Fitts and Hick's Law in User Interface Design

What Are Fitts' and Hick's Laws?

Fitts' law is a principle in human–computer interaction that predicts the time it takes for a user to move to a target area, based on the distance between the starting point and the target. The law states that the time required to rapidly move to a target area is proportional to the logarithm of the ratio of the target size (T) to the distance from the starting point (D). Mathematically, this can be expressed as T = a + b log2(1 + D/T), where 'a' and 'b' are constants.

Hick's law, on the other hand, describes how the time it takes for a person to make a decision increases with the number of choices available. The law states that the time required to choose among n alternatives is given by T = b + k log2(n), where 'b' and 'k' are constants.

Why Do These Laws Matter?

Fitts' and Hick's laws matter in user interface design because they help predict the time users will need to interact with elements on a screen. By understanding these principles, designers can create more efficient and intuitive interfaces that reduce user frustration and improve overall usability.

For example, when designing a navigation menu, Fitts' law suggests placing frequently used items within easy reach (small D) but not so close as to be ambiguous. Hick's law implies that offering fewer options at once will generally lead to faster decision-making.

Real-World Applications

Fitts' and Hick's laws have been applied in various fields, from software design to industrial ergonomics. In mobile app development, for instance, Fitts' law can guide the placement of buttons and controls to ensure they are easily accessible yet not too close together to avoid accidental taps.

In web design, Hick's law is used to minimize decision fatigue by simplifying navigation menus and reducing the number of choices presented at once. This approach helps users find what they need more quickly.

How Do These Laws Relate to the Simulation?

The Fitts and Hick UX Lab simulation allows you to experiment with different interface layouts, such as rings, lists, grids, or pie menus. By adjusting parameters like item count, target size, spacing, and constants 'a' and 'b', you can observe how these changes affect the time it takes for a model user to interact with the interface.

This hands-on approach helps designers understand the practical implications of Fitts' and Hick's laws in real-world scenarios. For instance, you might find that a grid layout is more efficient than a pie menu when dealing with many items, as the distance between targets can be optimized.

Frequently asked questions

Try it live

Everything above runs in your browser — open Fitts and Hick UX Lab: 2D Interface Screen and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.