speed-accuracy trade off

Explain the two-component control theory for aimed actions

• initial impulse (pre-programmed ballistic drive)

• And the slower control phase which uses sensory feedback to minimise error

• As you get closer to the target feedback can come into balance, but if the movement is rapid there is less time for feedback control so more errors occur causing a speed-accuracy trade off

• As movements get faster or longer accuracy falters

Use Fitts’s reciprocal tapping study to explain the speed-accuracy trade off

• use alternate taps between 2 targets as fast as possible but keeping <5% error

• Manipulate the distance (A) and width (W) whilst measuring movement time

• With a larger A and/or smaller W MY increases systematically

• Then created a law that there is a linear relationship between the ID and MT if ID stays the same (same A:W ratio)

Equations for movement time and index of difficulty

MT=a+b • log2(2A/W)

ID=log2(2A/W)

Why does MT increase with ID?

• with a narrower W more corrections are needed resulting in a longer MT

• if there is a very short MT then there is little time for vision so accuracy would suffer unless you slow down

Give an example of fitts law in football, tennis, rugby or hockey

Football: passing through a gate

Tennis: hitting a forehand shot into a specific landing zone

Rugby: practicing a kick to a specific zone

Hockey: passing the puck to a teammate

(For all these as W decreases or A increases, MT also increases otherwise accuracy will drop)