Lecture 5 - Speed and Accuracy Principles

Question 1

Describe the Fitts’ Paradigm

Answer 1

Measuring movement time, focus on accuracy not speed
logarithmic relationship between movement time and distance of movement
Inverse relationship between difficulty of movement in speed
Shows how MT is sacrificed off under different values of ID to maintain accuracy

Question 2

What does Fitts’ Law hold for?

Answer 2

Everything
Different movements (larger limbs more sensitive to change in Index of Difficulty)
underwater
age
lower body
imagined movements

Question 3

Describe the Linear Speed-Accuracy Trade off

Answer 3

single aiming movement
MT constrained
focus on speed rather than accuracy
Measuring standard deviation of movement amplitude (difference in end point)
As distance increases, errors increse
As MT decreases, errors increase
As MT decreases, velocity increases, and errors increase

Question 4

What are the two ways to explain the linear versus logarithmic relationship?

Answer 4

Feedback Hypothesis
Linear is a preprogrammed task, so feedforward and open loop
Logarithmic is for continuous tasks, so closed loop and receives feedback for corrections
Movement-time Goal Hypothesis
Since the two paradigms are fundamentally different (be as fast as possible vs adopt non corrective strategy) so that’s why there is a different relationship

Question 5

Temporal speed-accuracy trade-off

Answer 5

Anticipation (batter)
As MT decreases or velocity increases, accuracy improves
Discrete = produce specific MT
Smaller MT, larger velocity produces more consistency