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What is a dynamic system?What is a dynamic system?
A system of elements that A system of elements that changes over timechanges over time
Dynamic Systems: Background 1Dynamic Systems: Background 1 Systems approaches to developmentSystems approaches to development
Developmental psychobiologists working in Developmental psychobiologists working in 1940’s, 1950’s, 1960’s (Schneirla, 1940’s, 1950’s, 1960’s (Schneirla, Lehrman, Kuo)Lehrman, Kuo)
Response to prevalent learning theory and Response to prevalent learning theory and ethological perspectives ethological perspectives
Goal of systems approachGoal of systems approach Eliminate question of what is learned vs. Eliminate question of what is learned vs.
what is innatewhat is innate Behavior is complex, variable, and takes Behavior is complex, variable, and takes
place in continually changing internal and place in continually changing internal and external environmentsexternal environments
Focus on Focus on relationships among componentsrelationships among components as source of changeas source of change
Dynamic Systems: Background 2Dynamic Systems: Background 2 Dynamical systemsDynamical systems
a class of mathematical equations that a class of mathematical equations that describe time-based systems with describe time-based systems with particular properties (e.g., complexity, particular properties (e.g., complexity, nonlinearity)nonlinearity)
examples: chemical reactions, global examples: chemical reactions, global weather changes, dripping faucets, weather changes, dripping faucets, developing humansdeveloping humans
Intellectual Goal of Dynamic Systems Theory
Intellectual Goal of Dynamic Systems Theory
What are the origins of novel What are the origins of novel forms of behavior?forms of behavior?
How can developing systems How can developing systems create something from nothing?create something from nothing?
Traditional ApproachTraditional Approach
Look for sources of new forms in Look for sources of new forms in either the either the organismorganism or the or the
environment environment (or both)(or both)
But….But….
Who turns on the genes?Who turns on the genes? Who decides what the organism Who decides what the organism
absorbs and retains?absorbs and retains? There must be a causal agent who There must be a causal agent who
evaluates information and makes evaluates information and makes decisions.decisions. Novelty doesn’t really develop; it’s there all Novelty doesn’t really develop; it’s there all
along.along.
Dynamic Systems ApproachDynamic Systems Approach
New forms emerge through processes New forms emerge through processes of of self-organizationself-organization patterns and order emerge from the patterns and order emerge from the
interactionsinteractions of the of the multiple componentsmultiple components of a of a complex complex
systemsystem without explicit instructionswithout explicit instructions from organism from organism
or environmentor environment
Extraordinarily complex structural patterns can emerge
from very simple initial conditions in dynamic systems
Extraordinarily complex structural patterns can emerge
from very simple initial conditions in dynamic systems
During development, living things During development, living things with particular properties with particular properties spontaneously organize spontaneously organize themselves into patternsthemselves into patterns
The question isn’t “What causes what to
happen?”
The question isn’t “What causes what to
happen?”
But ratherBut rather
““How does change happen?”How does change happen?”
Not programs, structures, modules, and schemas
Not programs, structures, modules, and schemas
But complexity, stability, and But complexity, stability, and changechange
Little attention has been paid to the process of change in contemporary developmental psychology
Little attention has been paid to the process of change in contemporary developmental psychology
Discovery of Discovery of invariantsinvariants (programs, (programs, stages, structures, modules) that stages, structures, modules) that underlie performance at different agesunderlie performance at different ages
Study of “core abilities”Study of “core abilities”
The “Mind-as-Mountain Stream” MetaphorThe “Mind-as-Mountain Stream” Metaphor Patterns in a fast-moving mountain stream Patterns in a fast-moving mountain stream
are constant and regularare constant and regular Emerge from immediate factors (e.g., rate of Emerge from immediate factors (e.g., rate of
water flow, configuration of stream bed, water flow, configuration of stream bed, weather, characteristics of water molecules)weather, characteristics of water molecules)
And factors operating over different time And factors operating over different time scales (e.g., geological history of mountains, scales (e.g., geological history of mountains, climate, erosion)climate, erosion)
The “Mind-as-Mountain Stream” MetaphorThe “Mind-as-Mountain Stream” Metaphor Behavior is the Behavior is the product of multiple, product of multiple,
contributing influencescontributing influences Each of which has a Each of which has a historyhistory No distinctionNo distinction between real-time between real-time
behavior and lifetime processes that behavior and lifetime processes that contribute to it contribute to it
Behavior is constructed by its own Behavior is constructed by its own history and systemwide activityhistory and systemwide activity
Form is a product of processForm is a product of process
Two Major ConceptsTwo Major Concepts
1.1. Behavior is Behavior is softly assembledsoftly assembled.. Behavior is assembled from all of the Behavior is assembled from all of the
interacting parts interacting parts at the momentat the moment Assembly is flexible, not prescribed by a Assembly is flexible, not prescribed by a
programprogram
Development is a series of patterns evolving and
dissolving over time and, at any point in time, possessing particular degrees of stability.
Development is a series of patterns evolving and
dissolving over time and, at any point in time, possessing particular degrees of stability.
Two Major ConceptsTwo Major Concepts
2.2. Interaction between behavior and Interaction between behavior and subsystems is subsystems is non-linearnon-linear..
A A smallsmall change in one subsystem can change in one subsystem can lead to lead to bigbig changes in behavior. changes in behavior.
NonlinearityNonlinearity Pattern coherence in dynamic systems is Pattern coherence in dynamic systems is
maintained despite internal fluctuations and maintained despite internal fluctuations and small external perturbations (e.g., walking in small external perturbations (e.g., walking in high heels, while chewing gum)high heels, while chewing gum)
But as system parameters or external But as system parameters or external conditions change (e.g., surface slope):conditions change (e.g., surface slope): The old pattern loses coherence and stabilityThe old pattern loses coherence and stability The system finds a qualitatively new patternThe system finds a qualitatively new pattern
This is a nonlinear phase shift
This is a nonlinear phase shift
Gradual changes in a slope Gradual changes in a slope steepness lead to gradual steepness lead to gradual
changes in walking, until a changes in walking, until a small small changechange in slope in slope causes a large causes a large
changechange in gait style. in gait style.
The Disappearing ReflexThe Disappearing Reflex
Newborns take “steps” when held Newborns take “steps” when held upright with feet touching a table.upright with feet touching a table.
Within a few months, the “stepping Within a few months, the “stepping reflex” disappears, and later reappears.reflex” disappears, and later reappears.
How and why does this happen? How and why does this happen?
Account #1: Brain MaturityAccount #1: Brain Maturity
Maturation of voluntary movement Maturation of voluntary movement centers inhibits reflexive stepping.centers inhibits reflexive stepping.
Thelen and Fisher (1982)Thelen and Fisher (1982)
Compared patterns of movement and Compared patterns of movement and muscle activity in babies’ legs as they muscle activity in babies’ legs as they stepped and kicked.stepped and kicked.
Identical patterns of muscle activity Identical patterns of muscle activity during kicking and stepping:during kicking and stepping: contraction to flex legcontraction to flex leg relaxation -- leg pulled back down by relaxation -- leg pulled back down by
gravity and springinessgravity and springiness
The Problem:The Problem:
Kicking and stepping involve the same Kicking and stepping involve the same muscles, and probably the same brain muscles, and probably the same brain areas.areas.
Babies continue to kick even after they Babies continue to kick even after they stop stepping. stop stepping.
Why would stepping disappear and Why would stepping disappear and kicking remain? It doesn’t make sense!kicking remain? It doesn’t make sense!
What else could be going on?What else could be going on?
During the period when stepping is During the period when stepping is suppressed, infants grow very rapidly.suppressed, infants grow very rapidly.
Most growth is in subcutaneous fat, not Most growth is in subcutaneous fat, not muscle.muscle.
Babies’ legs get proportionally heavier, Babies’ legs get proportionally heavier, but not stronger.but not stronger.
More strength is required to lift the legs More strength is required to lift the legs when upright than when supine.when upright than when supine.
Account #2: Dynamic Systems Theory
Account #2: Dynamic Systems Theory
More strength is required to lift the legs when More strength is required to lift the legs when upright than when supine.upright than when supine.
Before babies develop fat legs, they have no Before babies develop fat legs, they have no trouble lifting them in either posture.trouble lifting them in either posture.
As legs get fatter and heavier, muscle As legs get fatter and heavier, muscle strength used to lift the legs isn’t enough to lift strength used to lift the legs isn’t enough to lift them in upright posture. them in upright posture. But kicking when lying down remains.But kicking when lying down remains.
The Fish Tank Experiment (Thelen, Fisher, & Ridley-
Johnson, 1984)
The Fish Tank Experiment (Thelen, Fisher, & Ridley-
Johnson, 1984)
0
5
10
15
20
25
Out-of-Water In-Water
Ave
rage
Ste
ps
per
Min
ute
Weighting the Legs (Thelen, Fisher, & Ridley-
Johnson, 1984)
Weighting the Legs (Thelen, Fisher, & Ridley-
Johnson, 1984)
0
5
10
15
20
25
Without Weights Weights Added
Ave
rage
Ste
ps p
er M
inut
e
Body fat deposition is a growth change that is not
specific to leg movements.
Body fat deposition is a growth change that is not
specific to leg movements.
Yet it results in a Yet it results in a qualitative shiftqualitative shift in behavior.in behavior.
Dynamic Systems Theory: SummaryDynamic Systems Theory: Summary Frames developmental questions in terms of Frames developmental questions in terms of
when systems are stable, when they change, when systems are stable, when they change, and what makes them changeand what makes them change
Views traditionally separate domains as Views traditionally separate domains as subsumed under the same dynamic subsumed under the same dynamic processesprocesses
Captures the richness and complexity of real-Captures the richness and complexity of real-life human behaviorlife human behavior
Dynamic Systems Theory: SummaryDynamic Systems Theory: Summary There is There is no single elementno single element in the child- in the child-
environment system that “determines” environment system that “determines” behavior or “controls” developmental behavior or “controls” developmental changechange Behavior and development are Behavior and development are multiply multiply
determineddetermined Behavior isn’t just in the brain. It’s in the Behavior isn’t just in the brain. It’s in the
brain-body-task-environmentbrain-body-task-environment interaction. interaction.
Dynamic Systems Theory: Summary
Dynamic Systems Theory: Summary
Everything mattersEverything matters