Chapter 3
Behavioral Theories of Motor
Control
Key Talking Points
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Skilled movement requires that the learner not only condense the available degrees of
freedom (coordination) but also control the resulting movement.
Two prominent theories―motor program theory and the dynamic system
theory―offer explanations of how movement is coordinated and controlled.
A generalized motor program is an abstract representation of a class of actions that
can be modified to yield various response outcomes.
Some elements of the generalized motor program (invariant features) are thought to
be relatively fixed from trial to trial, defining the motor program itself; others
(parameters) are more flexible, defining the program’s execution.
Parameters for a given situation are specified according to one’s schema, which is a
rule or relationship that is developed through practice and directs decision making.
The interaction of the learner, the task, and the environment in which the task is
performed is fundamental to the understanding and facilitation of motor skill
acquisition and performance.
Motor control is thought to be a function of both open- and closed-loop mechanisms,
where movements are planned in advance, initiated, and carried out with limited
modification, unless time permits the incorporation of response-produced feedback.
The dynamic system theory argues against the notion of a central command center
and suggests instead that movement emerges or self-organizes as a function of the
constraints imposed on the system at any given time.
Three categories of constraints have been identified: organismic, environmental, and
task.
According to the constraints-led approach, the learner searches through a range of
potential movement solutions for the optimal movement strategy that will satisfy the
imposed constraints.
The role of the practitioner is one of identifying and manipulating key constraints to
guide the learner’s search for optimal movement solutions.
Short Answer / Essay Questions
1.
Explain the degrees of freedom problem.
2.
What were the two inherent problems associated with the original notion of motor
programs? How did the proposition of the generalized motor program resolve these issues?
3.
Compare and contrast open skills and open loop systems.
4.
Compare and contrast the Schema Theory and the Dynamic System Theory.
5.
Name and explain two lines of evidence supporting the existence of generalized motor
programs.
6.
According to the Dynamical Systems Theory, three categories of constraints exist that can
impose changes on learning motor skills. List these categories and give an example of
each.
7.
Describe the perceptual-motor workspace.
8.
Explain the concept of a hands-off practitioner.
Web Resources
Visit the link listed below to learn about the latest in humanoid robotics. (For more, see page 52
of the text.)
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Download short videos of Honda’s ASIMO, a humanoid robot, in action; for
example, you can view a clip of the robot conducting a symphony orchestra.
http://world.honda.com/HDTV/ASIMO/ (Page 52)
 Key Words: Video, Technology
Check out the following website to learn about a backless, kneeling office chair designed to
accommodate the seated human body in an ergonomically optimal manner. (For more, see page
69 of the text.)

Review of the Balans chair:
www.officechairadvice.com/ergonomic/kneeling/reviews/balans-ergonomicchair.html (Page 69)
 Key Words: Article, Technology
Exploration Activities
Signature Analysis: Fixed versus Flexible Features
Note: This activity helps students see that some elements of the generalized motor
program (called invariant features) are relatively fixed from trial to trial, defining the
motor program itself, while others (called parameters) are more flexible and define the
program’s execution. (For more, see page 54.)
Using a blank sheet of lined paper, write your signature eight times, according to the following
instructions:
1.
2.
3.
4.
5.
6.
with your dominant hand
with your non-dominant hand
holding the pen or pencil in your mouth
holding the pen or pencil between your toes
pressing down very hard
pressing very softly
7.
8.
slowly, while maintaining legibility
quickly, while maintaining legibility
According to early motor program theories, each of these variations of your signature would
have its own separate motor program stored in memory. Those theories were modified to suggest
that the motor program is a more general representation of a class of actions and consists of both
elements that are relatively fixed and elements that can be modified.
Questions:
1. Which aspects of the above instructions and your corresponding responses were flexible
and defined how to execute the motor program?
2. Which aspects were relatively fixed from trial to trial?
Self-Organization
Note: This exercise is meant to demonstrate to students the Dynamic System Theory of
movement, which holds that movement patterns emerge or self-organize as a function of
the interacting variables of learner, environment, and task. (For more, see page 65.)
To demonstrate the concept of self-organization, perform the following activities over a 10 m
distance and then observe another person performing the same activities.
a. Walk at a normal pace wearing running shoes.
b. Walk at a normal pace wearing the running shoes on the opposite feet.
c. Walk at a normal pace wearing a pair of running shoes that are at least two sizes too
large.
d. Walk at a normal pace wearing a pair of running shoes that are at least two sizes too
small.
Questions:
1. Based on your experience and observations, discuss the concept of self-organization.
2. Speculate as to what changes you might see in someone’s gait pattern when the person is
(a) walking on ice, (b) walking on a sandy beach, and (c) walking across a log. Include
the concept of self-organization in your response.
Organismic, Environmental, and Task Constraints
Note: These three activities demonstrate three types of constraints. (For more, see pages
66–67 of the text.)
Organismic Constraints
Try to jump up and touch the ceiling. Were you able to do it? What organismic constraints
enabled you to accomplish this task or prevented you from doing so?
Can you do the splits? What organismic constraints enable you to perform the splits or prevent
you from doing so?
Environmental Constraints
Equipment Needed:
Two pieces of paper
A small fan
With the two pieces of paper, make two identical paper airplanes. Mark a
starting point on the ground to ensure the same starting position for each trial.
Place the fan perpendicular to the direction of throw, on your throwing side,
and approximately 3 meters in front of the starting line, as depicted at right.
Turn on the fan and throw your first plane straight ahead, so that it must pass
through the stream of air created by the fan. Note the resulting flight path.
Now, turn off the fan and throw your second plane using the same throwing
motion you used to throw the first plane. Again, note the resulting flight path.
What influence did the airstream that was produced by the fan have on the
flight path of the first airplane? The second? What adjustments would have to
be made to get the plane to land directly in front of you when the fan is turned
on?
Task Constraints
Equipment Needed:
One tennis ball or baseball
One partially deflated volleyball
One basketball
One large playground ball
Large open field or area
Using a mature overhand throwing pattern, throw the different balls as far as possible into the
open area. If possible, have a friend videotape each attempt.
Compare and contrast the attempts. How did each ball influence the distance of the throw? Did
you use the same techniques to throw each ball? What compensations did you make, and why?
Did any organismic constraints influence the task?
Answers to Selected Cerebral Challenges
DISCLAIMER
Because all learning situations involve a dynamic relationship among the learner, the task, and
the environment, many responses will depend on the assumptions the respondent made when
answering the question. Consequently, the answers provided are merely examples of possible
responses and do not necessarily reflect all possibilities.
Cerebral Challenge 3.2
1. The use of over-weight implements is a common training method for conditioning in many
sports. Throwers use heavier shots, discuses, and javelins than are normally used in
competition; pitchers throw heavier baseballs; and hitters swing heavier-than-normal bats.
Does this technique involve a manipulation of invariant features or parameters? Can you
think of a situation or condition where the use of over-weight implements could hinder the
development of correct technique? What signs might a practitioner look for to avoid this
problem?
Answer
Typically, this technique would involve the manipulation of parameters however, if the
implement is too heavy, a change in invariant features could occur which would hinder the
development of correct technique. Practitioners should look for a breakdown in the movement
pattern to avoid this problem.
2. Another training technique is to practice when the athlete is fatigued. Based on your
understanding of invariant features and parameters, is this a good idea? Why or why not?
Answer
Provided that the levels of fatigue induced remain light to moderate, this strategy could enhance
physical conditioning and performance in a game situation (Christina & Corcos). However, high
levels or prolonged fatigue can cause the learner to practice incorrect motor patterns, which will
have an adverse effect on learning if the boundaries of the generalized motor program are
exceeded.
Cerebral Challenge 3.3
A hockey coach uses the following teaching strategy. Having taught the slapshot and given the
athletes an opportunity to develop a basic understanding of the movement, Coach X gives her
players these instructions:
“Using the slapshot technique that we have been learning, perform the actions listed below from
each of these four locations:
Net
X
X
X
X
First, shoot the puck so that it misses the net to the right.
Second, shoot the puck so that it misses the net to the left.
Third, shoot the puck so that it goes in the net.”
Will this experience help or hinder the athletes’ technique development for the slapshot? Why or
why not? Use the schema theory to support your answers.
Answer
A fundamental prediction of Schmidt’s Schema Theory is that variable practice, where multiple
variations of a given task are practiced, will enhance the development of one’s schema. This, in
turn, will enhance a performer’s capability to accurately select the appropriate response
specifications or parameter values to accomplish a movement goal. This initial experience would
assist the learner in the development of a reference of correctness.
Cerebral Challenge 3.4
1. Compare and contrast open and closed skills with open- and closed-loop control systems.
Answer
Open and closed skills are classifications of motor skills based on the predictability of the
environment. Open and closed loop control systems describe how the movement system is
organized.
2. Provide an explanation for what transpires in the following videos, which are found at
www.geocities.com/i_am_pippy43/jumpsmash.html and
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=7749625.
Answer
Both videos demonstrate open loop control.
Cerebral Challenge 3.5
A good illustration of the difficulty we have in stopping a planned movement was provided by
Slater-Hammel (1960). Subjects were asked to lift their finger from a response key at the same
instant that the sweep hand of a clock they were watching passed over the number 8. However, if
the sweep hand stopped prior to reaching the 8, subjects were instructed to continue to press
down on the response key. Results showed that when the sweep hand was stopped less than 140
msec before reaching the target, subjects had a difficult time not lifting their finger. In most
cases, subjects could not stop the action of lifting their finger in trials where the sweep hand
stopped 50 to 100 msec before reaching the 8.
Can you think of other real-life examples where you start a movement and then recognize that
you shouldn’t do the movement you started, but have difficulty stopping? Describe one example.
Answer
Examples of responses:
 Continued typing or texting following an error
 Swinging at an off-speed pitch
Cerebral Challenge 3.6
Answer the following questions according to Schmidt’s schema theory:
1. You are coaching an athlete who has a major competition in three weeks. You have noticed a
fl aw in her performance. Should you correct the flaw? Why or why not? What questions
must you ask to help you make your decision?
Answer
The question that must first be asked is whether the correction of the flaw involves an invariant
feature or a parameter change. Corrections involving fundamental changes to the motor program
(invariant features) will require the development of a new program and are time consuming.
Correcting such errors three weeks before a major competition would not be recommended as
performance will be negatively affected. On the other hand, parameter errors can typically be
resolved relatively quickly and with little or no adverse effect on performance.
2. You are coaching an eighth-grade volleyball team and are receiving complaints about the
soreness in the players’ forearms from bumping the ball. To help the athletes, you decide to
let them wear wristbands on their forearms in practice. Is this a good idea? Why or why not?
Answer
Again the question to be asked is whether the strategy will influence invariant features or
parameters. In this case, the wristbands will likely absorb much of the force of the ball,
decreasing its rebound. As a result, the performer will likely adopt an exaggerated arm swing in
order to direct the ball to its target, potentially executing a pattern of movement that exceeds the
boundaries of the generalized motor program being developed
3. You are teaching a unit on basketball in middle school, specifically the free throw.
Unfortunately, there are 28 students in your class and only four baskets in your gymnasium.
In addition to the lack of baskets, there are only 10 functional basketballs. You remember
reading an article in college that encouraged you to be creative and use substitute equipment
to increase time on task. You come up with the idea to use playground balls in addition to the
basketballs, and to tape targets on the wall at the height of a normal basket. Are these good
ideas? Why or why not?
Answer
Provided that the substitute balls and targets do not change the invariant features of the motor
program, this is a good idea. The instructor will need to provide feedback to the students to
ensure the use of correct technique. To optimize this situation, learners should rotate between
using the criterion equipment and the substitute balls and targets.
Cerebral Challenge 3.9
Categorize each of the following as an organismic (O), environmental (E), or task (T)
constraint:
a. Height of the curb for an individual in a wheelchair
b. Catching a pop fly while looking into the sun
c. Poor flexibility
d. Taunting fans when trying to make a free throw
e. Using a regulation size football with 10-year-olds
f. Lack of motivation
Answer
a. Task
b. Environmental
c. Organismic
d. Environmental
e. Task
f. Organismic
Cerebral Challenge 3.10
1. Fear often serves as a rate limiter (a constraint that hinders the ability of the system to
change). In hurdling, for example, beginning learners are often afraid that they will not clear
the hurdle and will be injured. If you were teaching hurdles, what strategies would you use to
overcome this rate limiter? What other rate limiters might be involved? Discuss your answer
in terms of the dynamic system theory.
Answer
To overcome this rate limiter, the practitioner needs to reduce or eliminate the learner’s fear. One
method of accomplishing this would be to use rocker hurdles or training hurdles that are not
weighted and fall more easily when contacted. Using cones with a foam noodle serving as the
crossbar would also reduce the learner’s fear. A third method would be to cover the hurdle
crossbar with a foam hurdle guard.
2. Explain how orthotics function from a constraints perspective.
Answer
Orthotics are inserted into the shoe or integrated into the shoe’s design, conform to the feet, and
are designed to help correct any misalignments in the foot, improve a person's posture, or
alleviate any pain in the foot or leg. They constrain the movement capabilities or actions of the
foot.
3. Given what you have learned about dynamic systems, can the speed at which a sit-to-stand
transfer is executed influence performance? Fully explain your answer
Answer
Yes. A critical level of velocity is needed to generate enough momentum to overcome the
stability of the seated position.