Much like proximity, using similarity in interaction design can help users understand how different elements are related. Those elements can have similar meanings or functions. 

Similarity in Interaction Design

The law of similarity states that "when things appear to be similar to each other, we group them together and we also tend to think they have the same function."

University of Michigan - Ann Arbor

The Gestalt Principles of Design are guidelines that assist in creating user-centered design. They were first proposed after studying human perception and behavior. These principles can apply to all elements of design, including interaction and interface design. 

Gestalt Principles of Design

"What are Gestalt Principles?" Interaction Design. https://www.interaction-design.org/literature/topics/gestalt-principles

The law of proximity states that "things that are close together appear to be more related than things that are spaced farther apart." 

The Law of Proximity

The Law of Similarity

The law of common region states that when objects are located within the same closed region, we perceive them as being grouped together. This is very similar to the law of proximity, however it happens in a closed area. 

The Law of Common-Region

The law of focal point states that "whatever stands out visually will capture and hold the viewer’s attention first."

The Law of Focal Point

The law of continuity, also referred to as good continuation, is a Gestalt principle suggesting that individuals are more prone to perceive lines as continuous and smoothly flowing rather than as disconnected, jagged, or broken segments.

The Law of Continuity

 The closure principle states that "Individuals perceive objects such as shapes, letters, pictures, etc., as being whole when they are not complete." People look for a recognizable pattern, and we fill in the gaps.

The Law of Closure

The figure-ground principle states that "people instinctively perceive objects as either being in the foreground or the background." The user knows that the foreground is more important than the background.

The Law of Figure-Ground

The symmetry principle states "Symmetric elements give the user the feeling that everything is ordered." This helps a user feel more comfortable using a website. 

The Law of Symmetry

The common fate principle states that "elements moving towards the same direction are perceived as more related than those moving in different directions, or not moving at all."

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