Hick's Law (Hick-Hyman Law)
Decision time grows logarithmically with the number of options you can choose from.
William Edmund Hick and Ray Hyman
In the equation below, T is the time to make a decision, n is the number of options, and b is a constant which is determined by analysis of the data.
This law only applies when the number of options is ordered, for example, alphabetically. This is implied in the base two logarithm - which implies the decision maker is essentially performing a binary search. If the options are not well ordered, experiments show the time taken is linear.
This is has significant impact in UI design; ensuring that users can easily search through options leads to faster decision making.
A correlation has also been shown in Hick's Law between IQ and reaction time as shown in Speed of Information Processing: Developmental Change and Links to Intelligence.
See also: