Module 6

Question 1

What does Fitts’ law mean?

Answer 1

Movement time is constant whenever the ratio of the movement amplitude to target width remains constant
Movement time increases as the ratio of A to W increases by making A larger, W smaller, or both

Question 2

Example of Fitts’ law

Answer 2

Alternative tapping two targets that are A (target distance) apart and are W (target width).
There is a home position in the middle where the person starts.
The farther away they are (increased A), the slower the movement time will be.
The thinker the targets are (decreased W), the slower the movement time is with good accuracy (bad accuracy with static speed).

Question 3

Linear Speed-Accuracy Trade-Off

Answer 3

Suggests that for various combinations of A and MT, that has a constant ratio (constant average velocity), the aiming errors are about the same

Question 4

As movement velocity increases…

Answer 4

Errors increase linearly

Question 5

How to maintain movement accuracy in rapid tasks?

Answer 5

Trading off with increases in movement distance and decreases in movement time

Question 6

Why does increasing the speed of rapid movement lead to inaccuracy?

Answer 6

The contraction forces of the various muscles being used determine the the resulting trajectory of the moving limb

Question 7

When does inconsistency in forces increase?

Answer 7

When the forces increase

Question 8

Inconsistencies

Answer 8

Noise

Variability

Question 9

Example of inconsistencies

Answer 9

Record players are preprogrammed with music but many things (scratching, warping) can affect its ability to play that music

Question 10

When is more force required?

Answer 10

When the movement time decreases

When the amplitude increases

Question 11

What does more force lead to?

Answer 11

More variability because it causes the movement to deviate from the intended trajectory that leads to more inaccuracy

Question 12

What happens when a movement requires very high levels of muscular contractions?

Answer 12

Increased speed by reducing movement time can decrease spatial and timing errors

Question 13

When is one most accurate?

Answer 13

At low force (slow) and high force (fast)

Question 14

Temporal time =

Answer 14

When

Question 15

How does one make movements more temporally accurate?

Answer 15

Decreasing movement time (moving faster)

Question 16

Bimanual Fitts’ Task

Answer 16

Both limbs could be assigned identical tasks with either low or high IDs or to different (incongruent) tasks

Question 17

When is the explanatory power of Fitts’ Law reduced?

Answer 17

When separate and incongruent task demands are required of two limbs

Question 18

Gamma-V Experiment

Answer 18

W separate motor programs

Can’t be run at the same time without considerable interference

Question 19

What is similar to the gamma-v experiment?

Answer 19

Patting head/rubbing stomach

Question 20

Continuous Bimanual Timing

Answer 20

Controlling the continuous movement of two limbs (each with its own spatial/temporal goal)

Question 21

What can the executive do?

Answer 21

Use a common movement command to control the movements of both limbs
Switch attention rapidly between the executions of the two tasks

Question 22

Why can the executive do those things?

Answer 22

The movements are ongoing

Question 23

ID

Answer 23

Index of difficulty

Defines the difficulty of the various combinations of A and W

Question 24

Speed-Accuracy Trade-Off

Answer 24

Tendency for people to “give up” speed in order to trade speed off for acceptable levels of accuracy

Question 25

Why are slower movements more accurate?

Answer 25

There is more time to detect errors and to make corrections

Question 26

When does movement time lengthen?

Answer 26

When the number of corrections to be made increases

Question 27

When does the speed-accuracy trade-off usually occur and why?

Answer 27

Usually in slow, closed-loop actions bc one has to be able to make the corrections

Question 28

What happens when performance accuracy (stability) is threatened by increased speed?

Answer 28

A motor system seeks a more stable coordination pattern to take its place
Doesn’t let accuracy keep diminishing with the increasing speed and the coordination changes so stability can be reestablished

Question 29

What can the motor system do when increased speed leads to decreased accuracy? (3)

Answer 29

Reduce speed and maintain accuracy
Decrease accuracy and maintain speed
Maintain speed and change the movement pattern in order to reestablish stability