Motor Learning and Control

• Defining learning and control

• Measurement Schemes

• Open vs. Closed loop control

• Stages of Learning

• The role of practice– Amount– Composition – Scheduling

Motor Control

Understanding the execution of the events (physiological or behavorial/psychological description) that lead to skilled human movement

• How do we control how much force we produce ?

• What aspects of a movement are remembered to help recall a movement ?

Motor Control: Questions

# of motor units rate coding

spatial location effector used Psychological level

Physiological level

Motor Learning

involves changes in the execution of the events (physiological or behavioral/ psychological description) that lead to improvements (skilled) human movement

• Can we become more efficient in the way we produce force?

Can we recruit motor units differently with practice?

Can we use different frequency to recruit units?

Do we change the manner in which we remember a movement ?

Do we use different information about movement to remember it change (spatial features of movement followed by motor features (flexion-extension)

Motor Learning: Questions

Motor Development

study of changes in human movement behavior across the lifespan and the influence of these changes on human motor performance (p. 238) –

We will get to this in a later section

Measuring Motor Control

• Latency Measurements– Reaction Time

• assessment of planning operations that contribute to organizing/planning a movement

– Movement Time• assessment of movement implementation

Measuring Motor Control

• Error Measures– Absolute Error

• absolute deviation from a target

– Constant Error• movement bias

– Variable Error• movement variability

Measuring Motor Control

• Movement Quality– Kinematics

– Kinetics

– Electromyography

Position, velocity, acceleration, jerk (see biomechanics)

Force, torque (see biomechanics)

Controlling Movement

• Open-Loop (memory-driven)movements are completely pre-planned and

subsequent feedback during the movement doesn’t change the nature of the plan (e.g., traffic lights)

Using Reaction Time to examine movement planning

Warning “GO” Initiation Termination

foreperiod RT MT

Sternberg’s (1969) planning model

Perception Decision Motor PlanI O

Reaction Time

Perception: SRT

F F F F FF E F F FF F F F FF F F F F

O O O O OO E O O OO O O O OO O O O O

YES NO YES NO

Plot reaction time for simple and complex perceptual cases

Perception in Real World

Decision-making: CRT

Decision-making: CRT

0

50

100

150

200

250

300

One Light Two Lights

RT

Choice impacted by Compatibility

Real World Compatibility Effects

Real World Compatibility Effects

Motor Plan: Movement Complexity

Say /ba/ when the circle changes color

Say /ba/ x 4 when circle changes color

Motor Plan: Movement Complexity

0

50

100

150

200

250

300

ba x 1 ba x 4

RT

RT in this case is time to start to say /ba/

Simplifying Movement Planning

• Using feedback or closed-loop processing

Closed-Loop Control: Evidence

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

150 250 350 450

Light Off

Light On

Keele and Posner (1968)Keele and Posner (1968)

Pro

port

ion o

f Targ

ets

mis

sed

Required Movement Time between Targets

Closed and Open-Loop Control

Perception Decision Motor PlanI O

Open

Closed

Fitts and Posner’s Stages of Learning

• Cognitive– high verbalization

• Associative– fine-tuning

• Autonomous– attention-free

Closed-loop

Open-loop

Distinguishing Performance from Learning

• Performance (or acquisition)

• Learning – retention of what is practiced– generalizibility of what is practiced

Transfer Paradigm

Acquisition Retention (transfer)

Importance of Practice: Anecdotal

• “It appears that the patient will require much more opportunity to practice if motor control is to improve” (Duncan, 1997).

• “Skill acquisition is impossible without practice” (Winstein, 1997).

• Practice is repetition without repetition (Bernstein, 1967).

• Practice problem-solving is more effective for learning than simply repeating the solution (Lee et al., 1994)

Importance of Practice

• Power law of practice: Practice Extent

• Composition and Scheduling of practice

Pre-practice considerations

• Pre-practice Considerations– motivation for learning– making the task seem important (rationale)– goal setting (see Fig 11.1 Schmidt & Lee)

• Verbal information (overused, Wulf & Weigelt, 1997)– perceptual presentations better than verbal

Verbal instructions can sometimes interfere (implicit learning)

DV:AmplitudeFrequency

IV:InstructionNo Instruction

Verbal instructions can sometimes interfere (implicit learning)

Change in RT with practice

Change in RT with practice

Power Law of Practice

• The power law of practice is a very general law in human cognition, and in particular in human learning. The higher the level of expertise and the time spent on the task, the more difficult it is to improve (principle of diminishing returns).

• Previous graphs reveal a typical example of data showing a power law (first graph). An interesting feature of the power law is that , when data are plotted by taking their logarithms, they are well fitted by a straight line. (second graph).

Can we make a practice trial more useful?

• Practice Composition– Practice Variability– Mental Practice– Part vs. Whole Practice

• Practice Scheduling– Practice Distribution– Contextual Interference

Practice Variability vs. Specificity

ACQ RET TRAN

Specificity AAAAAAAA A E

BBBBBBBBB B E

CCCCCCCCC C E

Variable AAABBBCCC ABC E

Practice Specificity or Variability?

Mental Practice

• Skill acquisition (?)

• Skill Maintenance (?)

• Arousal Regulation (√)

• Planning and event management (√)

• Stress Management (√)

Whole vs. Part Practice

• Nature of the Skill– task component interdependence

• Capability of Learner– beginners, low aptitude

• Organization of Parts– Segmentation (progressive part),

simplification, fractionation

Key for whole is Interdependence of Parts

Practice Distribution: Using Time

• How to best use 60 hours of training to maximize performance and learning? (e.g., 2-a-days)

1 hour

2 hour

1 Session 2 Session

12 weeks 6 weeks

6 weeks 3 weeks

Baddeley & Longman (1978)

Practice Schedule

# of hrs to learn keyboard

Number of hrs to type 80/min

1 hr / 1 session 34.9 55

1 hr / 2 session 43 75

2 hr / 1 session 43 67

2 hr / 2 session 49.7 80+

Correct # of Keystrokes as a function of practice distribution

Can this work with verbal material: Melton (1970)

Structuring Variability: Contextual Interference

ACQ RET TRAN

Specificity

AAAAAAAA A E

BBBBBBBBB B E

CCCCCCCCC C E

Variable 1

AAABBBCCC ABC E

Variable 2

ABCBCACAB ABC E

A practical Example : Badminton

Shea & Morgan (1979)

Contextual Interference: Applied Examples

• Baseball (Hall et al., 1994)

• Badminton (Goode & Magill, 1986; Lui, 1991)

• Volleyball (Bortoli et al., 1992)

• Pawlata Roll (Smith et al., 1995)

Motor Learning and Control

• Defining learning and control

• Measurement Schemes

• Open vs. Closed loop control

• Stages of Learning

• The role of practice– Amount– Composition – Scheduling