Chapter 6: Speed, Accuracy, and Timing Quiz

Questions and Answers

What is the Speed-Accuracy Trade Off?

The tendency for accuracy to increase as speed increases

The ability to maintain speed without affecting accuracy

An irrelevant concept in movement analysis

The tendency for accuracy to decrease as movement speed increases (correct)

What is Fitt's Law?

The principle that movement time in aiming tasks is linearly related to Log2(2A/W)

What does Index of Difficulty (ID) represent?

The theoretical difficulty of a movement in the Fitts tapping task, calculated as ID = Log2(2A/W)

What is Amplitude (A) in aiming tasks?

The distance between the two target centers Signup and view all the answers

What is Width (W) in the context of aiming tasks?

The size of the target Signup and view all the answers

How do we predict Movement Time (MT) using Fitt's Law?

MT = a + bLog2(2A/W) Signup and view all the answers

What is Effective Target Width (We)?

The variability of movement endpoints about a target; represents effective target size Signup and view all the answers

What does Schmidt's Law state?

Aiming errors are similar for various combinations of movement amplitude and MT with a constant ratio Signup and view all the answers

What is the Linear Speed-Accuracy Trade Off?

Increases in A and decreases in MT can be traded off to maintain movement accuracy Signup and view all the answers

Why do rapid movements tend to produce more errors?

Variability in performance is caused by inconsistent processes converting CNS impulses to muscle activation Signup and view all the answers

How does noise affect accuracy in fast movements?

The presence of noise means actual forces produced are inconsistent with intended movements; noise increases with force Signup and view all the answers

Explain noise using the hammer and nail example.

Muscles act at various angles and misalignment can result in missed targets due to force errors Signup and view all the answers

What are the reasons increasing speed increases error, according to Schmidt's Law?

Inconsistency of forces increases with more force needed, leading to variability and errors Signup and view all the answers

What are the relationships between movement speed, distance, and accuracy?

MT will increase as A increases or W decreases Signup and view all the answers

What are Woodworth's two component model phases?

Initial ballistic phase and homing in phase Signup and view all the answers

Which of the following are exceptions to the Speed-Accuracy Trade-Off?

Extremely rapid and forceful movements Signup and view all the answers

Explain how very forceful movements are exempt from the Speed-Accuracy Trade-Off.

Increasing force and decreasing MT can reduce variability in force outputs Signup and view all the answers

How do visual illusions serve as an exception to the Speed-Accuracy Trade-Off?

They can deceive the brain, leading to more accurate or erroneous movements Signup and view all the answers

Explain how timing is an exception from the Speed-Accuracy Trade-Off.

Greater accuracy occurs at shorter durations due to less noise interference Signup and view all the answers

Study Notes

Speed-Accuracy Trade Off

Accuracy decreases as movement speed increases; achieving both requires a compromise.
Slower movements yield higher accuracy, while faster movements tend to be less accurate.

Fitt's Law

Movement time (MT) in aiming tasks relates to the logarithmic formula Log2(2A/W); where A is amplitude (distance) and W is target width.
This law helps predict the time required to aim accurately.

Index of Difficulty (ID)

Defined as ID = Log2(2A/W); measures the difficulty of a movement in Fitts' tapping task.

Amplitude (A)

Represents the distance between two target centers in aiming tasks.

Width (W)

Indicates the size of the target involved in aiming tasks.

Predicting MT Using Fitt's Law

MT can be calculated using the formula MT = a + bLog2(2A/W).

Effective Target Width (We)

Represents the variability of movement endpoints about a target, which affects perceived target size.
Calculated as the within-subject standard deviation of movement distances over multiple attempts.

Schmidt's Law

Suggests consistency in aiming errors across different combinations of movement amplitude and MT that maintain a constant average velocity.

Linear Speed-Accuracy Trade Off

Explains that increases in amplitude and decreases in MT can occur simultaneously while maintaining movement accuracy.

Variability in Rapid Movements

Rapid movements lead to more errors primarily because there is insufficient time for feedback and corrections.
The inconsistency in muscle activation processes contributes to this variability.

Understanding Noise in Fast Movements

"Noise" refers to inconsistencies in motor program execution, leading to discrepancies in intended forces and resultant movements.
Noise tends to increase with greater force application, particularly beyond 70% of maximal force.

Noise Example: Hammer and Nail

In hammering a nail, various muscle groups exert forces at different angles; inaccuracies in force application can lead to missing the target.

Speed Increases and Errors

Forces from multiple muscles determine movement trajectory; as more force is required for rapid movements, variability also increases, leading to potential errors.

Relationships Between Movement Speed, Distance, and Accuracy

MT increases when either the target amplitude (A) increases or the target width (W) decreases.

Woodworth's Two-Component Model

Describes the process of hitting a target comprising two phases:
- Initial ballistic phase
- Homing in phase

Exceptions to the Speed-Accuracy Trade Off

Certain scenarios where S-A trade-off does not apply include:
- Extremely rapid and forceful movements
- Targets affected by optical illusions
- Critical timing accuracy requirements

Forceful Movements Exception

Very forceful movements yield lower variability due to maximal effort, resulting in increased accuracy.
An inverted-U relationship exists, with least accuracy at moderate force levels.

Visual Illusions as an Exception

Optical illusions can enhance perceived accuracy or yield increased errors due to brain misinterpretation.

Movement Timing as an Exception

Time-sensitive movements are performed more accurately in shorter durations, with reduced opportunities for noise interference.
Halving MT can also cut timing errors in half.

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Description

Test your understanding of the principles of speed, accuracy, and timing in movements. This quiz covers key concepts such as the speed-accuracy trade-off and Fitt's Law, which are essential for mastering movement skills. Prepare to enhance your knowledge with these critical principles.