Chapters 7 & 8

Question 1

What is Fitts Law?

Answer 1

• For skills in which accuracy is a task objective, Fitts’ Law describes the relationship between speed and accuracy based on two key parameters

Question 2

What are the two key parameters for Fitts Law?

Answer 2

1. the distance to the target (which is equivalent to the movement amplitude)
2. the size of the target.

In simple terms, Fitts’ Law states that, for motor skills requiring accuracy, when speed is maximized, accuracy is reduced and vice versa.

For this reason, the relationship quantified by Fitts’ Law is commonly known as the speed-accuracy trade-off.

Question 3

In practical terms, Fitts Law means?

Answer 3

this means that the faster we move the more difficult it is to be accurate, or (said in a slightly different way), the more accurate we want to be the more difficult it is to move quickly.

Question 4

Fitts’ Law is a mathematical relationship which describes?

Answer 4

the speed-accuracy trade-off in terms of the distance moved and the target size

Question 5

Fitts’ Law states that if target size decreases, then?

Answer 5

movement speed will have to decrease to maintain the same level of accuracy.

Question 6

Fitts’ Law states that if the distance increases, then?

Answer 6

movement speed will also decrease to maintain the same level of accuracy.

Question 7

Fitts’ Law can be used to quantify?

Answer 7

quantify an index of difficulty (ID) for various aiming skills.

Question 8

o Fitts’ Law states that as you increase the index of difficulty, then?

Answer 8

the movement time will have to increase (i.e., movement speed decreases) if you want to maintain the same level of accuracy.

Question 9

What is the Index of difficulty (ID)?

Answer 9

Fitts’ Law can be used to quantify the level of difficulty of different skills based on the target width and the distance from the starting point to the target. (ID number becomes higher with difficulty)

Question 10

What is synchronous?

Answer 10

When the limbs move together so that each limb does the same thing (i.e., has the same coordination pattern).

• the same motor commands are sent out by the motor cortex in the brain to both limbs

Question 11

What is asynchronous?

Answer 11

When the limbs move separately so that each limb does a different thing (i.e., each limb has a different coordination pattern)

• the brain has to send different sets of commands to the right and left sides of the body

Question 12

What are Bimanual Coordination Skills?

Answer 12

When motor skills are performed that involve the use of both arms.

• Depending on the skill, the bimanual arm movements may occur synchronously or asynchronously.

Question 13

What is Bimanual coordination?

Answer 13

refers to motor skills that require the simultaneous use of both arms.

o Bimanual coordination skills require the two arms to move with either the same or different spatial and/or temporal (i.e., timing) characteristics.

Question 14

The CNS has a preference for performing?

Answer 14

synchronous arm movements (i.e., synchronous arm movements are much easier to perform; asynchronous arm movements require substantially more learning).

Question 15

To perform asynchronous tasks the CNS has to?

Answer 15

the CNS has to override its preference to perform the movements synchronously and reorganize the motor commands sent to both limbs (i.e., the CNS has to learn a new coordination pattern).

Question 16

Why are Asynchronous tasks considerably more difficult to perform? What are polyrythms?

Answer 16

Skills that require maintaining multiple, simultaneous rhythms, called polyrhythms, are very difficult to perform. Examples include drumming and playing the piano.

Question 17

What is a continuous skill?

Answer 17

Many activities that humans perform are cyclical; i.e., they repeat over and over in a specific pattern. Some of these activities include walking, running, swimming and cycling.

Question 18

What is Arm-leg Opposition?

Answer 18

If you pay close attention to how your limbs move when you walk, you’ll notice that both arms swing gently back and forth in a rhythmic fashion, apparently of their own accord, and that your right arm will swing forward as your left leg steps to make contact with the ground (same when we run).

Question 19

What are Central Pattern Generators (CPGs)?

Answer 19

spinal circuits which are activated when the spinal cord receives sensory information from the mechanoreceptors in the bottom of our feet, in our joints and in our muscles and tendons

• detect changes in the position and motion of our limbs, which activates the CPG and generates the sensation called proprioception
• Once the proprioceptive switch that activates the spinal circuit has been turned on, the circuit sends alternating electrical impulses to the muscles of all four limbs, so that they move in a coordinated rhythmic fashion.

Question 20

Understanding the neural control mechanisms of walking has important implications for who and why?

Answer 20

rehabilitation of patients with spinal cord injury because, in many cases, the central pattern-generating circuits are not damaged by the injury.

Question 21

The rhythmic coordination pattern for walking consists of?

Answer 21

an arm/leg opposition pattern (one arm swings forward while the opposite leg swings forward to take a step).

Question 22

Studies on deafferented animals (animals that have received a spinal cord injury so that no sensory information can reach the brain) have shown?

Answer 22

that rhythmic muscle activity (e.g., walking) still occurs even when sensory input cannot get to the brain. This demonstrates that the basic coordination pattern of walking is regulated by CPGs in the spinal cord (and that the basic movement pattern is not controlled by the brain).

Question 23

Summarize Fitts Law

Answer 23

Fitts' Law
↑ speed, ↓ accuracy
↑ accuracy, ↓ speed
↓ target size, ↓ movement speed
↑ distance, ↓ movement speed
↑ index of difficulty, ↑ movement time

Question 24

What is Bimanual Coordination?

Answer 24

• The brain has a preference for performing synchronous arm movements
• Skills that involve asynchronous movements are considerably more difficult to perform than skills that involve synchronous movements

Question 25

What are Gait Patterns?

Adapting and/or monitoring the basic pattern of gait requires?

Answer 25

• CPGs in the spinal cord produce the basic rhythmic coordination pattern of walking
• Adapting and/or monitoring the basic pattern of gait requires cerebral control

Question 26

What does it mean to Initiate Movement?

Answer 26

The central idea of this chapter is that the CNS plans and prepares movements in advance, and that the planning and preparation processes take time.

• Consequently, movements take time to prepare, and the amount of time needed for movement preparation depends on a variety of factors that relate to the task and/or the situation as well as the individual performing the movement.

Question 27

What is one of the most important things the brain needs to do when initiating movement?

Answer 27

• One of the most important things the brain needs to do to plan movements in advance, is to process information (sensory feedback) so it can make decisions about how best to respond to the situation at hand.
• Because movements take time to prepare, quantifying the amount of time it takes to react to different environmental stimuli can help provide an understanding of how the brain processes information for the purpose of movement planning.

Question 28

What is the key point about how reaction time is an important parameter related to action preparation?

Answer 28

Movement (action) preparation.

Question 29

What is Movement (action) preparation?

Answer 29

refers to the specific preparation the CNS makes prior to initiating a movement (recall that the term action is synonymous with movement).

o Recall that RT is defined as the time interval between the presentation of a stimulus (e.g., a yellow traffic light) and the initiation of the movement (e.g., moving your foot to press on the brake pedal).

o RT can be used as an index of movement preparation (i.e., it quantifies how long movements take to prepare).

Question 30

o In relation to action preparation, the more information the CNS has to process, the…?

Answer 30

the longer it will take to initiate the movement (because the planning and preparation processes take longer).

Question 31

The preparation of movement depends on many factors, which can be organized into three different categories. They are?

Answer 31

1. Task/Situation Characteristics
2. Performer Characteristics
3. CNS Responsibilities

Question 32

What are Task/Situation Characteristics?

Answer 32

those factors related to the task and/or the situation that influence movement preparation.

Question 33

What are the subdivisions of Task/Situation Characteristics?

Answer 33

1) Increase in information
2) Predictability
3) Stimulus-Response Compatibility
4) Foreperiod
5) Movement Complexity
6) Movement Accuracy
7) Movement Repetitions

Question 34

What does it mean to increase in information?

Answer 34

Based on studies that have used RT as an index of movement preparation, it has been shown that movements in which a greater number of decisions have to be made take longer to prepare. (Hick’s Law)

Question 35

Hick’s Law states that?

Answer 35

 RT increases as the number of response choices (or alternatives) increases.

 Hick’s Law can be expressed mathematically (and therefore predicted), so that RT increases logarithmically with the number of stimulus-response alternatives.

 Hick’s Law relates the increase in RT to the amount of information processed by the brain (i.e., the # of bits of information). The more information (the greater the # of bits) that has to be processed, the longer it will take to plan and prepare the movement, and therefore, the slower the response (i.e., the longer it takes to initiate the movement).

Question 36

What is predictability?

Answer 36

Research shows that as the predictability of a stimulus increases, the reaction time will decrease.

• this means that if you can guess what is going to happen, your brain can prepare what to do in advance (i.e. before the stimulus is presented), and as a result your reaction time will be faster.
• When you bias your responses this way, you’re taking advantage of what is known as the cost-benefit trade-off.

Question 37

What is Cost-benefit trade-off?

Answer 37

biasing your movement response to decrease your RT based on prior knowledge of the task situation.

• e.g., when playing basketball against a familiar opponent, you might guess that the opponent will fake right and then go left, since you have learned from experience that this is the opponent’s preference. The cost is having the opponent beat you and take a shot if you guess incorrectly, but the risk is worth it if the probability of this occurring is quite low. The benefit occurs when you guess correctly, and are able to stop the opponent because you were prepared in advance and reacted very quickly.

Question 38

What is Stimulus-Response Compatibility?

Answer 38

This aspect of movement preparation relates the compatibility of a movement response to the stimulus that caused it.

• I.e. the steering wheel of a car. If you turn the wheel counter-clockwise (your hands move to the left), the car will go left, and vice versa.
• The important point here is that the brain can react more quickly when the response is compatible with the stimulus.

Question 39

What is Stimulus-Response Incompatibility?

Answer 39

i.e Turning the steering wheel in a car clockwise to go left, or pushing the yoke in a plane down to go up

• When the response is incompatible, you’ll find that you take longer to react because your brain needs time to flip everything around and figure out what the correct response is.
• So, as movement responses become more compatible with the stimulus, RT will decrease.

Question 40

What is the foreperiod?

Answer 40

the time between a warning signal (for e.g., a starter in a race saying “Take your marks”) and the presentation of a stimulus (e.g., the gun going off).

• RT is faster for situations in which a warning signal occurs (i.e., a foreperiod is present).
• The brain can use the foreperiod to start preparing the movement before the stimulus occurs.

Question 41

Research shows that two important factors influence the degree to which a foreperiod can have a positive effect on RT, which are?

Answer 41

o There is an optimal length of time for the foreperiod to occur to benefit RT. If the foreperiod is too long or too short (i.e., < 1 sec. or > than 4 secs.), it will have a minimal impact on RT.

o RT will decrease as the regularity of the foreperiod increases (this improves anticipation, so that the action can be prepared in advance). This is similar to point #2 concerning predictability, in that the more consistent the foreperiod becomes, the more predictable the presentation of the stimulus is.

Question 42

What is movement complexity?

Answer 42

RT increases as movement complexity increases. Movement complexity refers to the number of component parts of a movement. The more complex the skill, the more movement components it contains, and the longer it takes to prepare. (e. guitar chords)

• RT increases as the complexity of the action increases.
• More complex skills contain an increased number of movement components.

Question 43

What is movement accuracy?

Answer 43

as the accuracy demands of the task increase, so does the RT (i.e., the time for movement preparation).

• Fitts’ Law demonstrates that an inverse relationship exists between movement accuracy and speed, and this is a similar relationship;
• i.e., the greater the accuracy requirements of the skill, the more preparation needed by the CNS, which means a slower RT.

Question 44

What is movement repetition?

Answer 44

RT decreases as the number of movement repetitions increases. This means that as you continuously repeat a movement over and over, there is less preparation required by the CNS, because the preparation from the previous repetition can be held in working memory and accessed very quickly to perform the next repetition.

Question 45

What is Psychological Refractory Period (PRP)?

Answer 45

This refers to a special case of movement preparation in which the RT for a 2nd stimulus is delayed because the CNS is still busy responding to the 1st stimulus.

Question 46

What happens during the Psychological Refractory Period (PRP)?

Answer 46

• What happens is that when a stimulus is presented immediately after another, the brain needs time (after initiating the 1st response) to plan and prepare the 2nd response.
• The brain cannot plan the 2nd response until it has finished initiating the 1st response.
• This creates a slight delay in responding to the 2nd stimulus.
• For example, this is the reason why head fakes work, because your opponent will be busy responding to the 1st stimulus (the fake) while you are initiating the 2nd stimulus (the move in the opposite direction which they will not be able to respond to).

Question 47

What are performance characteristics?

Answer 47

look at those factors related to the characteristics of the performer (i.e., individual characteristics) that influence the amount of time needed to plan and prepare movements.

Question 48

What are the subdivisions of performance characteristics?

Answer 48

Alertness
Attentional Focus
Practice

Question 49

What is alertness?

Answer 49

refers to whether an individual is ready (prepared) to respond to a stimulus (i.e., alertness refers to the individual’s state of readiness). If you expect that a stimulus is about to occur, then you will be ready to respond.

Question 50

What happens if you do not have alertness?

Answer 50

• If not, you may be surprised and not prepared to move.
• the presence of a warning signal will alert the individual that a stimulus is about to occur and the foreperiod will be used to prepare the movement.
• In this case, RT will be optimal when the foreperiod is optimal
• In situations where the foreperiod is too long, RT will increase because the brain will lose focus and occupy itself by attending to other thoughts or tasks (daydreaming for example).

Question 51

What are vigilance tasks?

Answer 51

are tasks that demand long-term alertness (e.g., an outfielder, goalie, security guard). In situations where nothing happens for long periods of time (for e.g., being a goalie on a team with a very good offense), it can be difficult to react quickly because of the potential for the level of alertness to drop.

Question 52

What is the relationship between RT and alertness?

Answer 52

The presence of a foreperiod will decrease the RT due to an increased level of alertness. RT will be suboptimal if the foreperiod is too long or too short (optimal = approx. 1– 4 seconds)

Question 53

What is attentional Focus?

Answer 53

how an individual’s attention is directed. The subject of attention is quite extensive and important for movement.

• Specifically, RT (and therefore your movement preparation) is affected by how you choose to direct your attention.

Question 54

Research shows that directing your attention to focus on the sensory stimuli received from the environment results in faster reaction times than focusing on the movement response. What does this mean?

Answer 54

o This means that it is better to have what is called a sensory set (sensory focus) than a motor set (movement focus)

o For example, if you want to react quickly to a starter’s pistol, it is better to focus on the sound of the gun than to focus on how hard you’re going to push against the block as soon as the gun goes off.

Question 55

What is practice?

Answer 55

how much an individual practices also has a significant effect on movement preparation. Increasing the amount of practice (i.e., an individual’s familiarity and experience with the movement situation) will decrease the amount of time it takes to respond to a stimulus (decreases RT).

Question 56

Movement automaticity increase with?

Answer 56

movement automaticity increases with practice (i.e., movement responses become very automatic).

Question 57

Practice also reduces the increase in?

Answer 57

Practice also reduces the increase in RT due to stimulus-response incompatibility, and is important for the development and refinement of motor programs

Question 58

What are CNS Responsibilities?

Answer 58

Every time your brain decides it’s going to move, it will engage in several different processes and functions to ensure that the movement it selects will be accurate (i.e., appropriate) and efficient.

Question 59

What are the subdivisions for CNS Responsibilities?

Answer 59

1) Perceptual/Cognitive Processing
2) Postural Preparation
3) Limb Movement
4) Object Control Parameters
5) Spatial Coding
6) Rhythmicity

Question 60

What is Perceptual/Cognitive Processing?

Answer 60

1) Perceptual/Cognitive Processing- For movements to be appropriate, the brain must extract meaning from (i.e., perceive) the sensory information it receives from the visual and somatosensory cortices.

• The brain must process this information and then use it to select and initiate the correct response.
• in all movement situations, the brain will engage in perceptual/cognitive processing which it will use to make decisions to select the correct movement response.
• Ex. child crossing the road.

Question 61

What is Postural Preparation?

Answer 61

Prior to initiating limb movement, the brain will activate the body’s postural control muscles to ensure that the body is stable and will not be put off balance by the movements it is about to perform.

• Without this postural “feedforward control” mechanism, you would literally fall over every time you bent over to pick something up off the ground.
• With respect to movement planning and preparation, postural control precedes limb movement initiation.

Question 62

What is Limb Movement?

Answer 62

For limb movements to be successful, the brain must select (as part of the preparatory process) the specific movement parameters that are needed for any given situation.

• This includes planning the appropriate movement trajectory, speed and required degree of accuracy based on the task constraints (for example, lifting up a cup without spilling it).

Question 63

What is Spatial Coding?

Answer 63

Prior to initiating limb movements, the brain must map (translate) spatial locations in the environment into a body-centred coordinate system (for example, the left and right sides of the body).

Question 64

What is Rhythmicity?

Answer 64

Prior to engaging in complex coordinated movements (such as hitting a golf ball), the brain will plan the specific timing of the movement sequences (the rhythmic pattern) in advance.

• This is particularly important for serial skills in which several discrete movement components have to occur in a specific sequence.
• One often sees elite performers engaging in performance rituals (routines) prior to the initiation of a complex skill (for example, golfers and baseball players swinging their clubs and bats, respectively, to help prepare the timing of the skill in advance of the actual performance).

Question 65

What is Object Control Parameters

Answer 65

When preparing to interact with objects in the environment, the brain uses visual input to estimate object parameters that are needed to prepare the movement.

• For example, motor unit recruitment and muscle force requirements will be based on estimates of an object’s weight, which in turn will be based on previous experience and visual information about the object’s size, structure and shape.