The Consistency principle says that systems are more useable and learnable when similar parts are expressed in similar ways. Consistency allows the learning of new concepts quickly by transferring the knowledge of previous concepts learned in a similar method. Consistency can be categorised in four parts: aesthetic, functional, internal and external.
“A consistent interface is one that follows rules, such as using the same operation to select all objects. For example, a consistent operation is using the same input action to highlight any graphical object at the interface, such as always clicking the left mouse button” (Preece and Rogers, 2002).
Aesthetic consistency implies a consistent application of style and appearance, promoting recognition and an emotional relationship on behalf of the viewer.
“Consistency is an important consideration in branding too – using the same typefaces, logos, colours, features, uniforms and architecture improves brand recognition, reduces costs and establishes a stronger relationship with customers” (Doctor Disruption 2013).
Functional consistency refers to the consistency of meaning and action. The use of functional consistency enables the viewer to apply pre existing knowledge in understanding how the design works. i.e. Apple Mackintosh computers use the traffic light icons within their operating system.
“Consistency in design is about making elements uniform — having them look and behave the same way…the designer is looking for a way to leverage the usability by creating uniformity” (Spool ,2005)
Internal consistently refers to consistency with other elements within a larger system. Consistency has already been established in the viewer and so new concepts within the system are now easier to comprehend. Good design implies internal consistency.
“As companies design more for usability and understanding, they will discover a competitive edge, for these principles save customers time and money while increasing morale”
External consistency refers to consistency across other systems in the broader environment. This is difficult to achieve due to the fact that different systems rarely subscribe to the same design language.
An example of Aesthetic consistency:
Coca-Cola have had maintained a strong brand image while being at the front rank of the market. This is due to a ubiquitous use of the colour red and its denotation of strength and vibrancy, as well an appealing logo. It is interesting to see here that Coke are establishing a consistency of image and aesthetics within their own product line. The homogenisation of aesthetics shared across the product range sends the message to consumers that they can expect the same standards in new products that are familiar in original Coke.
An example of Internal consistency:
This jigsaw puzzle is an example of Internal consistency. Two pieces can be joined together in the same way as larger chunks which allows the user to progress through the puzzle.
An example of Functional Consistency:
This control panel from a motor boat relies upon the users prior understanding that the dials are to read from left to right.
Doctor Disruption. (2013). Principles of Design. Retrieved from http://www.doctordisruption.com/design/principles-of-design-52-consistency/
Norman, D. (1990). The Design of Everyday Things. New York, NY: Doubleday.
Preece, J., Rogers, Y., Sharp, H. (2002), Interaction Design: Beyond Human-Computer Interaction. New York: Wiley.
Spool, J. (2005). Consistency In Design. Retrieved from http://www.uie.com/brainsparks/2005/09/15/consistency-in-design-is-the-wrong-approach/