Motor Control Theory
Dynamic & Ecological
Approaches
(Large parts adapted from
Wallace, 1993)
Asking the right question/questions

How do we move the way we do?
• Seeks one solution
• A causal influence
•Tends to emphasize neural solutions
•Tends to lead to “hypothetical constructs” to
achieve solutions where neural solutions are not
known
•Tends to shape one’s thinking of control as a
hierarchy
Asking the right question/questions

Why do we move the way we do?
• A different focus
•Tends to make us look at all possible influences on
the shape of movement
•Does not seek one solution, but accepts many
simultaneously
•Tends to shape one’s thinking of control as a
heterarchy
• This is the way we’ll be approaching the problem
A heterarchical theory of control

Or theories...

All have in common the tendency to ask
why rather than how
• Complex systems theory
• Dynamic pattern perspective & synergetics
• Ecological psychology
• The study of relationships among things,
rather than the things themselves

Leads to the study of...
A heterarchical theory of control

Constraints...
• Things which limit our range of movements –
thus “shaping” them

...and affordances
• Things which permit (or even suggest)
certain methods of movement or interaction
with an object
A heterarchical theory of control
From Newell (1986)
Cognition
Motor abilities
Sensory loss
Flexibility
Strength/power
Individual
Capabilities
Cardiovascular
Speed/accuracy
requirements
Surface
type
Lighting
Environmental
Constraints
Visual flow
Environmental stability
moving
Task Demands
seated
standing
Number of tasks
3 categories of constraint (+ examples)
A heterarchical theory of control
From Schmidt &
Fitzpatrick (1993)
Coordination dynamics
Dynamics of
CNS
Dynamics of
action system
Dynamics of
environment
(neural level)
(effector level)
(environmental level)
Connectionism
Action system theory
Laws of perceiving and acting
(ecological psychology)
Processes in coordination dynamics
An example (physical world)

Systems far from equilibrium
Equilibrium
Closed
system
Far from equilibrium
Punch hole
in container
Open system
• There are no instructions determining the pattern of
behavior – just elements of the system interacting
• But this isn’t very complex
Listen to this first…
…then this…
A more complex example

The Benard instability (Prigogine &
Stengers, 1984)
A pan of
about 1cm
depth of oil
random
More
heat
heat
hexagonal
turbulence
• Again, the system self-organizes to these patterns
• Heat is a control parameter (this forces the system to
change its organization)
• (hexagon: from temp gradient + descent of cool
molecules via gravity)
A more complex example

The Benard instability (Prigogine & Stengers,
1984)
A pan of
about 1cm
depth of oil
random
More
heat
heat
hexagonal
turbulent
• Note that each pattern does change, but it resists change
•
also – a property known as stability
Stability and loss of stability are central to dynamic
pattern theory
Pause, consider, then move on…

Getting too big – have to break down
into multiple slide sets