Lecture 9

Question 1

when we do things too fast what happens?

Answer 1

-accuracy decreases-effectiveness at the task decreases
-Woodworth (1899) Wooden drum experiment: the longer the line, the speed of the task increased, the accuracy decreased
Paul Fitts described the mathematical principals of speed and accuracy (Fitts’s law)

Question 2

Fitts reciprocal tapping task

Answer 2

• played with the concepts of amplitude (A) and width (W)
• Movement time (MT) is constant whenever the ratio of amplitude to target width remains constant
• Index of difficulty (ID): mathematical construct that defines the difficulty of different variations of the A and W combinations

Question 3

speed accuracy trade off

Answer 3

• we give up speed in order to be more accurate with our movements
• where do we see this in everyday life
• holds true in many different scenarios, with different populations of individuals
  1. Visual: looking at the target, helps us guide our movements, optic flow: changing between the two targets
  2. Closed loop: during the process of moving between the targets Open loop: the actual tapping and speed

Question 4

linear speed accuracy trade off

Answer 4

• when aiming for a target endpoint, Fitts hold true as well
• Increased A results in a decrease in accuracy at endpoint (around the target)
• consider MT- when MT increases, accuracy down
• instructions are important: quickly and accurately or as quick as possible or as accurately as possible: specificity of instructions

Question 5

error in rapid movements

Answer 5

• activation of muscle units-a “noisy” process
• the relative contraction forces of the participating muscles of the limb are a major factor in determining the trajectory of the limb
• the amount of forces applied are, to an extent, variable and unpredictable
• inconsistency INCREASES with increased force

Question 6

we dont always use one arm/hand /limb to perform a task, then what?

Answer 6

1. Bimanual aiming tasks
   a) congruent tasks: two hands moving the same way to the two exact same targets: MT should be similar between two hands
   b) incongruent tasks: two hands are doing two different things, left hand to the shorter target: MT should be different
   - demonstrates that the MT and kinematics of the limbs does not work independently from the other limb, but by a joint command

Question 7

complex coordination patterns

Answer 7

• IN-phase: wiggle pointers fingers in front of you, both go inward towards the midline
• ANTI-phase: wiggle your pointer fingers with both going the same direction at the same time

Question 8

what about switching between the two phases (inphase and antiphase)

Answer 8

• switching from in-phase to anti-phase takes longer than the opposite
• IN-phase: one coordination pattern is used, reducing the demand for attentional control
• ANTI-phase: two separate patterns being used; demand on attention

Question 9

revisiting speed accuracy trade off

Answer 9

• when the motor system is threatened by an increase in speed, the motor system may seek out a different, more stable coordination patterns
• accuracy will not continue to diminish with speed
• stability is sought: therefore, coordination patterns change to re-establish stability

Question 10

-when speed increases, resulting in decreased accuracy, the motor system has 3 options:

Answer 10

1. Reduce the speed to maintain accuracy
2. Decrease accuracy and maintain speed
3. Maintain the speed and change the movement pattern in order to re-establish stability