Moving Toward a Grand Theory of Development: In Memory … … · Moving Toward a Grand Theory of...

Moving Toward a Grand Theory of Development: In Memory of Esther Thelen

John P. SpencerUniversity of Iowa

Melissa ClearfieldWhitman College

Daniela CorbettaUniversity of Tennessee

Beverly UlrichUniversity of Michigan

Patricia BuchananBowling Green State University

Gregor SchonerRuhr-Universitat-Bochum

This paper is in memory of Esther Thelen, who passed away while President of the Society for Research in ChildDevelopment. A survey of Esther Thelen’s career reveals a trajectory from early work on simple movements likestepping, to the study of goal-directed reaching, to work on the embodiment of cognition, and, ultimately, to agrand theory of developmentFdynamic systems theory. Four central concepts emerged during her career: (1) anew emphasis on time; (2) the proposal that behavior is softly assembled from the interaction of multiplesubsystems; (3) the embodiment of perception, action, and cognition; and (4) a new respect for individuality.Esther Thelen communicated these ideas to scientists and practitioners alike, so the ultimate benefactors of herwork were children.

Child Development traditionally publishes the Presi-dential Address presented at the biennial meetingsof the Society for Research in Child Development(SRCD). As President, Esther Thelen was slated todeliver the address in 2005, but her death on De-cember 29, 2004, sadly precluded this event. In itsplace, a Memorial Symposium was held. One of Es-ther’s trademark characteristics was to be inclusive,supportive, and collaborativeFto bring people to-gether. This is reflected in the large group of formerpostdocs, doctoral students, and research associateswho collaborated to prepare that symposium, andthen to prepare this archival paper for publication in

Child Development. Esther was not only a mentor tous all, but also a dear friend. Thus, we appreciate theopportunity to share our collective vision of Estherand of her work with you.

Although being a supportive and generous friendwas a core value Esther lived, our goal in this paperis to focus on her science. We use illustrations fromher work to outline the themes emerging from hermovement toward a grand theory of development.We end by proposing several future directions thatare inspired by her work.

The First Steps: Setting the Stage

We begin by examining Esther’s early work in infantand child development. This early phase is perhapsmost vividly described as the kicking, stepping, andwalking period. Many of the themes that character-ize her work were foreshadowed in her earliest pa-pers. These themes were also foreshadowed in thecontext of her early career: Esther followed her ownunique path into the world of developmental theory.

Her earliest graduate research focused on thegrooming behaviors of wasps. Esther was drawn tothis, in part, by the ethologists’ methods of observinganimal behavior in its natural environment and dis-covering the underlying repeated patterns that‘‘marked’’ their function and social impact. Esther

r 2006 by the Society for Research in Child Development, Inc.All rights reserved. 0009-3920/2006/7706-0001

This research was supported by NIH HD 22830 awarded toEsther Thelen. Many people contributed to making the 2005 SRCDPresidential Address such a memorable event. We are deeplygrateful to the coauthors of the four talks: (Part 1) Donna Fisher-Thompson, Jody Jensen, Beatrix Vereijken; (Part 2) Dexter Gorm-ley, J. Cole Galloway; (Part 3) Fred Diedrich, Linda B. Smith; (Part4) Jana Iverson. We would also like to thank Dexter Gormley, ScottRobinson, and Vanessa Simmering for their invaluable technicalassistance, and Brandi Dobbertin, Jeff Johnson, John Lipinski,Larissa Samuelson, and Wendy Troob for their many contributionsboth large and small. Finally, we would like to acknowledge RogerBakeman, who hired Atlanta’s Harmony Chorus for the event. Wewill never forget the moment when Esther finished speaking onvideo and the voices of children echoed through the room singinga South African freedom song. This gave everyone in the room aconcrete example of the power of self-organization.

Correspondence concerning this article should be addressed toJohn P. Spencer, Department of Psychology, 11 Seashore Hall E,University of Iowa, Iowa City, IA 52242. Electronic mail may besent to [email protected].

Child Development, November/December 2006, Volume 77, Number 6, Pages 1521 – 1538

discovered that actions that were repeated impactedsubsequent behaviorFeven if the link between pastand present behaviors was not transparent (Thelen &Farish, 1977). This pushed her to focus on process, onhow and why these behaviors emerged and changed.

Rhythmical Stereotypies

Esther crossed over to the human side of animalstudies with her dissertation. Here, she catalogued thespontaneous behaviors of babies in their naturalsettingsFtheir homesFbiweekly throughout the firstyear of life. Figure 1 illustrates the outcome of herpainstaking efforts. She grouped the actions babiesrepeated into stereotypy categories, such as waving thearms, rocking in place, and kicking their legs. And sheuncovered the developmental trajectory of each ste-reotypy, the timing of peak behaviors, and overlapamong these different behaviors as well as their rela-tion to the emergence of functional motor milestones.For example, kicking movements had their greatestfrequency just before the onset of locomotion androcking on hands and knees appeared just beforecrawling (see Figure 1). Her first publications based onthis work appeared in animal behavior journals (The-len, 1979, 1981a). But in 1981, she published a seminalpaper in Developmental Psychology entitled ‘‘Rhythmicalbehavior in infancy: An ethological perspective.’’

She discovered that these simple, repetitive be-haviors not only provide a window for researchersinterested in studying motor control, but also pro-vide infants with opportunities to become activeparticipants in their own learning. This theme clearlyresonated with researchers studying child develop-

mentFit was quite remarkable that someone trainedin biology drew such a strong and interested re-sponse with her first foray into the developmentalliterature. Perhaps developmental psychologistscould already glean from her cogent arguments theseeds of a grand theory.

Shifting Patterns of Bilateral Coordination: NewbornStepping

Of the many stereotypies infants generate, Estherwas drawn particularly to kicking because it wasrepeated so frequently. Moreover, Esther’s work re-vealed that the coordination patterns that underliekicking were strikingly similar to the patterns thatunderlie newborn stepping. The puzzle was thatnewborn stepping disappeared within the first 3months, whereas kicking continued and increased infrequency. What were the secrets to this mystery?Several researchers had proposed that maturingcortical centers inhibit the primitive stepping reflexor that stepping was phylogenetically programmedto disappear (Andre-Thomas & Autgaerden, 1966;Oppenheim, 1981; Peiper, 1963; Touwen, 1976).

To probe the mystery of the disappearing steps,Esther conducted another longitudinal study, confi-dent that the answer would be revealed by focusingon the detailed development of individual infants andtheir individual differences. Thelen, Fisher, and Rid-ley-Johnson (1984) found a clue in the fact thatchubby babies and those who gained weight fastestwere the first to stop stepping. It appeared that foryoung infants to flex and extend their legs whenupright (stepping; see Figure 2a) demanded more

Rhythmical Behavior

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Figure 1. Frequencies of groups of rhythmical stereotypies during the first year (T 5 torso) (adapted from Thelen, 1981a).

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strength than to flex one’s leg when supine (kicking;see Figure 2b). To test this idea that strength was thekey, Esther and her colleagues conducted two ingen-ious studies. In one, they placed small leg weights on2-month-old babies, similar in amount to the weightthey would gain in the ensuing month. They ob-served a significant drop in newborn stepping. In theother, they submerged older infants, whose steppinghad begun to wane, in water up to chest levels (seeFigure 2c). Step frequency immediately increased;more buoyant legs require less muscle force to lift.

These data demonstrated that traditional explan-ations of neural maturation and innate capacitieswere insufficient to explain the emergence of newpatterns and the flexibility of behavior so evidentin this case. Esther ultimately proposed that step-pingFlike any other behavioral patternFis notsomething one has. Rather, behavior emerges in themoment from the self-organization of multiple compon-ents. This is elegantly illustrated in the steppingstudies which show how the posture of the infant,the strength of an infant’s muscles, and the pull fromthe environment all cohere in a moment in time tocreate or hinder leg movements. And, further, thisexample illustrates how changes in the componentsof this ‘‘system’’ over the longer time scale of de-velopment interact with this real-time, self-organiz-ing view. Quite literally, Esther and her colleagueswere able to create development in the moment by hin-dering the movements of young infants through theapplication of leg weights and recreating stepping inolder infants by cleverly changing the environment.

A Dynamic Theory Emerges as Infants Take a Walk on aTreadmill

The case of the disappearing steps led Esther andher colleagues to move away from single cause

views of development to consider the many, oftennonobvious factors that influence developmentalchange. Critically, however, Esther’s insights offeredmore than generalist statements that developmentwas ‘‘self-organizing’’ and ‘‘everything matters.’’This was brought to the foreground as she beganto probe ties between infants’ behaviors and those ofother complex thermodynamic systems. For in-stance, she noted that both showed evidence ofnonlinearity, both became increasingly less stableduring periods of change, and both displayed atendency to shift toward increased organization(Thelen, 1985; Thelen, Kelso, & Fogel, 1987).

These ideas emerged out of discussions withScott Kelso, who, along with Peter Kugler and Mi-chael Turvey, was beginning to use the principles ofcomplex systems theories developed in physics,mathematics, and chemistry to explain adult humanmotor patterns and coordination (Kelso, Holt,Kugler, & Turvey, 1980; Kelso & Tuller, 1984). Formost of us in the field of development, this ap-proach became known as the dynamic systemsapproach.

Using a clever (some might say bizarre) context,she began to support babies upright on the belt of amotorized treadmill (see Figure 3a) to show thatbehavior self-organizes and that multicausality is atthe core of developmental change. She designed anew longitudinal experiment, studying infants from1 month of age, monthly, for 7 – 10 months. Embed-ded in the design were elements that allowed her toincorporate concepts central to the study of complexsystems: (a) a collective variable captures the inte-grated behavior of the system under study (in thecase of stepping, this was reflected in the phase re-lation between the legs during each step cycle; seeFigure 3b for data on one phase relationFalternat-ing steps); (b) control parametersFsuch as changes in

Figure 2. Panel a shows newborn stepping. Panel b shows kicking. Panel c shows the reemergence of stepping when the infant is placedwaist-deep in water.

Moving Toward a Grand Theory of Development 1523

the strength of leg musclesFdrive the systemthrough periods of change; (c) behavioral change isnonlinearFearly in the first year, infants producedfew steps on the treadmill, but there was a distinctincrease in stepping, typically by 3 months of age,that occurred at different times for different infants(see Figure 3b); (d) behavior is self-organizedFthemotion of the treadmill helped assemble all thecomponents involved in stepping such that infantsshowed stepping patterns when placed on the belteven when they failed to show stepping in othercontexts. The results of this study were published asa monograph for the SRCD (Thelen & Ulrich, 1991).This monograph served as a tutorial that explaineddynamic systems constructs, and it provided a tem-plate for how to apply these constructs to the studyof behavioral development.

A key finding from this monograph is that thesame context elicited different behavior patternsover time and, further, that multiple factors affectedthe patterns that emerged. Early stepping consistedof multiple unstable patterns, including alternating,but also single, parallel, and double steps. As infantsacquired more muscle strength, an improved abilityto control segments of the body, more experience inthe upright posture, and so on, stepping reorgan-ized. Critically, although some form of steppingpattern could be elicited over much of the first yearof postnatal life, walking only emerged after monthsof exploration. Esther and Bev Ulrich concluded thatstepping and, ultimately, walking are not innate orprescribed. Rather, they are self-organized andemergent, reflecting the assembly of multiple sub-systems within the infant’s history of activity incontext (Thelen & Ulrich, 1991).

Guiding Us Through the Next Steps

One of the underlying goals of basic science is tounderstand how systems work sufficiently well tointervene, when necessary, and provide novel solu-tions to help people overcome behavioral problems.Esther’s early experiments utilized tasks that em-phasized kicking, stepping, and walking, behaviorsof particular interest to therapists working with earlymotor disabilities. Researchers working on motorproblems continue to build on her work to studyneuromotor responses of infants born prematurely,as well as infants born with intraventricular hemor-rhages, Down syndrome, cerebral palsy, and spinabifida (Angulo-Barroso, Ulrich, & Tiernan, 2004;Heriza, 1988; Ulrich & Moerchen, 2005; Ulrich,Ulrich, Angulo-Barroso, & Yun, 2001). These trans-lational efforts have proved quite promising, in part,because the contexts Esther created readily elicitmotor activity. By carefully controlling and ma-nipulating the subsystems involved in, for instance,stepping behaviors, one can push the system intonew forms of organization and uncover control pa-rametersFintrinsic or extrinsicFthat give us lever-age to elicit behavioral change. Ultimately, these maybe used to help children assemble new, more stableand more functional behavioral patterns.

Esther published nearly 30 empirical papers inwhich kicking and stepping were the primary focus.But these specific behaviors were merely tools for herfocus on larger theoretical issues of learning anddevelopment. By her painstaking efforts, she in-corporated profound empirical discoveries into herevolving theory. Her goal was to establish a grandtheory of development with general principles that

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Figure 3. Panel a shows an infant walking on a treadmill. Markers on the legs and torso allow the computer to track the motion of the jointswith a high degree of temporal and spatial precision. Panel B shows developmental changes in three infants’ alternating stepping patterns(adapted from Thelen & Ulrich, 1991).

1524 Spencer et al.

apply across varied phenomena and traditionallydisparate domains. And in so doing, she wanted toreach out and reach in, so that the ultimate bene-factors of our work are children. Lofty goals, to besure, but what a wonderful roadmap she left us.

Learning to Reach: Mapping Intentions WithIntrinsic Dynamics

Kicking and stepping are repetitive movements thatare not always performed with an obvious goal inmind. What happens when infants’ movementsbecome clearly goal-oriented? Can the principles ofdynamic systems theory (DST) be applied to thedevelopment of goal-oriented behaviors? Do pat-terns of, for instance, reaching movements self-or-ganize as with kicking and stepping? What doinfants need to learn to obtain a desired toy? Duringthe 1990s, Esther turned to these questions as shesought to generalize her ideas about the nature ofdevelopment.

From a Classical to a Systems View of Infant Reaching

Before Esther’s work, the development of infantreaching was thought to occur in two phases that allinfants traversed in a similar fashion (see Bushnell,1985, for review). In a first developmental phasebeginning at about 3 or 4 months of age, infants’reaches were characterized by very discontinuous,zigzagging trajectories. In a second phase appearingaround 8 months of age, infants began to reach fortoys following a more direct path. The classic ac-count of these two developmental phases focusedalmost entirely on visual control of reaching. Duringthe first phaseFcalled the visually guided reachingphaseFit was assumed that infants’ discontinuoustrajectories reflected their continuous effort tomonitor and visually control the hand trajectory.In the second phaseFcalled the visually elicitedreaching phaseFinfants could look at the target,anticipate an appropriate hand trajectory, and movetheir hand to the target using a fairly straight pathwithout visual monitoring.

Esther’s work on infant reaching challenged thisview of development in two key ways. First, Estherobjected to the heavy emphasis on visual control inearlier accounts. By her view, the development ofreaching did not reflect changes in a single factor;rather, she saw infant reaching as emergent from theassembly of many components. To reach out andgrab an object, infants need to be motivated. Theyneed to be able to localize the object in three-di-

mensional (3-D) space. They need to understandwhether the object is reachable, and they need totransduce the perceived 3-D space into their bodyspace. They need to be able to plan ahead and an-ticipate how the trajectory will unfold. They need tobe able to correct their movements online as theirhand approaches the toy. They need to be able to liftand stabilize the arm as they reach while maintain-ing the stability of the head and the trunk. And, theyneed to remember what works in context and dis-tinguish this from what does not work. Althoughvision is certainly involved in some of these chal-lenges, vision alone cannot account for how infantslearn to reach given these many interacting factors.The challenge, then, is to understand how infantsmanage to assemble all these factors to perform asuccessful reach.

The second point that Esther challenged was theuniversality of the two-phase account of infantreaching. She thought the emphasis needed to be onthe individualFon the unique motor problems eachinfant must overcome due to each infant’s uniquemovement characteristics. In particular, infants needto discover their own, individual, intrinsic move-ment characteristics to develop proper control of thearm and improve movement coordination over time.

Individual Development Matters: A Tale of Two InfantsLearning to Reach

This idea is beautifully illustrated in the story ofHannah and Gabriel learning to reach. Gabriel andHannah were two of the four infants that Esther andher colleagues followed every week over the firstyear of life, from 3 to 52 weeks (e.g., see Thelen et al.,1993; Thelen, Corbetta, & Spencer, 1996). Gabrielbegan reaching when he was 15 weeks old. Hannahperformed her first reach attempts when she was 20weeks old. Each child displayed very different be-havioral characteristics on the weeks before and atreach onset. Gabriel was a very active, energetic in-fant who was flapping both arms up and down alongthe sides of his body. He was often flapping re-gardless of whether the toy was visible or not. Atreach onset, these flapping patterns became an in-tegral part of his goal-oriented movements. Typical-ly, when the toy was approaching his reaching spacefrom the side to the midline, Gabriel flapped andreached for the toy by throwing his arm up andforward. This resulted in swiping at the toy and,occasionally, a toy contact!

Hannah had a completely different style. She wasa much more quiet, lower energy child. At reachonset, her strategy was to stare at the toy intensely


before moving her arm forward and making contactwith the toy. Because she was quiet before reachingand moved her arm forward slowly, her reachesseemed much more controlled and mature thanGabriel’s, but that was only temporary. Indeed, a fewweeks after her first reaches, Hannah became moreactive and she began to show the torturous reachingtrajectories characteristic of Gabriel’s early reaches.

By observing Hannah and Gabriel week by week(along with two other infants), Esther and her col-leagues discovered that the early discontinuities inreaching trajectories did not result from visualguidance of the hand; rather, they emerged as theproduct of high movement speed and associatedlarge passive and active forces combined with a lackof control. This is evident in the kinematic profiles ofGabriel’s and Hannah’s first reaches. Figure 4ashows the displacement of Gabriel’s hand during an8-s segment of motion. This segment shows a con-tinuous movement performed before (solid line),during (dashed line), and after (solid line) the reach.Figure 4b shows the corresponding velocity profilefor this segment of movement, with the onset andoffset of the reaching segment marked by the twovertical bars. Gabriel was initially producing fastmovementsFflapsFwith several high peaks ofvelocity before the toy came into view. Then, whenthe toy appeared, Gabriel turned a flap into areaching movement, again generating a series ofhigh velocity peaks. This reaching movement (da-

shed lines in Figure 4a) was embedded within theongoing stream of activity (solid lines), and the handpath that resulted was very discontinuous.

When we contrast these data with Hannah’s firstreach (see Figure 4c and d), a very different pictureemerges. Hannah’s movement trajectory (see Figure4c) was much simpler and more direct than Gabriel’strajectory. Why is this the case? Hannah’s movementvelocity (see Figure 4d) was almost three times lowerthan Gabriel’s velocity on his first reaching attempt.Thus, while Gabriel was generating high motion-dependent forces that pushed his arm off the in-tended trajectory leading to many corrections, Han-nah generated much smaller forces and was able toproduce a fairly straight trajectory on her first reach.

But Hannah’s seemingly good reaching skill wasonly temporary. During the weeks after these infantsbegan reaching, Gabriel and Hannah modulatedtheir reaches in unique ways to overcome the chal-lenges set up by their individual movement ten-dencies. Specifically, within the few weeks afterreach onset, infants had to learn to either ramp up orclamp down on these movement tendencies to moreeffectively bring their hands to the toy. Gabriel, whowas generating high and fast velocity peaks, had tolearn to slow down his movements. Within 3 weeks,he showed a dramatic decline in the number of vel-ocity peaks in his reaches with an associated increasein path straightness. By contrast, Hannah, who pro-duced much slower movements, had to learn to

Figure 4. Kinematic profiles of Gabriel’s and Hannah’s first reaches during an 8-s segment. (a) Endpoint trajectory of Gabriel’s right armmovement before (solid line), during (dashed line), and after (solid line) reaching for a toy at midline. Gabriel’s reaches were embedded ina continuous movement stream. (b) Corresponding resultant speed profile with demarcation of the reaching segment for Gabriel. (c)Endpoint trajectory of Hannah’s right arm movement when reaching for a toy at midline. (d) Corresponding resultant speed profile withdemarcation of the reaching segment for Hannah (adapted from Thelen et al., 1993).

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inject more energy into her reaches to lift her armagainst gravity and extend her hand up and forwardto the toy. She became more active in the weeksfollowing reach onset, with an increase in movementvelocity and a decrease in path straightness. Thus,Hannah, who looked pretty skilled on her firstreaching attempts, became much worse in the fewweeks following reach onset (Thelen et al., 1993).

Developmental Change Occurs Through Exploration andSelection

In addition to showing that infants follow theirown unique trajectories, this study of infant reachingrevealed that exploration and selection is a key agentof developmental change. To improve over time,each infant experienced and explored a wide rangeof movements, ultimately leading to the discoveryand selection of an optimal way to assemble themany components involved in a reach. Such ex-ploration and selection is evident when we considerthe full set of changes in Gabriel’s and Hannah’sreaching characteristics from reaching onset to theend of their first year of life. Figure 5 shows changesin several kinematic variables across the first year forreaching (Figure 5a – f and i – n) and nonreachingmovements (Figure 5g, h, o, and p) for Gabriel andHannah, respectively (Thelen et al., 1996).

We want to highlight three points about thesedata. First, goal-oriented reaches were always em-bedded within a movement context that showedvery similar kinematic characteristics. For instance,changes in the velocity of infants’ reaches over thefirst year (Figure 5a – c and i – k) paralleled changesin the velocity of infants’ nonreaching movements(Figures 5g, h, o, and p). Thus, when infants weremore active as reflected in periods of higher averagespeeds in nonreaching movements, reaches werealso performed with higher movement speeds (seethe dashed arrow line marking the active period forGabriel and Hannah). Likewise, when infants wereless active as reflected in periods of lower averagespeeds, their reaches were also slower.

Second, these graphs illustrate the concepts ofexploration and selection. Exploration is reflected inan early phase from reach onset to about 30 – 36weeks, where all the speed and trajectory parametersfluctuate up and down and show unstable andchanging curves (see ‘‘exploration phase’’ in Figure5). In this phase, infants explored a wide range ofmovement parameters and movement solutions.They tried fast and slow movements, learning theeffect of these varied speeds on their ability to ac-quire the toy (see Thelen et al., 1996). This explor-

ation generated crucial sensory-motor experienceneeded to learn to calibrate movements and feel theboundaries of control within the reaching task. Thisresulted in selection during a second phase from 30to 36 weeks through the end of the first year (see‘‘selection phase’’ in Figure 5). In this phase, move-ment parameters settled near particular values andshowed much more stability over time as infantsdiscovered, for instance, an optimal reaching speedthat led to more stable and efficient reaches (Thelen& Corbetta, 1994; Thelen et al., 1996).

The third critical point illustrated in Figure 5 isthat Gabriel and Hannah (as well as the other twoinfants in this study) converged on similar move-ment characteristics at the end of the first year des-pite their very different starting points at reach onset.For instance, they converged to a similar number ofmovement units, comparable movement straight-ness, and similar movement speed when contactingthe toy (see the small side arrows in Figure 5). Thisreveals that different developmental pathways canlead to similar outcomes (Thelen et al., 1996).

New Lessons About Learning to Reach

In conclusion, Esther taught us a number ofwonderful lessons about the development of infantreaching. She taught us that developmental changehappens at the level of the individualFall infants donot develop motor skills following the same mold.Instead, each infant experiences unique and differentmovement challenges that call for different solutionsand contribute to the formation of a distinct devel-opmental pathway. In this way, she moved us awayfrom earlier views about the visual guidance of thehand and universal phases of development. Rather,Esther’s work demonstrated that reaches are carvedout from the intrinsic dynamics of infants’ self-gen-erated arm movements as they explore a range ofmovement possibilities and select viable solutions tomeet the demands of the task. In this achievement,body and mind come together as infants assemblethe many components that make a reach: the bio-mechanics of the body, the details of the specificenvironment including the perceived location of thetoy, the speed and force needed to extend the armsaway from the body, the ongoing movement andpostural context, and so on. This integration of bodyand mind is a fundamental characteristic of all goal-directed actions and creates a bridge to an embodiedview of cognition and behavior (for an additionaldiscussion of these lessons, see Corbetta & Thelen,1994, 1996, 1999, 2002; Spencer & Thelen, 2000;Spencer, Vereijken, Diedrich, & Thelen, 2000).


From Action to Embodied Cognition: Bridging theGreat Divide

By this point, Esther had learned that infant motorbehaviorsFboth rhythmic movements with the legsand goal-directed reachesFemerge as the productand confluence of multiple factors. She had dis-covered that learning new movement patterns wasnot the same for all infants; individual infants mustexplore a wide range of behaviors to discover and

select their own unique solutions in the context oftheir intrinsic dynamics and movement history.Finally, progress in motor development requires theintegration of body and mind as infants bring to-gether their physical characteristics with the envir-onmental and movement context to find optimaland flexible behavioral solutions. These were keyinsights in motor development, but did these in-sights extend beyond the realm of stepping, kicking,and reaching?

Figure 5. Kinematic variables of Gabriel’s and Hannah’s reaching and nonreaching movements from the onset of reaching to the end of thefirst year. Panels a – f: means and standard errors of movement speed at reach initiation, average reaching speed, maximum reach speed,straightness of the path, number of movement units, and speed at hand – toy contact for Gabriel. Panels g and h: means and standarderrors of the average speed of all nonreaching movements and the segment of motion before reach initiation for Gabriel. Panels i – n: meansand standard errors of movement speed at reach initiation, average reaching speed, maximum reach speed, straightness of the path,number of movement units, and speed at hand – toy contact for Hannah. Panels o and p: means and standard errors of the average speedof all nonreaching movements and the segment of motion before reach initiation for Hannah. Arrows at the top indicate phases in thedevelopment of reaching skill. Arrows to the right indicate common values of kinematic variables for both infants at the end of the firstyear (adapted from Thelen et al., 1996).

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To address this question, Esther started tothink deeply about the connections between herwork in motor development and work in other do-mains of development. She turned naturally tocognition. Many of the dominant questions in cog-nitive development stem from Piaget, who askedhow children move from the sensorimotor origins ofthought to abstract cognition. Contemporary the-orists have built on this idea, emphasizing thetransformation from perceptual to conceptual pro-cessing (e.g., Mandler, 1988) or the construction ofmore sophisticated forms of cognition built uponinnate ‘‘core’’ knowledge modules (e.g., Spelke,1998). Critically, such approaches have postulated adivide between the ‘‘cognitive’’ and the ‘‘sensori-motor,’’ either through the pursuit of abstract formsof cognition without an understanding of theirsensorimotor origins or by creating a distinctionbetween the cognitive and the sensorimotor fromthe beginning.

This divide was evident when Esther contrastedthe fields of motor development and infant cognition.In motor development, researchers try to understandthe processes that result in a kick or a reach or alookFthese behaviors are interesting in their ownright and reveal characteristics of how perception,action, and cognition all come together to assemble abehavior in context. In infant cognition, by contrast, areach or a look is just a way for infants to demonstrateknowledge, that is a way to get at what infants know.Given this, contemporary theories of infant cognitionhave little to say about the role of the body in mind.

Esther questioned the divide between ‘‘pure’’sensorimotor behavior and cognition. Indeed, incollaboration with Linda Smith, she denied the veryexistence of this divide. She argued that mental ac-tivity is embodiedFthought is always grounded inperception and action (e.g., Thelen, 2000; Thelen &Smith, 1994). This followed Piaget’s tradition in in-voking the importance of the sensorimotor originsof thought. But rather than viewing development asmovement toward the abstract and away from per-ception – action, Esther believed thatFfor infantsand adults alikeFcognition and action are not sep-arate. Instead, cognition is inextricably linked toperception and movement. There is no cognition inthe absence of perception and action.

Embodied Cognition and the Piagetian A-not-B Task

Esther began exploring this connection betweencognition and action through several traditionaldevelopmental tasks. Her detailed analysis of the

dynamics of reaching first led her to a classic Pi-agetian task: the A-not-B task. In this task, infantswatch while a toy is repeatedly hidden in one loca-tion. After a brief delay, infants reach to that locationand uncover the toy. After several trials to this ‘‘A’’location, infants watch while the toy is hidden in asecond ‘‘B’’ location a few inches away. Almostwithout fail, 8- to 10-month-old infants will reachback to the original A location after a short delay,that is, they reach to A and not B (Piaget, 1954; Smith,Thelen, Titzer, & McLin, 1999). According to Piaget(1954), this ‘‘A-not-B error’’ was indicative of infants’incomplete ‘‘object concept.’’ More contemporarytheories have emphasized that problems with spatialcoding, search strategies, or fragile object represen-tations underlie this error (see Marcovitch & Zelazo,1999; Munakata, 1998; Wellman, Cross, & Bartsch,1987).

Instead of thinking about what this task tells usabout what infants know, Esther and her colleaguesbegan their analysis of the A-not-B error by focusingon what infants do. And what they do in this task islook and reach again and again to a poorly specifiedtarget at an A location, only to look and reach againto this location after looking at an event at B. Thus,Esther asked whether the processes that underlierepeatedly looking at and reaching to a locationcould explain the complex pattern of behavior re-vealed by decades of research on this odd error ininfancy.

This question led Esther and her colleagues todevelop the dynamic field theory (DFT) of infantperseverative reaching (Thelen, Schoner, Scheier, &Smith, 2001). This theory captures the processes thatunderlie infants’ decisions to act based on the inte-gration of the immediate environmental stimuli aswell as the short-term and long-term history ofreaching in the same and similar situations. Thetheory is captured schematically in Figure 6. Thetheory starts with the concept of an activation fieldthat captures how infants plan and remember ac-tions. The activation field depicted in Figure 6 showstwo ‘‘peaks’’ of activation distributed across amovement parameter, reaching direction. There isa large peak of activation over the A location and asmaller peak over the B location. This represents astable ‘‘decision’’ to move to A: infants have a strong,supra-threshold representation of A that can sub-serve a reaching movement to this location.

What factors contributed to this activation peak atA? Figure 6 illustrates three inputs that have beenshown to influence infants’ reaching decisions in theA-not-B situation. The first input is the task input.This captures the pattern of activation generated by


the perceptual layout of the task space, for instance,the two covers in Figure 6. It is through this level ofinput that task variations like distinctive targets ormultiple locations have an impact (e.g., Bjork &Cummings, 1984; Bremner, 1978; Butterworth,Jarrett, & Hicks, 1982; Diedrich, Highlands, Thelen,& Smith, 2001). The second inputFthe specificinputFcaptures the pattern of activation producedby the attention-grabbing cue of waving the toy orthe lid (or whatever the experimenter does to drawthe infant’s attention to one location; see Clearfield,Dineva, Smith, Diedrich, & Thelen, 2006; Smith et al.,1999). The final inputFthe preshape inputFcap-tures the pattern of activation produced by the just-previous past. In particular, this input reflects in-fants’ perceptual-motor memory of past reaches tothe A or B locations. In Figure 6, this input has someactivation centered over the A location, reflecting aninfant’s past reaches to A on a series of A trials.

How does the activation fieldFin concert with thethree inputs depicted in Figure 6Fshed light on theprocesses that underlie the A-not-B error? On the firstA trial, infants face two identical reaching targets (theside-by-side covers or lids); thus, the task input issymmetricFit does not specify either location. Asinfants watch, the experimenter cues them to reach tothe A location, by either hiding a toy or waving thelid. This produces a specific input centered at A.When the box is moved within reach after a shortdelay, the specific input to A is strong enough andthe memory for that cue sufficiently long lasting thatthey reach in this direction. This reach also creates a

perceptual-motor memory which lingers after thereach and can ‘‘preshape’’ the activation field onsubsequent trials. Thus, on the second trial to the Alocation, infants are already slightly biased by theirprevious decision to reach in the same direction. Withmore and more reaches to A, the perceptual-motormemory builds up such that, by the first cue to B,there is a relatively strong tendency to reach to A (i.e.,a strong preshape input). This tendency, combinedwith the symmetric task input and a long delay on theB trial, sets infants up to perseverate. In particular,infants perseverate because the specific input at Bfades during the delay and is overtaken by the lin-gering memory of past reaches to A.

Bringing Together Theory and Experiment

Through a combination of simulations and newexperimental evidence, Esther and her colleaguesshowed that the decision to reach to A or B in theA-not-B task could be entirely determined by infants’short-term and long-term history in the task, theiraction planning abilities, and the inputs in the ex-perimental context (e.g., Clearfield, Smith, Diedrich,& Thelen, 2006; Diedrich, Thelen, Smith, & Corbetta,2000; Diedrich et al., 2001). For instance, by thinkingabout the dynamics of reaching and looking, theseresearchers demonstrated that hidden toys were un-necessary to produce the error (Smith et al., 1999).Similarly, visual distractions had a profound influ-ence on infants’ pattern of reachingFa simple tapon the table near A or B could create stronger

movem

ent

parameter

A location

B location

activation field

specificinput

taskinput

preshapeinput

Figure 6. Schematic of the A-not-B task. The infant (far left) sits in front of two targets (A and B locations). The activation field (in light gray)captures the infant’s decision to reach as a pattern of activation distributed across the behavioral dimension (the direction of the reach). Whenactivation reaches threshold at one of the locations, the infant decides to reach to that location. Three inputs contribute to the activation level(see labels at bottom right). The task input represents the perceptual layout of the space, including the two reaching targets. The specific inputis the transient event that draws attention to one location (i.e., the experimenter hides the toy at A). The preshape input represents the infant’sperceptual-motor memory of previous reaches to A. In this example, the task input is equal for both the A and B locations, but there is a peakat A from the specific input (the experimenter cued the A location) and from the preshape (the infant had previously reached to A). Thisresults in a suprathreshold peak at A (see light gray activation field), which results in a reach to A.

1530 Spencer et al.

perseveration or create a tendency to reach correctlyto B (Smith et al., 1999). They also showed that theprobability of perseverating on the B trials is afunction of the number of reaches to A on the Atrials: the more reaches to A, the stronger the ‘‘pull’’to A on the B trials; the more spontaneous reaches toB on the A trials, the weaker the pull to A on the Btrials (Diedrich et al., 2001; Smith et al., 1999; see alsoMarcovitch & Zelazo, 1999).

In several additional studies, Esther and her col-leagues demonstrated that infants’ decision to reachto A or B was truly embodiedFthere was an ob-ligatory coupling between body and mind. For in-stance, perseveration is tightly linked to infants’developing reaching abilities (Clearfield & Thelen,2001; Clearfield, Smith, et al., 2006; Diedrich et al.,2001). Initially, when infants are very unskilled, theyreach correctly in the A-not-B task. According to theDFT, this occurs because infants’ perceptual-motortraces get ‘‘smeared out’’ as they reach for the A lo-cation in different ways from trial to trial (Clearfield,Smith, et al., 2006). Thus, there is less of a bias to Aon the B trial due to a less focused preshape input(see Figure 6). As another example, Esther and hercolleagues showed that changes in the feel of thebody between the A and B trials can disrupt per-severation (Clearfield, Diedrich, Smith, & Thelen,2006). When infants’ arms were weighted during theA trials and the weights were removed in betweenthe A and B trials, infants reached correctly to B onthe subsequent B trials! Infants also reached correctlyon the B trials when weights were added in betweenthe A and B trials. By contrast, when infants woreweights through an entire session, they perseveratedat the usual rate. Thus, disrupting the feel of thearms between the A and B trials was enough todisrupt perseveration; as long as the arms felt thesame throughout, infants perseverated at the normalrate.

In her Presidential Address to the InternationalSociety on Infant Studies in 1998, Esther outlined theimportance of these findings: what infants know isalways assembled, in the moment, with contribu-tions from memory, attention, and action (Thelen,2000). Cognition is embodied. Infants’ decision toreach is based on much more than whether or notthey have an object concept. Instead, the decision toreach is based on what the infants have just done,their reaching skill, the feel of the body, the salienceof the cue, and the perceptual layout of the task.Thus, this reaching task that was assumed to providea direct window into infants’ abstract concepts isactually a window into the complex interactionsamong perception, action, and cognition in infancy.

Embodied Cognition and the Dynamics of InfantHabituation

Armed with this new understanding of embodi-ment in infancy, Esther moved on to examine an-other task thought to provide a window into infants’mindsFinfant habituation. Infant habituation taskscomprise the backbone of the field of infant cogni-tion. Infants are shown a display or an event overand over until looking time decreases. Then, they areshown a slightly different ‘‘test’’ display or event.If looking time increases, researchers state with cer-tainty that infants discriminated between the twoevents and, perhaps, that this reflects infants’knowledge or understanding of some concept. Aswith the A-not-B paradigm, this leap from what in-fants do to what infants know troubled Esther. Shebegan to think about what infants do in this task:they attend to the display, they visually process it,and they look and look away from the display. Herfocus was on the multiple causes that produce thesebehaviors, and how the history of the system mightinfluence whether or not infants look at the displayat test.

To understand the complex looking dynamics atwork in infant habituation, Esther and GregorSchoner applied the concepts of the DFT to a classichabituation task (Schoner & Thelen, 2006). In par-ticular, they focused on how the trial-to-trial historyof perceiving, attending, and acting in context in-fluences the ‘‘decisions’’ infants make to look or notlook at stimuli in habituation tasks. Using a series ofsimulations, they showed how multiple factors in-fluence infants’ decisions to look at a stimulus: thehistory of looks across trials, the salience of the dis-plays, the number and order of habituation andtest trials, and the complexity of the displays.They concluded thatFas with the A-not-B para-digmFhabituation tasks are not a window into in-fants’ minds, divorced from attention, perception,and action. Rather, infants’ decisions to look or notto look are a result of the complex interactionsamong these diverse and fully embodied processes.

From Knowing to Acting in the World

The importance of Esther’s work on infant cog-nition is not just in the particular tasks or findingsthat she and her colleagues eloquently explained.Rather, what we take away from this work is thatcognition is embodiedFand this has concrete con-ceptual and methodological consequences. This viewof cognition shifts the focus away from what babiesknow in the abstract to a shared emphasis on the


perceptual and movement dynamics that producebehavior. The traditional view that reaching orlooking gives us direct access to the contents of mindis no longer tenable. As long as our entry into infantcognition is through reaching or looking, the dy-namics of these behaviors must be considered, thatis, the developmental history and real-time dynam-ics of the response cannot be separated from theconstructs the response is designed to measure.Perception and action are not bystanders in cogni-tion. Rather, cognition always reflects the dynamicinterplay of mental and bodily processes embeddedwithin a rich context.

Reaching Out: Dynamic Systems in the World

Movement played a central role in Esther’s career,not simply in the topics she studied, but movementin her own thinking as well. Two trajectories emergefrom a survey of her career. The first is movementfrom studying simple responses to increasinglycomplex phenomena, including cognition. In Es-ther’s early career, she discovered how infantsassemble simple movements like stepping andwalking on a treadmill from multiple componentsincluding the spring-like character of leg muscles.Later, when studying goal-directed actions likereaching, she discovered that the characteristics ofinfants’ bodies as well as their energy levels had aprofound influence on the emergence of goal-di-rected actions and in generating the torturous pathsso typical of early reaching. But through a process ofexploration and selection, infants harnessed theseintrinsic dynamics as body and mind came togetherto make straighter, more efficient reaches. Theseearly hints at the embodiment of cognition werebrought to the foreground as Esther moved into thedomain of infant cognition. Here, she and her col-leagues specified the neural dynamics at work asinfants made decisions about where to reach in theA-not-B task or where to look in a habituation task.

Importantly, as Esther moved from simple re-sponses to increasingly complex phenomena, she didnot partition the child up as the focus expanded.Rather, she viewed the child-in-context as a complexsystem of reciprocally coupled and reciprocallyinteractive components. Moreover, she showed animpressive ability to integrate seemingly disparatephenomena: from leg muscles and rhythmic move-ments to arm muscles and goal-directed actions;from reaching movements and movement speed tothe A-not-B task and the role of motor skill in thisclassic cognitive task; from reaching and looking at

lids and toys to looking at complex stimuli in infanthabituation.

These commonalties led Esther to emphasize therole of general processes in shaping development. Thisview ran counter to other modern proposals aboutthe state of developmental theory, which claim that‘‘Piaget was wrong: broad, general explanationsseem ‘increasingly implausible’ (Gopnik, 1996, p.221) and efforts are better spent working out thedetails, domain-by-domain. The traditional big is-sues of developmental theory . . . should be cast asidein favor of specific theories about content’’ (Thelen &Bates, 2003, p. 378). In contrast to this view, Estherand Elizabeth Bates wrote, ‘‘we state forthrightly thatwe do believe that there are general principles ofdevelopment: mechanisms and processes that holdtrue whatever the content domain’’ (Thelen & Bates,2003, p. 378).

Esther’s pursuit of these general developmentalprocesses highlights the second trajectory in hercareerFmovement from metaphor to formal theory.Her career began with an ethological and ecologicalperspective that included intensive observations ofchildren in a number of detailed longitudinal studiesof kicking and reaching (e.g., Thelen, 1981b; Thelenet al., 1993). This large body of empirical work ledinitially to a systems view and a rejection of nativismas a viable approach to understanding development.Later, in a seminal paper coauthored with BeverlyUlrich, Esther introduced concepts of DST to devel-opmental researchersFcollective variables, controlparameters, nonlinearity, self-organization, attrac-tors, stability, and multicausalityFlaying out a re-cipe on how to study developmental process (Thelen& Ulrich, 1991). These ideas were expanded in her1994 book with Linda Smith (Thelen & Smith, 1994).This book postulated that systems thinking was notsolely applicable to motor development and motorcontrol; rather, the concepts of DST could be appliedacross all domains of development including cogni-tion (for elegant demonstrations of this, see Fischer &Bidell, 1998; Lewis, 2000; van der Maas et al., inpress; Van Geert, 1998). Esther, Linda Smith, andtheir colleagues demonstrated this forcefully in aseries of elegant and counterintuitive experiments onthe Piagetian A-not-B error (Smith et al., 1999).

Next, Esther sought to formalize the concepts ofDST, creating a dialogue between formal theory andempirical work. Her initial discussions with ScottKelso led her to a relative phase model of rhythmicmovements, but it was her collaboration with GregorSchoner and their work on the DFT that solidifiedthe theory – experiment link. This link produced twoformal models of classic findings in infant cognition

1532 Spencer et al.

(Schoner & Thelen, 2006; Thelen et al., 2001) and hasled to a host of innovations in other domains (e.g.,Bastian, Schoner, & Riehle, 2003; Erlhagen & Schoner,2002; Schutte, Spencer, & Schoner, 2003; Spencer &Schoner, 2003; Spencer, Simmering, & Schutte, 2006).

Although Esther had immense enthusiasm forformal theoretical work, she always emphasized thereciprocal interaction among different scientific ap-proaches to the study of development. She refused toinvest too heavily in a particular mathematicalmodel, preferring to emphasize the importance ofconceptual thinking, telling a good story, and havinga good metaphor: ‘‘the role of formal models is tomake . . . underlying assumptions extremely precise.The specific form of the model is, thus, less import-ant than the general principles of development onwhich it is based’’ (Thelen & Bates, 2003, p. 378).

This emphasis came through in the clarity of herwriting and the clarity of her thought. As an ex-ample, in a wonderful article targeted towardundergraduates entitled ‘‘The Improvising Infant:Learning about Learning to Move,’’ Esther compareddevelopment to improvisational jazz (Thelen, 1998).She discussed how infants create new solutions stepby step over development as they carve out theirown unique pathway. Thus, development is morelike improvisational jazz, with the infant as a musi-cian and less like a mechanistic process driven bygenes. And, as with jazz, the music infants create asthey learn to move and explore must be consideredas a whole pattern rather than a sequence of indi-vidual notes. Note that Esther actually brought avariant of this metaphor into reality by collaboratingwith Helga Winold to study the dynamics of ex-pertise in cello performance (Winold, Thelen, &Ulrich, 1994).

A New Grand Theory of Development

Given Esther’s emphasis on general develop-mental processes, we can ask where the two trajec-tories of her career led. The answer is that they led toa new grand theory of development, DST. Fourcentral concepts of the theory emerged across Es-ther’s career and have been evident in the examplesmentioned previously. First, DST creates a new em-phasis on timeFbehavior emerges in the moment, butthe effects of each behavioral decision accumulateover longer time scales, as each change sets the stagefor future changes. This theme is evident in Esther’smany detailed longitudinal studies showing a cas-cade of influences over different time scales (e.g.,Thelen & Ulrich, 1991; Thelen et al., 1993). Second,

according to DST, behavior is multiply determined andsoftly assembled from the nonlinear interactions ofmultiple subsystems. The concept of soft assembly isbeautifully illustrated in some of Esther’s earliestwork. For example, in her work on the disappearingsteps, Esther showed how stepping patterns comeand go depending on the weight of the infant’s legs,whether the infant is in water or not, whether theinfant is upright, lying down, and so on (e.g., Thelenet al., 1984). Note that this concept of soft assembly iscritical to allow the child to act in a changing andvariable world. Moreover, soft assembly provides anatural foundation for exploration and selection be-cause behavioral patterns are not fixed, but varyingand flexible.

The third central concept of DST is embodi-mentFperception, action, and cognition form an in-tegrated system that cannot be partitioned. Esther andLinda Smith emphasized this latter point in their 1994book: ‘‘We, like the symbolic computational theorist,view cognition as all one kind; but in our view, it is allembodied, all distributed, all activity, all a complexevent in time’’ (Thelen & Smith, 1994, p. 337). Theembodiment of behavior is, perhaps, best illustrated inthe weighted limbs studies using the A-not-B task: bysimply changing the feel of the arms between the Aand B trials, Esther and her colleagues could createperseverative or accurate responding in the task(Diedrich, Clearfield, Smith, & Thelen, 2005). Fourth,DST shows a new respect for individuality. Develop-ment happens in individual children solving individ-ual problems in their own unique ways. This theme isbeautifully illustrated in the story of Gabriel andHannah learning to reach (e.g., Thelen et al., 1996).

Putting these themes together, we can sketch theview of development that Esther championed (seeFigure 7). We start with a child-in-context composedof multiple components at different levels of an in-tegrated system. These components include neuraldynamics captured by the DFT (Bastian, Riehle,Erlhagen, & Schoner, 1998; Erlhagen, Bastian, Jancke,Riehle, & Schoner, 1999; Jancke et al., 1999; Thelen etal., 2001), neural oscillations critical to motor controland rhythmic actions (Kelso, 1995), the spring-likecharacteristics of muscles (e.g., Thelen & Ulrich,1991), and so on. Critically, these components arefully embodied and reciprocally coupled (see thebidirectional arrows in Figure 7). Moreover, they arecoupled together in a softly assembled way that isgrounded in the sensorimotor world.

What happens, then, as the child interacts with theworld from second to second, minute to minute,situation to situation? Over short time scales, learn-ing occurs. What is learning from a dynamic systems


view? At a general level, the infant is carving outindividual solutions to the real-world problem she isfacing, in this case, grabbing an attractive ball (seeFigure 7). In dynamic systems concepts, she isforming stable attractors or patterns. Such stabilitycan emerge at one levelFfor instance, at the level ofneural dynamics captured by the DFTFor stabilitycan be reflected in changes in the coupling of com-ponents (see the solid arrows in Figure 7). Import-antly, though, stability is not an end-stateFthere isalways a delicate balance between stability and in-stability. This allows for improvisation on a theme;for the infant to use stable solutions, and to alsodiscover novel solutions that arise through explor-ation and often through accident.

Moving forward, these real-time and learning-time processes are integrated over longer time scalesto form a unique developmental trajectory. Here, theinfant continues to carve out stable solutions, andshe learns to flexibly shift from one solution to an-other as the situation or her motivations change.Thus, she can flexibly shift from one stable patternwhen reaching for the ball, to another stable patternwhen confronted with two identical hiding locationsin an A-not-B situation, to another stable pattern asshe has to reach for the blanket to retrieve the ball

(see Figure 7). Note that these solutions are particu-lar to this child and this developmental trajectory isunique to this child. Nevertheless, the processes thatwork over these time scales are general.

Esther and Linda Smith conveyed their excite-ment about this view of development in their 1994book: ‘‘What can a dynamic approach do? A dy-namic approach can change the way you think aboutdevelopment and it can change the way you conductresearch in development. Once we began to viewdevelopment from a dynamic and selectionist ap-proach, we found the ideas so powerful that wecould never go back to other ways of thinking. Everypaper we read, every talk we heard, every new bit ofdata from our labs took on new meaning . . . The finaltest of dynamics in development, of course, is in itsusefulness to a wide range of scholars. We hopereaders will accept the challenge of the new way ofthinking and working and we look forward to thereport card’’ (Thelen & Smith, 1994, pp. 341 – 342).

Looking to the Future: Challenges for a Dynamic SystemsApproach

As with all grand theories, there are many chal-lenges that lie ahead. We highlight two that were

learning

Changing stability within and across levels of system

development

Flexibly shifting among stable solutions as

situation chanes

……

Figure 7. A depiction of learning and development from a dynamic systems perspective. Each image of the infant captures one time pointin learning/development with time moving from left to right. The infant is viewed as an integrated system consisting of multiple, re-ciprocally coupled components (see the bidirectional arrows) embedded within a specific context. The components depicted includeneural dynamics (captured by the simulation of the DFT in the infant’s head), oscillatory dynamics (see oscillation in the brain and spinalcord), and the springy character of muscles (see springs in the arm and leg). Learning is about changing stability within and across levels.This is illustrated by the solid line highlighting simulation in the infant’s head, and the shift from dotted arrows in the first learning step tosolid arrows in the second. Development is about flexibly shifting among stable solutions, that is, being able to flexibly shift from thedynamic organization needed to reach for the ball, to the dynamic organization needed to reach for the box, to the dynamic organizationneeded to grab the blanket to slide the ball forward (see dashed highlighting and dashed arrows in the final time step).

1534 Spencer et al.

emerging as critical next steps in Esther’s work. Thefirst challenge is to create dynamical systems thatchange themselves and, in this way, begin to integratethe multiple time scales of development. Here, Es-ther thought dynamical systems theorists mightborrow insights from connectionist approaches tolearning (for related ideas, see Spencer & Thelen,2003; Spencer, Thomas, & McClelland, in press).Nevertheless, Esther thought that learning extendedbeyond what could be captured by accumulating thestatistics of experience. Rather, she thought a newview of learning might emerge by integratinginsights from connectionism with the rich under-standing of real-time dynamics she and her col-leagues explored (e.g., Schoner & Thelen, 2006;Thelen et al., 2001). Esther also thought that devel-opmental scientists might gain insights about inte-grating time scales by looking into the field ofdevelopmental robotics to discover the contingenciesthat may structure the learning experience of theperceiving and acting infant.

A second challenge facing DST is to develop dy-namic systems that create themselves through pro-cesses of exploration and selection. The theme ofexploration and selection was present in Esther’swork quite early and played a central role in her 1994book with Linda Smith. There, they incorporatedGerald Edelman’s ideas about ‘‘Neural Darwinism’’(see Edelman, 1987) to understand how nervoussystems can create new insights about the world viathe redundant, degenerate neural signals thatunderlie experience. To date, however, it is not clearhow to integrate this view with, for instance, therichly structured behavioral dimensions and neuraldynamics that underlie the DFT (Thelen et al., 2001).Moreover, a critical challenge with selectionist ideasis to understand generalizationFhow the novel as-sociations and insights created in-the-moment areintegrated together to extend across situations. Es-ther thought that action might provide a commonlink across diverse experiences, given the embodi-ment of cognition and the fact that the body is al-ways present, shaping and structuring experience.

Looking to the Future: Reaching Out

Another kind of challenge is to reach out andbring DST into the world. There are two senses inwhich this needs to be done. First, Esther thoughtthat DST needed a richer sense of action in the realworld to capture the emotional and motivationalside of development. Thus, there must be more thantoys and treadmills in the child’s world (see Figure7); we must add mothers and fathers and consider

the influences of whole families and large social andcultural groups (for steps in this direction, see Fogel,Nwokah, Dedo, & Messinger, 1992; Lewis, 2000).Second, Esther sought a stronger emphasis on dialogwith parents, practitioners, and policymakers totranslate theory into practice with infants, children,and adults needing assistance. Thus, Esther soughtto take her knowledge of empirical findings, con-ceptual theory, and formal theory and bring it to thelevel of individual children in the world.

We have already mentioned two of Esther’stranslational projects: working with physical andoccupational therapists to improve the lives of, forinstance, children with Down syndrome (Ulrichet al., 2001) and working with musical scholars tostudy the development of expertise in the training ofcellists (Winold et al., 1994). A third translationaleffort played a central role in the final phase of Es-ther’s career: she became a Guild Certified FeldenkraisPractitionerCM. Here, she asked whether the prin-ciples of DST that shed light on motor developmentcould foster a deeper understanding of the Fel-denkrais Method

s

of somatic education. Importantly,she did not view this translational project as a one-way flow of information from researchers to theapplied world. Rather, she had a vision of reciprocaldialogFthat practitioners could gain theoreticalgrounding, but basic researchers could gain insightsinto the generality of ideas as well as novel insightsinto developmental process.

Why was Esther drawn to the Feldenkrais Method?The Feldenkrais Method uses subtle variation, innov-ation, and explicit differentiation of the perception ofmovements to free people from habitual patternsand allow new movement solutions to emerge. Thus,Feldenkrais practitioners introduce novel and/or dif-ficult movement problems to help bring movementperception into awareness. This also serves to fosternew modes of coordination and to destabilize oldhabits, allowing the discovery of new ways to move.To Esther and to many others, this view of move-ment education has a natural affinity with conceptsof DST (Buchanan & Ulrich, 2001). Thus, toward theend of her career, Esther began to conduct researchstudies on the effects of the Feldenkrais Method onhealthy adults; she participated in and organizedsymposia to promote dialog among researchers andFeldenkrais practitioners; and she looked forward to asecond career giving Feldenkrais lessons to infantsand children. Sadly, this second career was notrealized, but Esther’s efforts to reach out and bringdynamic systems concepts into the world continue.

We end with Esther’s own wordsFwith a tran-script from a conversation between Roger Russell


(a Certified Feldenkrais Trainer) and Esther that tookplace in Amsterdam in 1998. In this interview, Estherexpresses the pleasure she received from translatingdynamic systems ideas to others and her vision ofthe future. Central to this vision was the hope thather theoretical ideas would be useful, not just to re-searchers in the field of child development, but topeople in general. That is, she hoped these ideaswould have a profound effect on the way peoplethink about development, as well as how they thinkof themselvesFas embodied, grounded, ever-chan-ging, ever improvising people in the world.

Roger Russell: ‘‘You’ve been involved in the aca-demic field where most of the people who listen toyou are other academics asking academic ques-tions.’’Esther Thelen: ‘‘I’ve actually talked to a lot ofpractitioners of various kinds.’’Roger Russell: ‘‘What interests them [the practi-tioners] in what you’re saying?’’Esther Thelen: ‘‘I think that people dealing withadults and children who have some sort of prob-lem . . . children with speech problems, with mo-tor problems, adults with problems, emotionaland so on, are now really very interested in theparallels . . . between the processes of change asthey occur in development and the processes ofchange as they may happen in some sort of edu-cational or therapeutic encounter. And a lot ofpeople have told me that they’re looking for sometheoretical basis for what they do. I’ve had thishappen over and over where people will come upto me and say, ‘well, this is very interesting andyou are describing perfectly what I do in myspeech therapy!’ or ‘what I do in my psychother-apyFthis is how I approach therapy! But I havenot had a theoretical kind of rationale for it before[that is] so explicit about how people change.’So, to have it spelled out as a developmentalprocessFI think it’s very honest to put change,dysfunctional outcomes and functional outcomesall in the same vocabulary. In other words, peopleare . . . looking for models that are not just medicalmodels of how things go badly and how youchange them. And the implications of the kinds ofways that we’re thinking are that you may havedysfunctional outcomes out of the same pro-cessesFdevelopmental processesFthat led tomore adaptive outcomes . . . Therefore, you canlook toward developmental processes to thinkabout how to move people beyond their . . . mal-adaptive ways of interacting either in relation-ships or in their skills or so on. So I think that’s

been quite attractive and I’m pleased, if, in fact,this will happen that these things will come to-gether.’’Roger Russell: ‘‘What pleases you about it?’’Esther Thelen: ‘‘Well, it’s nice to know thatsomething that you’ve done and that your col-leagues and your students have done actuallymay be useful to someone, other than just, youknow, giving your papers to other academics!And especially . . . if it will inspire therapists tothink differently and maybe try new things. Ithink that would be a lovely way of translatingbasic laboratory and theoretical work. I started inthis field because I’m interested in how thingswork. I want to know, ‘gee, why does it changelike this? What happens?’ without much thoughtof, well, is this useful to anyone. Basic, just basicscientific curiosity. But, if at the same time it turnsout that it can be useful at least a little bit, thenthat’s wonderful!’’

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