and ecological conditions regulate theontogeny of slow versus fast life history strategies? One possible 594  ELLIS AND BJORKLUND  answer, investigated in this special section, is variation in activityof the stress response system. Physiological stress responses playa central role in orchestrating the physical and psychosocial de-velopment of both humans and nonhuman species (Ellis, Jackson,& Boyce, 2006; Korte, Koolhaas, Wingfield, & McEwen, 2005).For many organisms, patterns of stress responsivity not only cru-cially contribute to the ability to respond flexibly to challenges andopportunities in the environment but also regulate variation in awide range of adaptive processes and behaviors including (but notlimited to) growth and metabolism, reproductive status and fertil-ity, aggression and risk taking, pair bonding and caregiving, andmemory and learning (reviewed in Del Giudice, Ellis, & Shirtcliff,2011).Given these links, Del Giudice et al. (2011) recently advanced acomprehensive evolutionary-developmental theory of individualdifferences in stress responsivity—the adaptive calibration model(ACM)—that links these individual differences to variations in lifehistory strategy. In the ACM, individual differences in the func-tioning of the stress response system are thought to result largely(though not exclusively) from the operation of evolved mecha-nisms that match the individual’s physiology and behavior to itslocal environmental conditions. Thus, patterns of stress responsiv-ity are seen as adaptive in the biological sense, as they function ina way that ultimately tends to maximize the individual’s survivaland reproduction. According to the theory, activation of the stressresponse system during the first years of life provides crucialinformation about life-history-relevant dimensions of the child’senvironment, namely, danger and unpredictability. This informa-tion is used to adaptively regulate stress responsivity and associ-ated development of life history strategies. Different patterns of baseline activity and responsivity in early development then mod-ulate differential susceptibility to environmental influence andshift susceptible children on alternative pathways, leading to indi-vidual differences in life history strategies.The ACM proposes that, at a very general level, a nonlinearrelation exists between exposures to environmental stress in child-hood and optimal levels of stress responsivity. This nonlinearrelation can be characterized by a taxonomy of four prototypicalresponsivity patterns (labeled  sensitive ,  buffered  ,  vigilant  , and unemotional ). Del Giudice, Hinnant, Ellis, and El-Sheikh (2012)tested key predictions from ACM: that each of the four patterns areassociated with different levels of family stress, that two divergentresponsivity profiles emerge under conditions of low family stress(the high-reactivity sensitive class and low-reactivity bufferedclass), and that two divergent responsivity profiles emerge underconditions of high family stress (the high-reactivity vigilant classand low-reactivity unemotional class). These predictions weregenerally supported in a study of preteenage children. Althoughthe implications of the ACM concern complex social, emotional,and cognitive responses involved in life history strategies, theresponses measured by Del Giudice et al. (2012) were defined interms of specific physiological patterns. Thus, their article consti-tutes only the first steps toward delineating the mechanistic path-ways linking environmental conditions to development of lifehistory strategy.Another approach to addressing this issue is the  Hawk–Dove model of temperament (Korte et al., 2005). Hawk–Dove is a gamewithin the domain of mathematical game theory that models themaintenance of two alternative fighting strategies (Maynard Smith,1982). Hawks represent a strategy characterized by escalation of fighting until either they are injured or the opponent retreats.Doves on the other hand, display to the opponent and then retreatat once if the opponent escalates the fight. Applied to tempera-ment, Hawks and Doves represent distinct ways of responding tostress and challenge that encompass physiological responsivitypatterns, coping styles, emotional states, and behavioral strategies(e.g., bold–shy, aggressive–unaggressive, impulsive–-cautious,and risk prone vs. risk averse; Ellis et al., 2006; Korte et al., 2005).The Hawk–Dove model of temperament generates very detailedhypotheses about the neurogenomic and neuroendocrine mecha-nisms underlying these different temperaments; thus, the model ispotentially well-positioned to guide research on biological path-ways to slow versus fast life history strategies.The major limitation of the Hawk–Dove model, however, is thatit does not link the specified biological pathways to antecedentenvironmental conditions. However, in a very innovative study of 2-year-old children, Sturge-Apple, Davies, Martin, Cicchetti, andHentges (2012) turned this limitation into a strength by using latentprofile analysis to extract Hawk and Dove temperament groupsand then examined the moderating effects of Hawk–Dove profilemembership on children’s physiological and psychological adap-tation to harsh rearing environments. Hawklike strategies werecharacterized by approach, dominant–negative affect, and activity;Dovelike strategies were characterized by avoidance, inhibition,and vulnerable affect. Sturge-Apple et al. (2012) found that basalphysiological activity in Hawks seemingly prepared them forfight–flight responses to adversity; specifically, greater exposureto harsh maternal discipline was linked to elevated sympatheticnervous system activity in Hawks, which predicted increases inexternalizing behavior over time. By contrast, Doves’ basal phys-iological responses seemingly prepared them for vigilance, orient-ing, and inhibitory control; specifically, more exposure to harshmaternal discipline correlated with heightened parasympatheticand cortisol activity and dampened sympathetic nervous systemactivity in Doves, which appeared to amplify the occurrence of depressive and anxious behaviors over time. These complex andfascinating links between rearing environments, temperament, pat-terns of stress responsivity, and behavioral adjustment in earlychildhood may provide critical points of srcin for developmentalpathways leading to slow versus fast life history strategies.In total, variation in activity of the stress response system holdsconsiderable promise for explaining how psychosocial environ-mental factors “get under the skin” to regulate the development of life history strategies. This is a ripe area for future research.Bugental (2012) provides an excellent overview of key issuesinvolved in adaptive calibration of stress responses and theirimplications for conditional adaptation across development. Conclusion Evolutionary thinking has permeated mainstream psychologyover the past two decades. Although such thinking has also beenadopted by many developmental psychologists (e.g., see articles inBurgess & MacDonald, 2005; Ellis & Bjorklund, 2005; Ellis &Boyce, 2011), as a group, developmental psychologists have beenslow to join the evolutionary bandwagon. One reason for thisreluctance is the perception that evolutionary explication implies aform of genetic determinism: If psychological features have 595 AN EVOLUTIONARY ANALYSIS OF DEVELOPMENT
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