KINE 2P05 Study Guide - Final Guide: Touchpad, Binary Logarithm, Motor Skill
19 Dec 2016
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Lecture 6 Review
Lecture 6 – Principles of Speed & Accuracy
o Speed-accuracy trade-off
o For tasks that benefit from speed and accuracy, there is a tradeoff when
emphasizing one over the other
▪ Increased speed results in decreased accuracy
▪ To improve accuracy you must decrease speed
o Fitts’ Law
o Describes a mathematical principle of speed and accuracy
o The relation between the amplitude of the movement, the size of the
target, and the resulting average movement time can be described as:
o MT = a + b [log2 (2D/W)]
o MT increases as movement amplitude (D) increases
o MT increases as the accuracy requirement increases
▪ As W decreases
o MT is ~constant for tasks with the same ID
▪ Ratio of D:W remains constant
o These principles are valid for a wide variety of conditions, individual
variables, task paradigms, and effectors
o Movement Time proportional to index of difficulty (size & distance) – What
changes ID?
▪ That means that the task difficulty is similarly affected by
manipulations of either movement distance or target size
▪ MT remains constant when D:W remains constant
▪ Long movements to wide targets ≈
▪ Short movements to narrow targets
o Evidence for Fitts’ Law
▪ Task
• Typing on keyboards (computer, phone, etc.) –
Aiming with mouse, trackpad, etc.
• Golf, basketball
• Effectors
▪ Individual
• Children, older adults
• Patients with movement disorders (ex. Parkinson’s Disease)
▪ Environment
• Underwater
• In outer space
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