Midterm 2

Question 1

Describe the components of the closed-loop control system.

Answer 1

The closed-loop system involves a comparison between the desired state and the actual state, generating an error signal. This signal is processed by the executive system, leading to adjustments by the effector, and feedback updates the actual state.

Question 2

What is the role of efference copy in closed-loop motor control, and what is its main limitation?

Answer 2

Efference copy carries information about the desired state. However, its main limitation is its slow processing speed, as evidenced in studies of online control.

Question 3

What is a reflex?

Answer 3

stereotyped, involuntary, automatic, and typically rapid responses to stimuli.

Question 4

Describe the “loops within loops” concept in movement control.

Answer 4

The M1 and M2 reflexes operate as closed loops within the larger framework of movement control, contributing to dynamic adjustments and feedback integration.

Question 5

How does movement time influence the involvement of M1, M2, and M3 responses?

Answer 5

Shorter movements primarily rely on M1 and M2, while longer movements incorporate M3 responses for more deliberate control.

Question 6

Distinguish between the dorsal and ventral visual streams.

Answer 6

• The dorsal stream specializes in movement control, processing information from the entire visual field for non-conscious guidance of movements.
• The ventral stream handles conscious object identification, primarily in the central visual field.

Question 7

Define optic flow and its significance in movement control.

Answer 7

Optic flow refers to the patterns of light ray movement over the retina, enabling the perception of motion, position, and timing.

crucial for the dorsal stream’s role in guiding movement.

Question 8

Explain the concept of time-to-contact (Tau) in optic flow.

Answer 8

Tau is a measure of time-to-contact derived from optic flow. It’s calculated as the ratio of retinal image size to the rate of change of retinal image size and is proportional to the time remaining before contact with an object.

Question 9

How does the ventral stream contribute to movement control?

Answer 9

The ventral stream provides crucial information about object properties, aiding in movement planning by integrating object knowledge with action goals.

also plays a role in long-latency feedback control.

Question 10

What is a motor program?

Answer 10

A set of motor commands that is prestructured at the executive level and that defines the essentials of a skilled action.

Question 11

What is open loop control?

Answer 11

Centrally determined, prestructured commands that are sent to the effector system and executed without feedback.

Anything operated without feedback.

Question 12

What are degrees of freedom?

Answer 12

• The components of a control system that can vary independently and that are controlled to produce effective action.
• They relate to how many ways a thing can move and how many things can change. For example, a finger has four degrees of freedom

Question 13

How do open loop models function?

Answer 13

• Preplanned instructions specify function, sequence, and timing.
• Once the program starts the system continues to completion without modification.
• There is no ability to detect and correct errors (reflexes).

Question 14

When are open loop models used?

Answer 14

• For rapid, discrete movements.
• In predictable and stable environments.
• To initiate movements.
• Eventually to control long strings of learned/rehearsed movements.

Question 15

How do open loop models initiate movements?

Answer 15

Movements are initiated as open-loop motor programs and progress unchanged if:
1. They are too fast for feedback to register.
2. There is no error and/or no change in the environment.

Question 16

What is the evidence for motor programs?

Answer 16

5 main evidence:
1. Reaction time and movement complexity
2. Deafferentation experiments
3. Central pattern generators (CPGs)
4. Effects of blocking a limb
5. Inhibiting actions (Slater-Hammel expirement)

Question 17

What did Polit & Bizzi (1978) find in their deafferentation experiments?

Answer 17

A monkey’s performance did not significantly deteriorate with deafferentation.

Question 18

What is deafferentation experiments

Answer 18

experiments that show that sensory feedback is not necessary for movement production. This supports the theory that motor programs can be organized and performed in an open-loop framework.

Question 19

What is a central pattern generator (CPG)?

Answer 19

A centrally located control mechanism that produces mainly genetically defined, repetitive actions such as locomotion or chewing. For example, a single simple input can result in a complex, repetitive behavior. CPGs are similar to a motor program, but they refer to inherited rather than learned skills.

Question 20

What did the limb blocking experiemnt reveal?

Answer 20

Even when a limb was blocked during the experiment, the participant started to brake the movement. This suggests that aspects of the program cannot be stopped even if they are useless (or detrimental).

Question 21

What is the Slater-Hammel experiment?

Answer 21

This experiment investigated how late an experimenter could stop a participant’s hand and the participant could still successfully stop their response. It sought to determine the “point of no return” for executing a program or when a person can inhibit an action

Question 22

What is the relationship between reaction time and movemnt complexity?

Answer 22

The more complex a movement, the longer the preparation time, resulting in longer reaction times. For example, it will take longer to react and complete a more complex movement sequence involving more limbs.

Question 23

What are the effects of blocking a limb?

Answer 23

the first 100 ms of a movement is preprogrammed and cannot be influenced.

Question 24

What are examples of motor programs?

Answer 24

1. Postural (anticipatory) adjustments
2. Flexible reflexes

Question 25

What is the reflex-reversal phenomenon?

Answer 25

A special case of reflex activity involving different responses to the same stimulus.

Question 26

What does a motor program need to do?

Answer 26

1. Define and issue commands to the muscles needed to produce (initiate) the goal movement.
2. Coordinate the many degrees of freedom needed to produce an effective and efficient action (e.g. force, timing, sequencing, duration).
3. Specify and initiate any preliminary postural adjustments needed to support the upcoming action.
4. Modulate reflex pathways.

Question 27

What are the challenges to motor program theory?

Answer 27

1. It is very difficult to define, issue commands, coordinate degrees of freedom, specify and initiate postural adjustments, and modulate reflex pathways
2. The storage problem
3. The novelty problem

Question 28

What is the storage problem in motor program theory?

Answer 28

We would need infinite memory to store programs for controlling the infinite number of movements people can produce.

Question 29

What is the novelty problem in motor program?

Answer 29

How do you create a motor program for a movement that you have never produced before?

Question 30

What are generalized motor programs?

Answer 30

A motor program that defines a pattern of movement rather than a specific movement. They can change parameters to produce movement variations that meet different environmental demands.

Question 31

What are the parameters of a generalized motor program?

Answer 31

The variable inputs to a generalized motor program which result in different movements. For example, in a tennis stroke, some features remain the same from shot to shot (invariant features) and some are changed each time (surface features). When we change parameters, we change surface features.

Question 32

What is an invariant feature?

Answer 32

the fundamental characteristics of a movement that remain constant even when surface features (parameters) are modified.

the defining elements of a movement pattern.

Question 33

What is the generalized motor program theory?

Answer 33

This theory uses the analogy of a mathematical function (e.g., the function of a line): Y = mx+b. “m” and “b” are parameters. For any “m” and any “b” you will ALWAYS get a line (invariant feature), but its slope (m) and intercept (b) will change (surface features).

Question 34

What are the stages of information processing according to the generalized motor program theory?

Answer 34

1. Stimulus identification (Perception): Sensory stimulation is received and perceived.
2. Response selection (Decision): A decision is made about how to respond to the stimulus.
3. Response programming (Action): The motor program is selected and parameterized. This includes:
   ○ Selecting a GMP (e.g., throw vs. kick) and retrieving it from long-term memory.
   ○ Parameterizing the GMP.

Question 35

What is relative timing?

Answer 35

A measure of the temporal structure of a movement, in which the ratios among the durations of various movement features are used to define the temporal pattern (fundamental timing structure). The percent of total movement time spent in each part of the task is the same regardless of total movement time.

Question 36

What is the evidence for relative timing?

Answer 36

Movement ratios remain the same even when these parameters change:
● Speed of rapid movement
● Size of action
● The limb used
● Force used to produce the action
● Trajectory of movement

Question 37

What are classes of movements?

Answer 37

A group of movements that share the same relative timing “fingerprint” For example:
● Throwing: Can vary throw distance (with parameters like force), but once the capability is exceeded, switch to a different motion (heave)
● Walking: Can walk on a treadmill at a variety of speeds while keeping a consistent gait. But, at some speed, you must switch to running

Question 38

What are the parameters in generalized motor programs?

Answer 38

● Movement time: The overall duration of the movement, which can be adjusted to be slower or faster.
● Movement amplitude: The size of the movement, such as the distance a limb travels, can be modified to be larger or smaller.
● Effector: The body part or limb used to perform the movement, can be changed.

Question 39

What is fundamental timing structure?

Answer 39

The sequencing and timing of a movement that define the underlying pattern.

Question 40

What is the stereo system analogy of generalized motor programs?

Answer 40

● A generalized motor program is like a function that accepts different parameters (y = mx + b).
● Different parameters result in different movements (with different surface features) that are based on the same underlying program.
● With practice, you improve your ability to select (and variety of) appropriate parameters for a given context.

Question 41

What is the fundamental principle of the speed-accuracy trade-off?

Answer 41

If you perform the same action more quickly, it will be done with less accuracy.

Question 42

What does Fitts’ Law tell us about movement time?

Answer 42

Large amplitude movements to wide targets take the same time as small amplitude movements to narrow targets.

Question 43

What is the significance of the linear relationship between movement time and the index of difficulty in Fitts’ Law?

Answer 43

The linear relationship means that for every unit increase in the index of difficulty, there is a proportional increase in movement time. This relationship has been observed across various conditions (e.g., underwater, in space), populations (e.g., children, adults), and body parts (e.g., fingers, hands, arms), indicating a general law of motor behavior.

Question 44

What is an example of how Fitts’ Law is applied to everyday design?

Answer 44

Keyboard designers make frequently used keys larger and closer together to reduce the index of difficulty and allow for faster typing speeds. This is just one example of how Fitts’ Law is considered in user interface and device design.

Question 45

What is the linear speed-accuracy trade-off?

Answer 45

This describes the relationship between speed and accuracy for rapid, discrete, open-loop movements where there is no time for feedback. It states that as movement time decreases, effective target width (We) increases, leading to reduced accuracy.

Question 46

What are the two main effects observed in the linear speed-accuracy trade-off for rapid movements?

Answer 46

1. For a given rapid movement time, as amplitude increases, effective target width increases.
2. As movement time decreases, effective target width increases. These effects highlight that faster movements generally come at the cost of reduced spatial accuracy.

Question 47

What does the linear speed-accuracy trade-off suggest about motor programs?

Answer 47

Both open-loop (very rapid) and closed-loop (slower) control mechanisms demonstrate a speed-accuracy trade-off, indicating a fundamental constraint in motor control.

Question 48

What are the sources of error in very rapid movements?

Answer 48

The main source is noise within the nervous system, particularly at the level of the spinal cord. Each synapse introduces variability (noise) due to factors like the number of receptors and neurotransmitters. This noise accumulates as signals travel through the nervous system, especially during rapid movements

Question 49

How does force contribute to error in rapid movements?

Answer 49

As force production increases (up to about 70% of maximum), variability in muscle responses also increases, introducing more noise into the system.

Question 50

How does the relationship between force and variability explain the open-loop speed-accuracy trade-off?

Answer 50

In rapid movements, higher force leads to greater variability in muscle responses, resulting in less precise control over the movement’s endpoint and therefore reduced spatial accuracy.

Question 51

What is an exception to the speed-accuracy trade-off?

Answer 51

Movements performed at or above approximately 70% of maximum force become less variable, leading to increased accuracy.

Question 52

What is the difference between spatial accuracy and timing accuracy?

Answer 52

● Spatial accuracy: The precision of the movement’s endpoint in space.
● Timing accuracy: The precision with which a movement is executed at a specific time.

Question 53

How does movement speed affect timing accuracy?

Answer 53

Timing accuracy improves with faster movements, unlike spatial accuracy which generally decreases with speed.

Question 54

What is fundamental timing structure?

Answer 54

The sequencing and timing of a movement that define the underlying pattern

Question 55

What is the stereo system analogy of generalized motor programs?

Answer 55

• A generalized motor program is like a function that accepts different parameters (y = mx + b). [14]
• Different parameters result in different movements (with different surface features) that are based on the same underlying program. [14]
• With practice, you improve your ability to select (and variety of) appropriate parameters for a given context.

Question 56

What is Fitts’ Law?

Answer 56

• Fitts’ Law states that movement time (MT) is proportional to the index of difficulty (ID), which is calculated as Log2(2A/W), where A is the distance to the target and W is the width of the target.
• This means that MT increases as ID increases, indicating that tasks with smaller targets or greater distances require more time to complete.

Question 57

Explain Schmidt’s Law and its relation to the speed-accuracy tradeoff

Answer 57

• Schmidt’s Law describes the linear speed-accuracy tradeoff, stating that effective target width (We) is proportional to movement amplitude (A) divided by movement time (MT), or We ~ A/MT.
• This implies that for rapid movements, error increases with shorter MT and larger A.
• In simpler terms, faster movements are generally less accurate, and movements over larger distances tend to be less accurate.

Question 58

What are the sources of error in rapid movements?

Answer 58

Errors in rapid movements can stem from:
○ Synapse activity
○ Muscle recruitment
○ Muscle coordination affecting resultant force

Question 59

Are there exceptions to the speed-accuracy tradeoff?

Answer 59

Yes, exceptions to the speed-accuracy tradeoff include:
○ Tasks involving maximum force
○ Tasks focused on timing accuracy
■For example, a batter in baseball prioritizes timing accuracy over spatial accuracy, unlike a golfer putting.

Question 60

What is a bimanual skill, and provide common examples.

Answer 60

A bimanual skill is a skill that requires the control and coordination of both hands. Examples include:
○ Playing the piano
○ Typing

Question 61

Describe the Bimanual Fitts Task

Answer 61

The Bimanual Fitts Task involves performing Fitts’ tasks with both hands simultaneously, manipulating the ID (distance/width ratio) for each hand.

Question 62

What are the expected results of a bimanual fitts task

Answer 62

Expected Results: Based on unimanual Fitts’ Law, it was predicted that each hand would perform independently, with MT corresponding to the individual ID of each hand.

Question 63

What are the actual results of a binmanual fitts task

Answer 63

Actual Results: The movement of the right limb was influenced by the task demands of the left limb, regardless of the right limb’s ID. This suggests that the two limbs are coordinated, potentially by a shared motor command or program.

Question 64

Explain the Bimanual Obstacle Avoidance Task and what it suggests.

Answer 64

• The Bimanual Obstacle Avoidance Task requires participants to move both hands simultaneously, with one hand needing to avoid an obstacle.
  ○ The results showed that the movement of the right hand was affected by the obstacle avoidance task of the left hand, even when the right hand did not have to avoid the obstacle.
  ○ This provides further evidence for a single or coordinated motor plan governing both limbs.

Question 65

Explain the Gamma-V experiment and its implications.

Answer 65

The Gamma-V experiment involves asking participants to draw a capital V with one hand and the Greek letter gamma (Γ) with the other hand simultaneously.
○ Unimanual Results: Individuals can successfully form separate motor programs for each shape when performed independently.
○ Bimanual Results: Performing both tasks simultaneously leads to significant interference, indicating difficulty running two motor programs concurrently. This supports the concept of a single motor program limitation

Question 66

Describe the observations and research findings on continuous timing in bimanual coordination.

Answer 66

○ In-phase movements, where both limbs move in the same direction at the same time, are more stable than out-of-phase movements.
○ Anti-phase movements, where limbs move in opposite directions, are also relatively stable but less so than in-phase movements.
○ Out-of-phase movements, where limbs move with no clear timing relationship, are the least stable.

Question 67

How does the concept of coordination stability relate to the speed-accuracy tradeoff?

Answer 67

Coordination stability suggests a strategy for managing the speed-accuracy tradeoff:
○ As speed demands increase and a particular coordinated movement (e.g., anti-phase) becomes unstable, the motor system can switch to a more stable pattern (e.g., in-phase).
○ This is similar to switching from walking to running on a treadmill when walking becomes unstable at higher speeds.

Question 68

What does research by Cisek & Kalaska suggest about parallel motor planning?

Answer 68

○ Cisek & Kalaska’s research on affordance competition suggests that the brain can create multiple motor plans simultaneously.
○ Recordings from the dorsal premotor (PMd) cortex, associated with reach direction, showed activity representing more than one potential reach target.
○ However, only one motor plan is typically executed, suggesting competition between plans that is resolved before or during movement.

Question 69

Do the findings on parallel motor planning contradict the idea of a single motor program?

Answer 69

While the research by Cisek & Kalaska supports the existence of multiple motor plans, it doesn’t necessarily contradict the single motor program concept for multi-limb movements.
○ Multi-limb coordination likely requires motor programs with shared properties, such as timing structures, which could impose limitations on the number of programs executed concurrently.

Question 70

What are the three key takeaways regarding speed accuracy and coordination?

Answer 70

1. Fitts’ Law: Movement time increases as the index of difficulty (target distance/width ratio) increases.
2. Linear Speed-Accuracy Tradeoff: Error increases with shorter movement time and larger movement amplitude in rapid movements.
3. Coordination Stability: When speed demands destabilize one coordinated movement pattern, the motor system can switch to a more stable pattern.

Question 71

Why do scientists study individual differences?

Answer 71

To:
○ Understand abilities: Expertise involves more than just practice. Fundamental characteristics, largely inherited and unaffected by practice, may underlie specific skills.
○ Make predictions: By using criteria unique to an individual, we can predict their likelihood of success or failure in a given situation. This has applications in areas like insurance.

Question 72

What are the characteristics of individual differences?

Answer 72

Individual differences:
○ Are stable across multiple attempts of the same skill
○ Persist over time
○ Are difficult to determine from a single measurement

Question 73

Provide examples of factors influencing individual differences

Answer 73

Motor abilities, attitutes, body type, cultural background, emotional makeuo, previous movement experience etc.

Question 74

What is the experimental method of studying motor behaviour

Answer 74

■ Focuses on examining the effects of specific variables on motor behavior in general.
■ Treats individual differences as a source of error (noise).
■ Typically compares the means of one test variable between two or more subject groups.
■ Aims to establish cause-and-effect relationships in human behavior.

Question 75

What is the differential method of studying motor behaviour

Answer 75

■ Focuses on examining the differences between and among individuals on measures of motor behavior.
■ Considers these differences as the primary focus of study rather than noise.
■ Involves comparing individual performance on one test to their performance on another test within a single group.
■ Employs correlation techniques to analyze relationships between variables.
■ Does not establish causation.

Question 76

What is correlation, and how is it visualized?

Answer 76

○ Correlation is a statistical measure that quantifies the strength and direction of the relationship between two or more variables.
○ It is typically visualized using a scatter plot, where each data point represents an individual’s scores on two measures.
○ A “best fit” line is drawn through the data points to represent the overall trend.

Question 77

Explain how the strength of a correlation are determined from a scatter plot.

Answer 77

The closer the data points cluster around the best fit line, the stronger the correlation between the variables. A stronger correlation suggests a more consistent relationship between the variables.

Question 78

Explain how the direction of a correlation are determined from a scatter plot.

Answer 78

The slope of the best fit line indicates the direction of the relationship:
■ A positive slope (upward trend) indicates a positive correlation, meaning that as one variable increases, the other tends to increase as well.
■ A negative slope (downward trend) indicates a negative correlation, meaning that as one variable increases, the other tends to decrease.

Question 79

Describe the correlation coefficient (r) and its properties.

Answer 79

○ The correlation coefficient, denoted by ‘r,’ quantifies the strength and direction of the relationship between variables.
○ r ranges from -1 to +1:
■ |r| = 1 represents a perfect correlation, where all data points fall precisely on the best fit line.
■ |r| = 0 indicates no correlation, suggesting no relationship between the variables.
○ The sign of ‘r’ (+ or -) indicates the direction of the correlation (positive or negative).
○ The magnitude of ‘r’ represents the strength of the correlation: a larger magnitude indicates a stronger relationship.

Question 80

What is r², and how is it interpreted?

Answer 80

○ r² (r-squared) is the coefficient of determination, calculated by squaring the correlation coefficient (r).
○ It represents % that two groups have in common (correlated)

Question 81

Distinguish between ability and skill.

Answer 81

○ Ability: A stable, enduring trait primarily determined by genetics, underlying skilled behavior and largely unaffected by practice. Represents the inherent potential for a skill.
○ Skill: A capability developed through practice, representing proficiency in performing a specific task. Demonstrates the learned and refined execution of an ability.

Question 82

How do abilities and skills interact to influence performance?

Answer 82

○ Abilities set the limits on an individual’s potential for skill development and performance.
○ Skills can be developed and refined within the boundaries set by one’s abilities.
○ Individuals with the same abilities may develop different skills based on practice and experience.

Question 83

Explain the General Motor Ability theory.

Answer 83

Proposed by McCloy and Brace in the 1920s-30s
○ Suggests that a single, inherited motor ability is responsible for all skill performance.
○ Implies that individuals gifted in one motor skill will excel in all others.
○ Parallels the concept of general mental ability (IQ).
○ largely discredited by research findings.

Question 84

Describe the Specificity Hypothesis.

Answer 84

○ Proposed by Henry in the 1960s
○ Asserts that numerous specific, independent motor abilities underlie motor performance.
○ Posits that each task requires a unique combination of abilities.
○ Implies that abilities needed for one task are largely distinct from those needed for another.

Question 85

Outline Fleishman’s theory of Groupings of Abilities.

Answer 85

Proposes that while abilities are independent, the number of abilities crucial for any task is smaller than suggested by the Specificity Hypothesis.
○ Acknowledges that different tasks may share some common underlying abilities.
○ Represents a middle ground between General Motor Ability and Specificity Hypothesis.

Question 86

How are correlation studies used to test different theories of motor abilities?

Answer 86

○ Researchers examine correlations between performances on different motor tasks.
○ The General Motor Ability theory predicts a strong correlation (r ≈ 1) between all motor tasks.
○ The Specificity Hypothesis anticipates very weak or no correlation (r ≈ 0) between most tasks.
○ Groupings of Abilities predicts moderate correlations (0.2 < r < 0.8) between tasks sharing common abilities.

Question 87

What have correlation studies revealed about the validity of the General Motor Ability theory?

Answer 87

○ Correlation studies have consistently found moderate correlations between different motor tasks, even among the most highly related ones.
○ These findings refute the General Motor Ability theory, indicating that a single general motor ability does not account for performance across all motor skills.

Question 88

4 things you need in data analysis to draw conclusions

Answer 88

1. Distribution (normal or not)
2. Central tendency (mean)
3. Variability (standard deviation)
4. sanmple size

Question 89

What are the main theories of motor abilities?

Answer 89

General motor ability, specificity hypothesis, groupings of abilities

Question 90

How do abilities contribute to the development of skills?

Answer 90

○ Any given skill is influenced by a limited set of abilities.
○ Abilities have varying levels of importance for different skills.
○ Each skill has a unique combination of contributing abilities.
○ Skills can share some common underlying abilities.

Question 91

What is factor analysis, and how is it used in understanding abilities?

Answer 91

○ Factor analysis is a statistical technique used to identify the underlying factors, or abilities, that contribute to performance on various tasks. It looks for patterns in the correlations between different tests to group related abilities.
○ Researchers can use factor analysis to identify specific abilities relevant to a particular skill. This information can then be used for talent identification and training program design.

Question 92

Why is predicting future skill capability based on current ability challenging?

Answer 92

○ Growth and Development: Abilities change as individuals grow and mature, making it difficult to predict long-term skill development.
○ The Problem of Practice: The pattern of abilities that underlie a skill changes with practice and experience. Abilities that are important for novice performance may become less critical as expertise develops.
○ Difficulty in Measuring Abilities: Accurately assessing abilities, as opposed to skills, is inherently challenging.

Question 93

What is the “relative age effect,” and how does it illustrate the challenges of prediction?

Answer 93

○ The relative age effect describes a bias where individuals born earlier in a selection year (e.g., January vs. December for school or sports) have an advantage due to their relative maturity and development.
○ In sports, this can lead to early selection and more opportunities for athletes born earlier in the year, potentially creating a self-fulfilling prophecy.
○ While the relative age effect can be strong, it is not absolute, and other factors like motivation, access to training, and the development of specific skills play a crucial role in determining long-term success.