Fitts' law demonstrates that the movement time to a target depends on the size of and the distance to the target

A model of human psychomotor behavior that correlates an index of difficulty with the time to complete a movement task

background

• Paul Fitts, 1954
• Worker efficiency
  • Production lines
  • Assembly tasks
• Design better to reduce human lives lost
• Models production in aimed movement

equation

• Index of performance (IP)

• Index of difficulty (ID)

• Movement time (MT)

• Target width (W)

• Target amplitude (A) i.e. distance travelled

• Fitts’ law equation: where a and b are regression coefficients $IP=ID/MT$ $ID=lo{g}_2(2A/W)$ $MT=a+blo{g}_2(2A/W)$

• Shannon formulation (most commonly used now)

$$MT=a+b{\log }_2(A/W+1)$$