Hick's Law

Hick's Law (for William Edmund Hick) or the Hick–Hyman Law (for Ray Hyman), predicts the time it takes to make a decision in selecting among possible choices. The Hick-Hyman Law measures cognitive information capacity. Given n equally probable choices, the average reaction time T required to choose among them is approximately.

T = b.log2(n+1)

The reaction time curve is logarithmic because for quick search we divide choices into categories, skipping half of choices at each step instead of considering each choice one-by-one. To find a given command in a randomly ordered menu, scanning each command is essential, requiring linear time, so Hick's law does not apply here. But if list is ordered we can search and select by subdividing strategy that works in logarithmic time.

Hick's Law is applicable to menu design. It helps in designing menu hierarchy and depth. When we have too many choices (long hierarchy as shown in the screenshot below) we need to cognitively categorize items to reduce the time taken to select an item at any stage. The logarithmic function of Hick’s Law decides the depth of hierarchy of the menu tree.