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1
KNES 385
Motor Control & Learning
Prof John Jeka
What is this class??? Course Description: Physiological and cognitive bases for motor control and their applications to the acquisition of movement skills and understanding of movement disorders.
Basic Question
• HOW are motor skills learned and controlled??
This includes: • Execution of ‘simple’ movements
• Expert performance
• Infant motor ‘learning’ (i.e., learning to walk)
• Rehabilitation (i.e., stroke patient re-learning to walk)
Course Outline
Unit 1: Motor Learning Unit 2: Neurophysiology of Motor Control Unit 3: Theories of Motor Control Unit 4: Role of Memory / Attention
2
UNIT 1.1: Introduction to motor control, learning, skill and performance
Objectives
1. Define / compare and contrast: motor learning, control,
coordination, skill and ability • Name and describe the factors that influence the above terms?
2. Classify motor skills based on established criteria
3. Identify characteristics of skillful behavior
Some Early Definitions
As an area of study….
• Motor control – understanding how the neuromuscular system functions to activate and coordinate the muscles and limbs involved in the performance of a motor skill (Magill, 2007)
• Coordination – the patterning of body and limb motions relative to each other and to the environmental objects and events
• Three aspects / dimensions of control???
Some Early Definitions
As an area of study…..
• Motor learning – study of the processes involved in acquiring and refining motor skills that promote or inhibit that acquisition
Sample Questions… • What is the role of feedback in motor learning?
• What type of feedback enhances learning?
• How do practice schedules impact motor learning?
• What is the role of memory in motor learning? Coker, 2004
3
You have to go faster….
Skills, Movements and Abilities
What is Skill?
Write down a skill you think you possess
Do the answers vary?
Consider the many activities we perform on an everyday basis. We perform actions that we have acquired over time. From walking down steps to playing video games, these are skills.
A skill is an action or task that has a specific goal to achieve (Magill, 2001).
4
Are all activities skills?
An activity is a skill if it: 1) Is directed toward the attainment of a goal 2) Is performed voluntarily 3) Has been acquired by experience/
practice
What makes a skill a motor skill?
A motor skill requires voluntary body/limb movement (Magill, 2001).
Is the skill you wrote down a motor skill under these criteria?
Unless you thought of a cognitive skill, or one of the primary behaviors we are born with (i.e. suckling), it should be!
What about activities like…
sitting standing walking
Another conceptualization of skill is something which distinguishes competence between, for example, experts and novices.
vs.
Levels of Skillfulness
5
• In addition to the criteria for a movement to be considered a skill, there are additional characteristics of skilled performance
1. Adaptable
2. Consistent
3. Efficient
Levels of Skillfulness
What are Movements?
Movements are behavioral characteristics of specific limb(s) that are components of a skill (Magill, 2001)
i.e., movements are the building blocks of a skill
Why differentiate between skill, movement, etc?
There is a taxonomy or hierarchy (e.g., Biology: phylum – class – order – family etc…)
Goal
Skill
Movement
Put the ball in the basket
Jump shot, dunk, lay-up
Characteristics that vary within and between people Process
measures
outcome measures
6
Classifying skills
Why classify skills?
• Simplifies discussion
• Allows comparison across research
• Provides context for coaches/therapists
Hot Cold
A one-dimensional continuum is a range between two ‘ends’ on a given variable
Unlike biological classifications, we use a continuum so that a skill does not have to exactly match a condition or fit into a box on some chart… skills have high variation across many variables.
Stuff
Animal Vegetable Mineral
Classifying skills
Consider the 8 skills below
What characteristics do they have in common?
Which characteristics differentiate them?
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Commonalities All require concentration.
All must focus attention on a specific point/thing.
???
Differences Some have a stable, predictable environment in which the skill is
performed, some do not. Some use the whole body, some
just use the hands/arms. Some are continuous, some are
sporadic. Some involve fast movements,
some slow. Some involve standing posture,
some seated.
… Basis for continua.
Classifying skills
Classification 1: Size of musculature used
The prime movers used in surgery and long jumping are clearly not the same.
Use large musculature; involve less movement precision Fundamental motor skills (jumping, locomotion, etc…)
Require control of small muscles; hand-eye coordination Writing, typing, sewing, etc…
GROSS FINE
≠
Classification 2: Type of Movement
Discrete Serial Continuous
Have a clearly specified beginning and end (e.g., hitting a switch) – one movement skills.
Involve a series of discrete movements (e.g., playing piano, hammering a nail)
Have arbitrary start and end (e.g., swimming)
Implications for analysis
??
8
Classification 3: Motor-cognitive dimension
Low cognitive Moderate cognitive High cognitive demand demand demand
Actions are automatic, with little thinking about task required
The motor component is less significant than the cognitive element
Classification 4: Stability of the environment
Environment refers to the characteristics of objects/people the skill is performed with
Closed Open Environment does not change while performing the skill. These tend to be self-paced; the object ‘waits for your action’.
Environment is changing during performance of the skill. These are usually not self-paced, require constant adjustment.
Gross or Fine motor skill? Order the following skills in terms of the size of musculature used in the action.
Punching a speed bag Typing your name Getting out of your car
Open or Closed motor skill? Order the following skills in terms of the environment the skill is performed in.
Snapping a football Basketball jump shot Bowling
Classifying skills
9
So how does Skill relate to Ability?
An ability is a stable trait or capacity of the individual that is a determinant of a person’s potential for the performance of specific skills (Magill, 2001).
Abilities are generally thought to be hereditary/genetically determined, and by large unmodified by experience (Schmidt & Wrisberg, 2000).
The hardware people bring to a task.
Ability
INDIVIDUAL DIFFERENCES
Stable, enduring differences among people that contribute to differences in task performance (Schmidt & Wrisberg, 2000)
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INDIVIDUAL DIFFERENCES
Body type Abilities
Cultural background Emotional
make-up
Developmental Stage
INDIVIDUAL DIFFERENCES
Body type Abilities
Cultural background Emotional
make-up
Developmental Stage
ABILITIES SKILLS
Stable Modified by practice
Inherited traits Developed
Few in number Many in number
(Schmidt & Wrisberg, 2000)
Underlie performance Depend on different of many skills subsets of abilities
Abilities vs. Skills
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Abilities are highly related and can be characterized by a single, global ability (Brace, 1927; McCloy, 1934)
- Minimal empirical evidence
=
Generalized Motor Ability???
Abilities are relatively independent. The ‘all-around’ athlete has a high number of abilities (Henry, 1958)
Research evidence for specificity of motor abilities
Correlation ≠
Specificity of Motor Ability???
Rehabilitation
Identifying abilities allows the practitioner to get to the source of a problem. This can be achieved via a task analysis.
May identify areas for compensation.
12
Skill or Ability?
Skill or Ability?
Skill or Ability?
13
Skill or Ability?
Hall of Shame???
Preparing for a career in professional sports is risky business because it requires focusing on getting a job that statistically, does not exist.
Skill or Ability?
UNIT 1.1 : Introduction to motor control, learning, skill and performance
Objectives
1. Define / compare and contrast: motor learning, control,
coordination, skill and ability • Name and describe the factors that influence the above terms?
2. Classify motor skills based on established criteria
3. Identify characteristics of skillful behavior
1
Measurement and Evaluation Of Performance
Unit 1.2
Prof. John Jeka
Unit 1.1 Outline 1.1 Introduction to Motor Control and Learning
a) Motor coordination vs. motor control vs. motor learning
b) Motor skills and abilities
c) Classification of motor skills
d) Characteristics of skillful performance
1.2 Assessment of Motor Skill Performance
a) Outcome Measures (i.e., error scores, timing, etc.)
b) Process Measures (i.e., kinematics, kinetics, brain imaging, etc.)
1.3 Motor Learning
a) Characteristics of the learning process
b) Assessment of motor learning
c) Learning stages
1.4 Effects of practice on motor learning
1.5 Assisting the Learning Process
a) Observational learning
b) Augmented feedback
In order to:
• understand skilled performance….
• infer learning ….
• compare individuals/groups …
We must measure performance
2
Objectives
1. Compute, utilize, and interpret outcome and process
measures used to assess motor control, coordination, and learning
2. Design a research experiment to examine specific research questions in motor control and learning.
UNIT 1.2: Measurement and Evaluation of Performance
Motor Performance
Motor performance is what we actually measure when a person performs a skill. It is divided into 2 types of measure:
Performance outcome measures (outcome scores)
Performance production measures (process measures)
What is Motor Performance???
Indicate the outcome of performing a skill, such as:
How accurate was a shot/throw etc? …ACCURACY
How fast did a person move? …TIME/SPEED
How far did an object travel? …MAGNITUDE
Outcome Measures
3
Measures of Accuracy: Error Scores
Why measure error? Accuracy is a major component of human skill from everyday tasks to sports performance. The way in which we understand the accuracy of performance is simply to measure the extent to which performance differed from a criterion.
How do we measure error? The criterion can be a specific target in space, such as an archery target or a time, such as matching a rhythm.
1 Dimension 3 Dimensions
X axis
Y ax
is
Z axis X axis
Y ax
is
X axis
2 Dimensions
Dimensionality of Error Scores
A dichotomy (hit/miss): This performance has 6 hits/4 misses (60%).
So does this!
Is there a difference in the quality of performance?
Information Obtained from Error Scores
4
10
8
6
4
28 points
Only 40% hit
28 points
60% hit
Information Obtained from Error Scores
The absolute difference in relevant units between the criterion and the performance outcome
abs (xi – T) Absolute Error (AE) describes the error along a single dimension
We take multiple trials to gain a representative measure of performance…the average.
AE = ∑ abs (xi – T) n
Where:
• ∑ = the sum of
• T = target
• n = number of trials
Absolute Error (AE)
0 10
Target
x1 x2
x3
11 9 AE = ∑ abs (Xi – T)
n
Σ 2.5
AE = 0.833
Trial Xi Abs Xi-T = 1 11 11-10 1 2 9 9-10 1 3 9.5 9.5-10 0.5
Absolute Error (AE)
Then divide by “n”
the number of trials
5
What skill might this be appropriate for?
• Absolute error for two dimensional tasks
Radial Error (RE)
RE = Errorx2 + Errory
2
X axis
Y axis
Target
c
a
b
Radial Error (RE)
RE = Errorx2 + Errory
2
c2 = a2 + b2
c = a2 + b2
Pythagorean Theorem
RE = Errorx2 + Errory
2
X axis
Y axis
a
b
c d
Point X-axis
Y-axis
a 3 3 b -3 1 c -1 -3 d 2 -2
Radial Error (RE)
6
RE = (x-axis error)2 + (y-axis error)2
Point X-axis
Y-axis
a 3 3 b -3 1 c -1 -3 d 2 -2
X2 Y2
9 9 9 1 1 9 4 4
X2+Y2 sqrt
18 4.24 10 3.16 10 3.16 8 2.83 ∑ 13.39
/ n 3.35 Average RE
• Absolute measures of accuracy may hold insufficient information. For example, they fail describe tendencies to over or under shoot.
• Constant error (CE): represents magnitude of error in a specific direction (i.e., it is no longer absolute).
CE = ∑ (xi – T)
0 10 ft
Target
Error
AE = ∑ abs (xi – T) … “you missed by that much” Vs.
CE = ∑ (xi – T) … “you overshot by that much”
Bias in Performance Outcomes
0 10
Target
x1 x2
x3
11 9 CE = ∑ (Xi – T)
n
Trial Xi Xi-T = 1 11 11-10 1 2 9 9-10 -1 3 9.5 9.5-10 -0.5
Constant Error (CE)
Σ -0.5
Then divide by “n”
the number of trials
CE = -0.167
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• Variability is a measure of consistency in performance. The typical measure is the standard deviation (Std Dev).
• Variable error (VE) is an index of how much variability there is in the accuracy of performance.
Where:
∑ = the sum of x = the individual score m = the mean n = the sample size
∑ (x-m)2
Std Dev =
n - 1
Variability in Performance Outcomes
Std Dev = ∑ (x-m)2
n - 1
1
4
5 2
3
Trial 1 1.5 Trial 2 0.25 Trial 3 0.25 Trial 4 3 Trial 5 0.5
Variable Error (Std Dev)
Variable Error (Std Dev)
Std Dev = ∑ (x-m)2
n - 1
Trials Error (x – m) (x – m)2
1 1.5 0.16 2 0.25 -0.85 0.7225 3 0.25 -0.85 0.7225 4 3 1.9 3.61 5 0.5 -0.6 0.36
Mean 1.1 Sum 5.5 5.5775
5.5
8
Variable Error (Std Dev)
Std Dev = ∑ (x-m)2
n - 1
Trials Error (x – m) (x – m)2
1 1.5 0.4 0.16 2 0.25 -0.85 0.7225 3 0.25 -0.85 0.7225 4 3 1.9 3.61 5 0.5 -0.6 0.36
Mean 1.1 Sum 5.5 5.5775
5.5
Variable Error (Std Dev)
Std Dev = ∑ (x-m)2
n - 1
Trials Error (x – m) (x – m)2
1 1.5 0.4 0.16 2 0.25 -0.85 0.7225 3 0.25 -0.85 0.7225 4 3 1.9 3.61 5 0.5 -0.6 0.36
Mean 1.1 Sum 5.5
Std Dev 1.181
5.5775
5.5
(A) (B) Which would be regarded as most skilled?
(A) has a lower AE & lower CE, but a higher VE than (B).
(B) has a higher AE & higher CE, but a lower VE than (A)
Skilled Performance??
9
Root mean square error (RMSE)
• Error between a participant’s displacement (position) curve and a criterion (ideal) curve
• Computes one error score for the total duration of the task
Continuous Skills
Dichotomy hit/miss Zones of accuracy Absolute error (AE)
Radial Error (RE) Constant error (CE) Variable error (VE)
RMSE
Magnitude Accuracy Time/speed
Performance Outcome Measures
• Reaction time (RT): interval between the onset of a signal or stimulus, to the initiation of a response
Stimulus or
‘Go’ signal
Light/Color
Word/Sound
Shock/Vibration
Vision
Hearing
Touch
Speed: Reaction and Movement Time
10
Stimulus
Simple RT
Response key
Index Index Middle Ring Index
Used in information processing studies
Reaction Time
Choice RT Discrimination RT
Simple RT
Choice RT
Discrimination RT
Match the following
Reaction Time
Simple RT:
Choice RT: # of choices 1 2 3 4 5 6 7 8 9 10
~RT (ms) 200 350 400 450 500 550 600 600 650 650
Damon et al. (1966)
Light 240 ms Siren 220 ms
Electrical shock 210 ms All together 180 ms
Swink (1966)
What are typical RT values?
11
• Reaction time (RT): the interval of time from the onset of a ‘go’ signal or stimulus to the initiation of a response
• Movement time (MT): the interval from the initiation of the response to the completion of the movement.
• Response time: the sum of RT + MT. From the onset of a ‘go’ stimulus to the completion of the movement.
These are all defined by observable events
Performance Measures: Time
• EMG, which indicates electrical activity of muscle, has been used to separate RT into central and peripheral components.
Electromyography (EMG) in RT measures
• Research shows that following presentation of a stimulus, for a portion of RT, there is no electrical activity. This 40-80 ms period is known as pre-motor RT represents CENTRAL PROCESSES (decision making/perceptual processes etc). Weiss, 1965
EMG
Response time
Foreperiod RT MT
Pre-motor Motor
Electromyography (EMG) in RT measures
Warning Stimulus Presentation
Movement Onset
Movement Offset
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Indicate the ‘size’ of an outcome, and have particular relevance in sports settings.
Distance
How far you throw
Weight
How much you lift
Height
How high you jump
Measures of Magnitude
Dichotomy hit/miss Zones of accuracy
Absolute error Constant error Variable error
RMSE
Magnitude Accuracy Time/speed
Reaction Time Movement Time Response Time
Distance Height Weight
Performance Outcome Measures
• Outcome measures do not tell us how a result was achieved. To understand what underlies performance, we need process measures
Kinematics
Kinetics EMG
Brain activity/imaging
Performance Process Measures
13
• Measures which describe motion, without regard to the cause of that motion.
• Muybridge (1878) in California, was the first to capture serial images of fast animal motion.
Kinematics
• Modern systems such as Optotrak use infra-red technology to relay the spatio-temporal positions of markers. 3-D Data can be captured at 1000 Hz.
Kinematics
Video/film Optoelectric
Slow sampling rate Fast sampling rate
Wide workspace of data collection Narrower workspace (less as Hz increases)
Variation in precision of measurement Very precise
Forgiving (extrapolation) Less forgiving
Inexpensive Expensive
Schmidt & Lee (1999)
Kinematics
14
Both methods provide raw data in the form of x, y, and z coordinates. From this we can calculate the following:
Displacement (linear/angular)
Velocity (linear/angular)
Acceleration (linear/angular)
Coordination (relative motion)
3 Dimensions
X axis
Y ax
is
Z axis
Kinematics
Motion Analysis
Motion Analysis
15
• Change in spatial position
Displacement
Time (s) Disp (m) Velocity (m/s)
Accel (m/s^2)
0 0
4.1 20
7.9 40
11.9 60
15.7 80
19.8 100
24.1 120
28.1 140
32.1 160
35.8 180
40.0 200
Displacement
0
50
100
150
200
250
0 5 10 15 20 25 30 35 40 45
Time (s)
Dis
plac
emen
t (m
)
• the rate of change in position (displacement)
Velocity
v = Δdisplacement
Δtime
Time (s) Disp (m) Velocity (m/s)
Accel (m/s^2)
0 0
4.1 20
7.9 40
11.9 60
15.7 80
19.8 100
24.1 120
28.1 140
32.1 160
35.8 180
40.0 200
v = 4.1 – 0s
20 – 0 m
v = 4.88 m/s
• the rate of change in position (displacement)
Velocity
v = Δdisplacement
Δtime
v = 4.1 – 0s
20 – 0 m
v = 4.88 m/s
Time (s) Disp (m) Velocity (m/s)
Accel (m/s^2)
0 0 4.88
4.1 20 5.29
7.9 40 5.02
11.9 60 5.22
15.7 80 4.91
19.8 100 4.61
24.1 120 5.06
28.1 140 4.88
32.1 160 5.43
35.8 180 4.76
40.0 200 N/A
Velocity
0
1
2
3
4
5
6
7
0 5 10 15 20 25 30 35 40
Time (s)
Velo
city
(m/s
)
16
• the rate of change in velocity
Acceleration
a = Δvelocity
Δtime
a = 4.1 – 0s
5.29 - 4.88 m/s
a = 0.1 m/s^2
Time (s) Disp (m) Velocity (m/s)
Accel (m/s^2)
0 0 4.88
4.1 20 5.29
7.9 40 5.02
11.9 60 5.22
15.7 80 4.91
19.8 100 4.61
24.1 120 5.06
28.1 140 4.88
32.1 160 5.43
35.8 180 4.76
40.0 200 N/A
• the rate of change in velocity
Acceleration
a = Δvelocity
Δtime
Time (s) Disp (m) Velocity (m/s)
Accel (m/s^2)
0 0 4.88 0.10
4.1 20 5.29 -0.07
7.9 40 5.02 0.05
11.9 60 5.22 -0.08
15.7 80 4.91 -0.07
19.8 100 4.61 0.10
24.1 120 5.06 -0.05
28.1 140 4.88 0.13
32.1 160 5.43 -0.18
35.8 180 4.76 N/A
40.0 200 N/A N/A
a = 4.1 – 0s
5.29 - 4.88 m/s
a = 0.1 m/s^2
Acceleration
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 5 10 15 20 25 30 35
Time (s)
Acc
eler
atio
n (m
/s^2
)
Upright Stance Hip Pattern Ankle Pattern
Coordination • Relative motion is the motion of one segment or point in a
configuration relative to another • Postural coordination patterns
17
ITO = ipsilateral take-off IFS = ipsilateral foot-strike CTO = contralateral take-off CFS = contralateral foot strike
Enoka et al. (1978)
Intra-limb Coordination: Running
• Measurements of the forces which cause motion. • Predominantly apply Newton’s laws of motion.
• Examples: • Force: push or pull on an object; product of an object’s mass
and acceleration (e.g., ground reaction force)
• Torque: angular force directed around an axis of rotation; product of force and perpendicular distance to the axis
• Momentum: product of an object’s mass and velocity
• Equipment includes force platforms, strain gauges, etc.
Kinetics
Kinetics: Force Platform
18
Electrodes detect electrical activity which result in muscular contraction. Electrical signals are amplified and recorded.
Data describes temporal patterning, and amplitude.
• Measures the electrical activity in muscle. Electrodes are attached to the skin superficial to the muscle belly
Electromyography (EMG)
Brain activity and
Imaging
STUDYING THE LIVING BRAIN
• Electrodes placed on skull detect and record ‘brainwaves’, or the electrical patterns created by the rhythmic oscillations of neurons.
• Technique often uses: – Event related potentials (ERPs): electrical peaks that are related
to a specific stimulus.
– Coherence- functional communication between brain areas of interest
Electroencephalography (EEG)
19
• Electrodes placed on skull detect and record ‘brainwaves’, or the electrical patterns created by the rhythmic oscillations of neurons.
Electroencephalography (EEG)
Pros: Directly measure brain activation Good temporal Resolution Relatively cheap Easy to transport Silent! Easy to use for MANY behavioral paradigm
and with different populations
Cons: Spatial resolution Set-up time
Electroencephalography (EEG)
• Uses computed tomography (CT) and radioactive markers injected in the bloodstream.
• Identifies areas of brain working most based on ‘fuel intake’ (i.e., glucose and O2 providing energy to firing neurons).
Positron Emission Tomography (PET)
• Characteristics: Good spatial resolution; poor temporal resolution
20
• Records the magnetic fields produced by the electrical activity of the brain.
Magnetoencephalography (MEG)
• Characteristics: Better spatial resolution; good temporal resolution
Pros: Magnetic fields are less
distorted Excellent temporal resolution Reference-Free Less set-up time Direct measure of brain
activation
Cons: Orientation of MEG Less readily available
Magnetoencephalography (MEG)
• Aligns atomic particles in tissues by magnetism, then ‘bombards’ them with radiowaves. Different tissues return different radio signals. fMRI determines areas in brain where there is most oxygenated hemoglobin.
Functional Magnetic Resonance Imaging (fMRI)
• Characteristics: Good spatial resolution; poor temporal resolution
21
Pros: Excellent spatial resolution
Cons: Indirect measure of brain
activity Susceptible to movement
artifacts Use of templates and
atlases
Functional Magnetic Resonance Imaging (fMRI)
Brain Imaging
Spa
tial R
esol
utio
n H
igh
Res
olut
ion
Low
Res
olut
ion
Low Resolution Temporal Resolution
Human Connectome
22
Summary of Performance Measures
Outcome Accuracy Error scores
- Absoluter error (1-D) - Radial error (2-D) - Constant error - Variable error
Movement Speed Reaction time
- simple - choice - discrimination
Movement time Response time Magnitude
Process
Description of movement Kinematics
- displacement - velocity - acceleration - relative motion - phase plane portraits
Forces underlying movement Kinetics
- force - torque - moment
Electrical activity of muscle EMG Brain activity/images EEG, PET, fMRI & MEG
But before you start measuring performance…..
Is it an objective measure?
A measure is objective if it can be employed consistently by different people. It is also objective if the measurement scale is appropriate.
Is it a valid measure?
This refers to whether a test measures what it is supposed to measure. Does your measure have construct validity? Magnitude measures almost always do. However, is accuracy, consistency, bias a construct of your skill?
Is it a reliable measure?
Is the measurement repeatable? Deviations in the way a test is performed can result in markedly different results. As a result, change may be incorrectly attributed to difference in performance.
Improving your tests’ objectivity, reliability, and validity
• Consider the purpose of the skill
• Keep the test environment consistent
• Document your methodology
• Standardize measures
• Don’t test yourself!
23
Step 1
• Develop a testable research question
Step 2
• Formulate hypotheses – what is the anticipated outcome and why?
Scientific Method
Step 3
• Operationally define independent and dependent variables
– Independent : the ‘manipulated’ variables/factors
– Dependent: the measured variable (presumably influenced by the independent variable(s))
Scientific Method
Step 4
• Design study to test research question
M F
1 2 3 4
Subjects….? Who… How many? Independent groups or repeated measures? # of trials? How will you control for extraneous variables?
Scientific Method
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Step 5
• Observe behavior and gather data Male Female
SUB 1 12 11
SUB 2 16 14
SUB 3 21 12
SUB 4 22 17
SUB 5 16 12
SUB 6 16 16
SUB 7 14 11
SUB 8 25 21
SUB 9 22 17
SUB 10 34 26
SUB 11 12 11
Scientific Method
Step 6
• Analyze and interpret results of study
• Run descriptive statistics (and inferential statistics)
Male Female
SUB 1 12 11
SUB 2 16 14
SUB 3 21 12
SUB 4 22 17
SUB 5 16 12
SUB 6 16 16
SUB 7 14 11
SUB 8 25 21
SUB 9 22 17
SUB 10 34 26
SUB 11 12 11
MEAN 19.09091 15.27273
SD 6.579583 4.818525
Scientific Method
Objectives
1. Compute, utilize, and interpret outcome and process
measures used to assess motor control, coordination, and learning
2. Design a research experiment to examine specific research questions in motor control and learning.
UNIT 1.2: Measurement and Evaluation of Performance
7/4/12
1
Introduction to Motor Learning
Unit 1.3
Prof. John Jeka
Unit 1 Outline
1.1 Introduction to Motor Control and Learning
1.2 Assessment of Motor Skill Performance
1.3 Motor Learning
• Characteristics of the learning process
• Assessment of motor learning
• Learning stages
1.4 Effects of practice on motor learning
1.5 Assisting the Learning Process
Objectives
1. Define and distinguish between motor performance and learning
2. Identify key characteristics of the learning process
3. Describe and compare / contrast different methods to assess motor learning
4. Design research experiments to assess motor learning
5. Describe and compare / contrast different stages of motor learning
UNIT 1.3: Introduction to Motor Learning
7/4/12
2
Although we are born with the neural structures which facilitate the acquisition of knowledge and skill, with the exception of elementary reflexes, infants are born without repertoires of behaviour
Bandura (1977) !
Complex human behaviours acquired over time and development are the result of experience and observation. In essence, they are learned. "
Introduction to Motor Learning!
Understanding Learning
Learning is a relatively permanent change in the capability to perform a skill
Learning cannot be directly measured – it is inferred from performance!
Observable behavior Temporary
Not necessarily a result of practice
Influenced by performance variables
• refers to a change in the potential or capability to perform a behaviour ….why?
Learning
7/4/12
3
Characteristics of the learning process
1. Performance of skills shows an improvement over a period of time
Characteristics of the learning process
2. Performance becomes more consistent (less variable) over time
0 5 10 15 20 25 30 35 40 0
0.2
0.4
0.6
0.8
1
1.2
1.4
Varia
bilit
y
Blocks of Trials
3. There is greater persistence in the improvements made
Practice"Time delay"
Repeat"
Characteristics of the learning process
Krakauer et al., 2005: Visuomotor adaptation
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4. Performance of the skill becomes more adaptable !
Characteristics of the learning process
Performance Curves
…are a method of assessing learning by recording levels of performance across practice
time (or time period)"
Perfo
rman
ce
mea
sure"
Learning a new skill is typically characterized by one of four performance curves
Dependent variable for learning
e.g., absolute error, variable error, time-on-task, RT
Linear Negatively accelerated
Positively accelerated
S-shaped
(ceiling effect)
(ceiling effect)
Performance Curves
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Performance Curves in Kinematics
More complicated as they show not only changes in performance between trials, but within trials "
Improvement in performance can be assessed by how close the movement pattern matches the criterion.
Consistency can be assessed by the extent to which the movement patterns vary.
It is not wise to infer learning from practice because:
Practice data provides no evidence for permanent/semi-permanent changes in behavior
Performance during practice is susceptible to over-estimating and under-estimating learning
Performance in practice may temporarily plateau
150160170180190200210220230
1 2 3 4 5 6 7 8 9
Days of practice
Abs
olut
e er
ror
Assessment of Learning
Assessing Learning by Retention
The typical design is as follows:
Pre-test Practice/acquisition Post-test Retention test
Measures ability to
perform task before the treatment
+ 1 to 7 days
Measures ability to
perform task after period of
practice
Measures ability to perform task
after a no-practice retention interval
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Pre-test Practice/acquisition Post-test Retention test
Effect of practice on performance
Learning
Decay of performance
Assessing Learning by Retention
Experimenters may test several groups using the same design
Pre Post Retention
3 x 3 design
Control
Verbal Guidance
Video Model
Assessing Learning by Transfer
• Transfer of learning describes how previous practice on a task influences the learning of a new skill
Transfer can be…
…negative, where previous practice of one skill hinders learning of a new skill
…or positive, where previous practice in one skill assists learning of a new skill
Positive Transfer
• Sensorimotor adaptation experiment (Abeele & Bock, 2003)
• Group A (left) performed tracking task in rotated environment before the pointing task (vice versa for Group B)
• Group A smaller errors on pointing task compared to Group B (right) – Positive transfer across the tasks!!!!
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Negative Transfer
• Sensorimotor adaptation experiment (Caithness et al., 2004)
• Task A = 30° CCW rotation; Task B = 30° CW rotation
• Angular error on day 2 (task B) exceeded -30 degrees, suggesting that performance on Task A hindered performance on Task B
• Negative transfer!!
The significance of transfer
1. It can define the appropriate sequencing of skills to be learned
• Curricula tend to be organized in a simple-to-complex order
• Early fundamentals need to be in place before moving on
• Skill classifications can be a useful tool to guide transfer
• PT’s need an appropriate order of functional treatment
2. It can assess the effectiveness of practice conditions!
Criterion performance"
Practice condition 1"
Practice condition 2"
Practice condition 3"
The significance of transfer
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Theoretical explanations for positive transfer of learning
Identical elements theory (Thorndike, 1914)
Task 1 Task 2 Task 3 Task 4
Little overlap of elements = little transfer
Greater overlap of elements = greater transfer
Transfer-appropriate processing theory
Suggests that movement components need not be similar.
Instead, positive transfer is more likely between two skills or practice conditions which share cognitive processing characteristics
(Morris et al, 1977)
Research designs to assess positive transfer
Experimental Practice skill A Perform skill B
Control No practice Perform skill B
Experimental Skill in context 1 Skill in context 2
Control No practice Skill in context 2
Group Practice conditions Transfer test
Experimental group – control group Percentage of transfer = x 100
Experimental group + control group
OR"
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Contextual variations in transfer tests
Changes to the physical environment
Changes in availability of feedback information
Changes to learner’s personal characteristics
Novel skill variations in transfer tests
Changes to the task itself (e.g., faster/slower)
i.e., Changes in constraints!
Transfer
Mobility Simulator
• The devices can apply 6DOF forces and torques to the feet
• Simulate varied support surface conditions. The platforms are integrated with two VE simulations, a street crossing and park path.
http://shrp.umdnj.edu/rivers/facilities/index.htm
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Nintendo Wii
• Use of Wii in physical rehab settings (children with cerebral palsy)
Deutsch et al., 2008
Stages of Learning
Fitts & Posner (1967) 3-stage model
Practice time continuum
Cognitive stage Associative stage Autonomous stage Learner encounters cognitive problems, and must integrate information.
What should I do? How should I move? Large errors; variability
Learner makes associations b/w environmental cues and movements.
Learner detects errors. Performance is refined, variability and error decreases.
Learner performs skill in habitual or automatic manner. No conscious thought of action processes. Learner can divide attention.
Gentile’s two-stage model (1972, 2000)
Stage 1: Getting the idea of the movement
The learner organizes a movement pattern – by delimiting the potential muscular responses in tune with the demands of the environment.
Regulatory conditions Environmental features which specify how movement must be performed
Must discriminate
Non-regulatory conditions Environmental conditions which do not influence movement characteristics.
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Stage 1 also is highly cognitive – problem solving
Learner ‘leaves’ stage 1 with a framework for the organization of the movement, but performance is variable and inefficient
Stage 2: Fixation/diversification
Learner must acquire - adaptability for the skill consistency economy of effort
Gentile’s two-stage model (1972, 2000)
Closed Open
Skills require fixation
Learner must refine pattern for consistency.
Skills require diversification
Learner must diversify the basic movement pattern. Must be highly tuned to the regulatory conditions
Gentile’s two-stage model (1972, 2000)
…of coordination, control and skill (Newell, 1985)
Toward skill coordination
control
Early skill learning – emphasis within the synergy of coordination and control is upon assembling a new movement pattern (coordination)
Later in skill learning, when the movement pattern is assembled, the emphasis is upon scaling the movement pattern (control)
Embedded Hierarchy…
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Bernstein’s Degrees of Freedom
The degrees of freedom (DOF) in any system is the number of independent elements to be controlled
DOF problem: how can a complex system act to constrain so many degrees of freedom into a functional unit?
e.g., The human arm has 7 degrees of freedom"
3 at the shoulder"
1 at the elbow"
1 at radioulnar joint"
2 at the wrist"
Early learning – novice simplifies movement by “freezing” a portion of available DOF. Later learning – there is a release of the DOF. Dynamics of action become more apparent to the learner Expert - release and organization of DOF. Flexibility to freeze or release DOF at appropriate moments
Bernstein’s Degrees of Freedom
Objectives
1. Define and distinguish between motor performance and learning
2. Identify key characteristics of the learning process
3. Describe and compare / contrast different methods to assess motor learning
4. Design research experiments to assess motor learning
5. Describe and compare / contrast different stages of motor learning
UNIT 1.3: Introduction to Motor Learning
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Role of Memory in Motor Control and Learning
Unit 4.1
Prof. John Jeka
Objectives
1. Define / compare and contrast: verbal and motor memory, declarative and procedural memory, short- and long-term memory
2. Describe methods used to assess memory
3. Explain the neurophysiological processes underlying memory
4. Describe different ‘causes’ of forgetting
UNIT 4.1: Role of Memory in Motor Control and Learning
Information processing does not simply refer to generating short-term responses.
Information must be retained, and accessed later.
In what form are memories stored?
??
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Memory
How is that I can remember the names of every teacher I had in school (Mrs. Bungay, Mrs. Abel, Mr. Jones, Miss Waugh, Miss. Wilson, Mr. Jones II, Mrs. Winterbottom, Mr. Robottom, Mr. Cormack, Mr. Dean, Mrs. Court… etc , etc)…
But I forget a name within 5 minutes of meeting someone new?
Why does repetition and association make it easier to remember something?
Why are phone numbers 7 digits?
Is memory for action the same as memory for numbers, language etc?
Memory
- The internal record or representation of some prior event or experience
- Retention of experience-dependent changes over time
- The capacity to remember
- Tulving (1985): ‘the capacity that permits the organism to benefit from past experiences’
Memory Some definitions…………….
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Schmidt & Lee (1999) “the persistence of the acquired capability for motor performance”
Motor Memory
Motor program: a memory structure, or representation that stores information necessary for action.
…theories of motor control & learning
Schema theory (Schmidt, 1975,88): we have a motor response schema which provides ‘rules’ governing an action.
Motor Memory
…as a reference of correctness in closed-loop motor control theory:
System goal
Reference mechanism
Executive level
Effector level
Environment
output
input
error
instructions
Decisions
Muscle response
Detection, recognition, matching
Motor Memory
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Carter, 2000
Caudate nucleus: instincts (genetically -coded memories)
Hippocampus: laying down/retrieving (spatial) memories
Putamen: procedural memories
Temporal lobe: LT memories
Amygdala: traumatic, uncon. mems
Human Memory System
• Memories are groups of neurons which fire together in the same pattern each time they become activated (Carter, 2000).
Neurophysiological Basis of Memory
A.
1
2
3
Initial stimulus
Linked connection strong enough to trigger firing
Weak connection
• Memories are groups of neurons which fire together in the same pattern each time they become activated (Carter, 2000).
Neurophysiological Basis of Memory
B.
1
2
3
Initial stimulus
Linked connection strong enough to trigger firing
Weak connection
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• Memories are groups of neurons which fire together in the same pattern each time they become activated (Carter, 2000).
Neurophysiological Basis of Memory
C.
1
2
3
Initial stimulus
Linked connection strong enough to trigger firing
Weak connection
The faster the neural activity, the more likely the charge will pass to neighboring cells
As memory fades, neural connections are lost. (Carter, 2000)
Every perceived sensation creates new neural connections…
But, if not laid down in memory the impression rapidly fades
Lingering patterns connect with and create activity in other neural networks … = an association
In principle, if same neural network is lit up – should give rise to same thought etc. In reality – similar, mutated patterns occur
Neurophysiological Basis of Memory
Magill (2001): verbal and motor memory considered as part of same memory system.
• But two conditions suggest they are not:
• Apraxia – person cannot produce movement from verbal command
• Agnosia – person can produce a movement but cannot name it
• Also, depend on different neural structures
• Verbal: consolidation into LTM depends on medial temporal lobe
Verbal vs. Motor Memory
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Retrieval: the process of calling up information from LT memory (ST memory?)
Retention: the information that we remember
Forgetting: the information we cannot remember Is memory not there?
Cannot retrieve it?
Serial search, activation
Key Definitions…
Measuring Memory
Recognition tests –ability to recognize something from list/group of stimuli.
Recall tests –ability to reproduce something from memory.
How do these relate to our examinations in this class???
Put down your pens…
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83
Tick…..tock
Recall: How many items do you remember from the previous slide?
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Recognition: Which of the following items were on the test slide?
List the 3 proposed stages of information processing ____________________________________________________________________________________________________________
With the condition apraxia, a person: A. Can’t remember the names of movements they do B. Can’t produce movement from a verbal command C. Can’t hear verbal commands D. Can’t remember anything
Stimulus identification Response selection Response programming
Recall vs. Recognition
Two-component Theory of Memory
Declarative Procedural
Episodic Semantic
‘explicit’ ‘implicit’
Short-term Memory
Long-term Memory
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- capacity to retain info for short time (Peterson & Peterson, 1959: <30 sec)
- involves short-term processes - sensation, attention, perception, etc...
- is a workspace for association & integration of new info with retrieved old info.
Short-term Memory
George Miller (1956) - AT&T Laboratories. “The Magic #7” (7 +/- 2 items)
Functional Capacity of Short-term Memory
Immediate recall capacity = 5-9 digits (with or without practice) e.g., phone numbers = 7 digits.
• Chess Players - masters only better than novices with known board patterns
• Joystick movement errors increase after 8
movements (Wilberg & Samela, 1973)
• Dancers - skilled only better than unskilled with
a known sequence (Starkes et al, 1987)
Functional Capacity of Short-term Memory
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C G Q T R L S W D H
E S P N L O L B M W
Remember the following lists:
Functional Capacity of Short-term Memory
Serial Position - movements that are first or last in a series are remembered best
Primary-Recency effect
Factors that Affect STM capacity
Limits to STM can be increased by organizing information - “chunking”
Factors that Affect STM capacity
A chunk is the largest meaningful unit in the presented material that the person recognizes.
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Implications for instruction?
• strategies are important
• present “chunks” of information
• first - last pieces of information remembered best.
Factors that Affect STM capacity
Peterson & Peterson (1959)
00.10.20.30.40.50.60.70.80.91
1 2 3 4 5 6 7
Prob
abili
ty o
f re
call
0 3 6 9 12 15 18 Retention Interval
Duration of working memory: verbal
3 letter patterns, while counting backwards in threes.
Duration of working memory: position
Adams & Dijkstra (1966)
Varied retention interval
???
Criterion position
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Adams & Dijksta (1966)
Motor Memory
Increasing STM through meaningfulness
Semicircular positioning task with 5 or 60 sec retention interval. 3 types of info about criterion mm
Abs
olut
e er
ror (
deg)
9 7 5 0
5 60 Retention Interval (sec)
Clock-face
Verbal label
No label
Shea (1977)
Serial Position Movements that are 1st or last in a series are remembered best
Primary-Recency effect Design:
• Subjects blindfolded • linear positioning task • criterion = total of 3, 6 or 9 movements • recall criterion in same order
Magill & Dowell (1977)
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Abs
olut
e er
ror (
mm
)
!!!!!! 0
1 2 3 4 5 6 7 8 9 Serial Position
200 160 120 80 40
Results
Primacy-Recency effect seen w/longer MMs.
Two-component Theory of Memory
Declarative Procedural
Episodic Semantic
‘explicit’ ‘implicit’
Short-term Memory
Long-term Memory
Long-term memory
LTM is a relatively permanent storage repository for information (Magill, 2001).
Procedural memory:
Enables us to remember how to do something, so that we can perform learned procedures.
This is not verbally accessible.
Implicit
No known capacity
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Represents being able to verbalize what to do (or what we know). Explicit
- Episodic: knowledge of personally experienced events, and their temporal links.
- Semantic: general/conceptual knowledge developed from experience.
Declarative Memory
Early in skill learning: declarative knowledge predominates. As skill develops, you learn to proceduralize declarative knowledge to solve the action problem.
declarative procedural Anderson, 1987
Motor Learning
Forgetting…
Trace Decay: Refers to deterioration of a memory ‘trace’ as a function of time
Anterograde interference: When information presented before the test stimulus causes interference
Retrograde interference: When information presented after the test stimulus causes interference
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Time
Present “useless” info
Present “recall” info
(retention interval)
Recall info
Anterograde Interference
Time !
Present “useless” info
Present “recall” info
(retention interval)
Recall info
Retrograde Interference
Preventing Interference
Transcranial Magnetic Stimulation
(TMS)
Cohen & Robertson (2011) Nature Neuroscience, 14(8): 953-955
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Cohen & Robertson (2011) Nature Neuroscience, 14(8): 953-955
Preventing Interference
Transcranial Magnetic Stimulation
(TMS)
Motor Memory Consolidation
Kantak et al (2010) Nature Neuroscience, 13(8), 923-925
Practice: (arm movement task) Similar movement structure Same time – 800 ms 2 groups: Constant – A3 (120 trials) Variable – A3 (60 trials)
A1, A2, A4 (20 trials each)
Feedback: Target v Actual trajectories RMSE
Randomized!
target actual
Motor Memory Consolidation
Kantak et al (2010) Nature Neuroscience, 13(8), 923-925 Transcranial
Magnetic Stimulation (TMS)
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Motor Memory Consolidation
Kantak et al (2010) Nature Neuroscience, 13(8), 923-925
EoA = End of Acquisition R = RMSE
Interference effects temporally specific to immediate post-practice phase!
Retrograde - memory loss prior to trauma … you forget things you already knew
% o
f nor
mal
m
emor
y
100 50 0
Birth Time of Today Trauma
Time
Amnesia
Anterograde – impairment in the ability to form new memories
% o
f nor
mal
m
emor
y 100 50 0
Birth Time of Today Trauma
Time
Severe - inability to learn anything new Mild - learning is slow and requires more repetition
Amnesia
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Medial Temporal Lobe
Patient H.M Temporal lobe removed
to relieve epileptic seizures.
Profound anterograde amnesia
Medial Temporal Lobe
Anterograde amnesia limited to declarative memories – not procedural (i.e., motor)
Objectives
1. Define / compare and contrast: verbal and motor memory, declarative and procedural memory, short- and long-term memory
2. Describe methods used to assess memory
3. Explain the neurophysiological processes underlying memory
4. Describe different ‘causes’ of forgetting
UNIT 4.1: Role of Memory in Motor Control and Learning
1
Unit 4.2: Attention
Prof John Jeka
Outline:
1. Introduction to attention
2. Theories of Attention
a) Fixed capacity vs. flexible capacity
b) Filter theories
c) Multiple Resource Theories
d) Action Selection
3. Measuring Attention
4. Pre-attention
5. Visual Search
UNIT 4.2: Attention
Objectives
1. To describe / compare and contrast different theories of attention
2. To describe techniques used to assess retention
3. To define pre-attention and to compare and contrast exogenous and endogenous control
4. To define and discuss the components of visual search
UNIT 4.2: Attention
2
What is attention?
In the context of human performance, attention is the conscious or unconscious engagement in perceptual, cognitive, and/or motor activities, before, during, and after performing motor skills
(Magill, 2001)
Is this definition helpful???
Concept 1: humans have a limited availability of resources for performing tasks and gaining information
Capacity to perform task Portion used
to perform task
Traditional resource model (Kroemer et al, 2000)
Concepts in Attention
Concept 2: environmental information must be reduced or filtered
Process Information stream in bits/s Registration in 1,000,000,000 sense organ At nerve junctions 3,000,000
Conscious awareness 16
Lasting impression 0.7
Concepts in Attention
3
Early Theories of Attention
Single, fixed capacity channel
Tasks
Fixed Capacity Models
Driving the car - steering, braking, signaling, etc…
Monitoring position on road
Talking to passengers
Monitoring other cars
The Beginner
Irrelevant info
Fixed Capacity
Driving the car
Monitoring position on road
Talking to passengers
Monitoring road position
Monitoring upcoming stoplight
Deciding to pass
Miscellaneous
The Expert
Fixed Capacity
4
Bottleneck or filter: filters out (ignores) information not selected for further processing.
All information
Selected information
Filter
Filter Theories of Attention
RESPONSE
Selection of Response
Preparation of response
Environmental information
Environmental information
Detection ID
Filter theories differ in terms of where the filtering takes place
Filter? Filter? Filter?
Filter Theories of Attention
Look at this picture for a few seconds…
5
Was the woman using a cellphone?
Was she wearing a necklace?
Was she wearing glasses?
Name of the pub?
Where was your attention?
What was special about the red car?
Color of her jacket?
Filtering occurs at stimulus identification phase
Identified
Broadbent, 1958
Early Theories of Attention
Unidentified?
http://www.youtube.com/watch?v=Ahg6qcgoay4
Do the Test
6
What did you see?
What happened to all the other information … were you never aware that certain objects were
there, or did you filter them at the point that you selected items of
interest?
Broadbent (1958)
Sensory register
Selective filter
Short term memory
S2
S1
Filter Theories of Attention
Triesman (1964) – also assumed filtering to occur early in processing.
However, she believed that the filter had more flexibility, considering it an attenuator, amplifying some stimuli and weakening others.
Filter as Attenuator
7
S1
S2
Sensory register
Short term memory
Attenuator
Triesman (1964)
Filter Theories of Attention
Flexible Capacity Models
• Attention capacity should not be considered fixed as task requirements change.
• Available attention that can be given to a task is a pool of effort. This can be distributed to several activities at once.
• Arousal becomes a factor.
Kahneman, 1973
Miscellaneous determinants
Responses
Arousal Miscellaneous manifestations
of arousal
Enduring disposition
s
Momentary intentions
Evaluations of demands on
capacity
Allocation policy
Possible activities
Available capacity
Flexible Capacity
8
Multiple Resource Theories
• Previous central resource theories consider attention to be taken from a central, single resource.
• Multiple resource theories suggest the presence of many attention mechanisms, each with limited resources, and differing functions.
e.g., Allport (1980), Wickens (1980, 84, 92)
Action-selection Accounts of Attention
• Disputed the very concept of capacity or resource limitations in attention.
• Rather, when we have the momentary goal of an action, the stimuli are all processed in parallel at first. The outcome of this is selection of an action.
• As a result of this selection, certain processes are prevented from happening.
Neuman (1987, 1996)
Change Blindness
http://www.youtube.com/watch?v=vBPG_OBgTWg
Daniel Simonds Experiment:
Derron Brown – Person Swap
http://www.youtube.com/watch?v=38XO7ac9eSs
9
The primary task is the one of interest, and the secondary task is the distractor.
Continuous secondary task:
Assesses if attention is required throughout performance of a motor skill. e.g., motor and verbal skills
Secondary-task probe: Assesses attention demand in preparation, of components of a skill, or at specific moments in performance.
The Dual Task Paradigm
MEASURING ATTENTION
Primary task - move a handle between 2 targets (RH) Secondary task (probe) - press a button in response to a buzzer (LH)
0 45 90 Movement Position of Primary Task (degrees)
Seco
ndar
y Ta
sk R
T
no primary task
Attentional demands change over time
primary + probe
Posner & Keele, 1969
Dual-Task Paradigm
• The process of detecting stimuli in the visual field (usually in the periphery) to guide future attention.
Pre-Attention
10
• The process of detecting stimuli in the visual field (usually in the periphery) to guide future attention.
Can be bottom-up (stimulus driven): if target is sufficiently different from distractors (targets ‘pop-out’). This is exogenous control.
Pre-Attention
Can be top-down (user-driven): uses a limited ‘vocabulary’. Evidence from detection of target colors among heterogenous colors.
This is endogenous control.
Pre-Attention
Pre- Attention to color
Parallel visual search: all items in the display are processed simultaneously-- the search time is independent of the number of distractors
Target = Red Circle
11
Pre- Attention to Form
Parallel visual search: all items in the display are processed simultaneously-- the search time is independent of the number of distractors
Target = Red Circle
Serial visual search: the attention system examines each item, one by one, to determine whether it does or does not have the required conjunction of features
Color and Form
Target = Red Circle
Attention….
• Enhances Detection
• Influences Reaction Time
Behavioral Consequences of Attention
12
Detection
Fixate on central point… fixation
point
attended location
Small circle flashed for 15 msec...
Left
cue ( , or +)
Attention shifts to the right...
Right
Cue / Target +/Right Right/Right Right/Left
% c
orre
ct d
etec
tion
100 80 60 40 20 0
(Posner et al., 1980)
Detection
Cue
Invalid Neutral Valid
300 250 200
Rea
ctio
n Ti
me
(mse
c)
(Posner et al., 1980)
Detection
13
Spotlight Metaphor
Selective attention is… • a "beam" that is moved spatially • may not be divided • enhances detection of events falling within it.
Williams et al, (1999)
How does the anatomy of the retina explain pre-
attention?
Acuity drops to 50% in 2.5 deg of arc.
Spotlight Metaphor
Visual Search - Selective Visual Attention
• Visual search is the process of actively directing visual attention to locate relevant information in the environment.
• Evidence that eye movements directed to a location are preceded by a shift in attention to that area, & the coupling on attention and eye movements is mandatory.
Hoffman, 1998
14
The two visual system:
1. initial detection in the peripheral retina (pre-attention),
2. identification, recognition etc through foveal vision.
Components of visual search
Saccades:
Are conjugate eye movements, responsible for rapid jumping shifts in attention. We have dramatic loss of sensitivity during saccades. Saccades can be anticipatory.
Pursuit tracking eye movements: smooth eye movements which allow us to track slow moving objects of up to 100 deg/sec (decline at 30 deg/sec).
The vestibular-ocular reflex (VOR): stabilizes gaze during head movements.
Fixations: Pauses in visual search, between saccades. They stabilize vision for greater uptake of information. Typically a minimum of 100-120 ms.
Components of visual search
Eye Movements
15
EYE MOVEMENT SUMMARY
http://www.tutis.ca/Senses/L11EyeMovements/L11EyeMovements.swf