Dynamic Systems Theory

Dynamic Systems Theory

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.

An Example: The Case of the Disappearing

Reflex

An Example: The Case of the Disappearing

Reflex

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