Behavioral Theories of Motor
Control
Chapter 3
Overview

Now that we’ve looked at response
preparation, what happens during the response
programming stage?
Early Motor Program Theories

Proposed that for each movement to be made,
a separate motor program existed and was
stored in memory

Two problems:
–
Storage: Hard drive (brain) could run out of space
–
Novel responses: How do you respond to an action
never done before?
Command Center

Decision> appropriate plan retrieved from
memory> instructions to rest of body for action
Open Loop Systems

Open loop
–
Action plans generated by command center then
carried out by the limbs and muscles without
modification
Command Center
Action
Mechanical Example:Sending Email
Closed Loop Systems

Closed loop
–
Command center generates action plan that initiates
the movement
–
Feedback is used to modify on-going action
Action
Command
Center
Feedback
Mechanical Example: Thermostat
Slow Vs. Rapid Movements

Motor control uses both open and closed loop
systems
–
Movements are planned in advance, initiated &
executed with little modification (remember the fake in
PRP?)
–
If a rapid movement, feedback will be used for the
next attempt
–
For slower movements, open loop begins the
movement and closed loop will continue to completion
Problem:

How does a person do a novel motor skill?

Motor Program
–
Abstract representation of a movement plan
–
Stored in memory
–
Issues instructions that are carried out by the limbs
and muscles
Generalized Motor Program (GMP)

Represents a class of actions or pattern of
movement that can be modified to yield various
response outcomes

Invariant features
–

Relatively fixed underlying features that define a GMP
Parameters
–
Flexible features that define how to execute a GMP
Fixed vs. Flexible Features

Write your name with the following:
–
–
–
–
–
–

Your dominant hand
Your non-dominant hand
Pen in your mouth
Pressing very hard
Pressing very soft
Write quickly, then slowly
Which aspects were fixed? Flexible?
Invariant Features

Relatively fixed underlying features
–
Sequence of actions or components
–
Relative timing

–
Internal rhythm of the skill : the amount of time to write
each letter of your name will stay the same whether writing
fast or slow
Relative force

Internal force relationship: The amount of force given to
write each letter stays proportionally the same whether
pressing hard or soft
Parameters

Adaptable features of program

Easily modified from one performance to
another to produce variations of a motor
response
–
Overall duration: Fast or slow
–
Overall force: Hard or soft
–
Muscle selection: Writing with hand or foot?
Review Question

When swimmers use hand paddles or when
baseball hitters swing heavier bats, does this
manipulate invariant features or parameter
features?
–
–
When might such an action hinder the development
of correct technique?
What signs would you look for to avoid this
problem?
Schema

Rule or relationship that directs decision-making
when a learner is faced with a movement problem

Developed by abstracting 4 sources of information for
each performance attempt
1.
Initial conditions present at start of movement
2.
Response specifications: parameters used in the
execution of the movement
3.
Sensory consequences: what did the action feel like?
4.
Response outcome: how successful was the response?
Schema Development


For each movement attempt the four sources
of information are stored in memory briefly
Feedback from the attempt verifies
–
–

How successful was the performance?
Do I need to change the movement?
With each additional attempt, the strength of
the schema increases when you compare one
attempt to the next
Motor Response Schema

Recall schema
–
Responsible for organizing the motor program


What do I need to do?>What conditions exist?>What
parameters & invariant features are required?>Execute the
response
Recognition schema
–
Responsible for the evaluation of a movement
attempt : Was the movement correct?

Error signal updates the recall schema
Dynamic System Theory

Movement pattern is thought to emerge or selforganize as a function of the ever-changing
constraints placed upon it
Constraints


Defined as the boundaries that limit the
movement capabilities of an individual
Three types
–
Organismic: structural or functional


–
–
Body type, wt, ht
Psychological, cognitive, emotional
Environmental:wind, light, flat surface, grassy
Task
Task Constraints


The goal of task: a certain movement
Rules that may limit the movement
–

One must serve the tennis ball within an area on the
baseline
Implements or machines
–
Using a walker, using weight machines, using a ball
Attractor States

Systems prefer states of stability

When a change in constraints is imposed on a
system, its stability is endangered

Deep basins = stable systems = difficult to
change

Shallow basins = less stable = more susceptible
to change
Phase Shifts

Changes in behavior are the result of a series
of shifts

Control parameters
–

Variables that move the system into new attractor
states: gaining leg strength to perform a skill better
Rate limiters
–
Constraints that function to hinder or hold back the
ability of a system to change :Adult learner, fear
So what happens when a skill
performance needs to change?

Practice strategies need to create instability in
a deep attractor basin
–
–

As the skill moves through the phase shift, it will
become a combination of the old and new ways
At some point it will be neither the old or new and
performance effectiveness is reduced
Eventually through practice, a new attractor
state is formed, and eventually a new deep
basin
Key Point

Movement patterns prefer state of stability

New movements self-organize and emerge
with phase shifts where attractors stabilize and
destabilize as a function of the control
parameters
Practical Application

Explain how orthotics function from a dynamic
system perspective
Exit Slip

How do the recall and recognition schema
work together?

How are phase shifts indicative of behavioral
change?