KIN 312 CH 6

Fitt’s Law

The faster you try to move a target, the less accurate you become. Movement time depends on how far you are expected to move(A), and how small the target is (W).

Speed accuracy Trade-Off

If you are trying to move faster, accuracy decreases. But if you try to be more accurate, then you would usually move slower.

Linear Speed-Accuracy Trade-Off

Keeping an “average speed” means that the errors stay the same, no matter if the movement is long and slow, or short and quick.

Why do errors increase when MT decreases?

Moving faster requires more muscle force and more force causes more variability and the limb wanders off the intended path.

Exception in forceful movements

When you use more than ~70% of max force, increasing speed can actually make one more accurate rather than less. Accuracy follows the inverted U principle here as medium force is the worst, but low or high force yields better results.

Visual Illusions

The visual environment can make the goal area look off and trick the aiming. 

In golf, the hole might look smaller when surrounding by certain patterns which makes putting harder.

Movement Timing

When the goal is about timing, moving faster can make one more accurate in time. Drumming or clapping along to a beat, the speed can make the rhythm more precise.