In my career, I have heard the quote “Consistency is the hobgoblin of little minds” when a client or business owner wanted to do something new, often for the sake of doing something new. The full quote by Ralph Waldo Emerson is ““A foolish consistency is the hobgoblin of little minds.” There is a very important distinction there.
Consistency is essential to reducing the cognitive load of your interface – the mental effort required to complete a task. When a design is consistent, every interaction feels smooth and frictionless. When it is too inconsistent, the user must expend unnecessary effort figuring out the interface instead of completing the work.
Design patterns, like cliches, are used over and over again because they speak to an underlying truth. UI patterns are design solutions to common usability problems. Patterns benefit everyone – users already recognize how to use them from previous exposure, and designers don’t need to reinvent the wheel. Knowing where to find a home button, or how links are styled, or how to interact with a list builder are important to a user because few people sit down with an express goal of “I want to use this interface.” Instead, they want to complete a task, and your interface is either the tool that allows them to accomplish their goal or the roadblock keeping them from getting things done.
On the other hand, inconsistency is not all bad. You need to know when and why to break the consistency without leading to design chaos. There are several reasons you may wish to be inconsistent within your established style or conventions and patterns in the market.
All established patterns were once new. Without stretching our designs, we cannot progress. Doing the same things over and over will yield boring, uniform designs. Sometimes experimentation is necessary to see if social assumptions still hold true. When I first started developing CBT courses, the first module was always “How to Use a Mouse.” Times have changed and many advanced interaction patterns are now considered commonplace.
Sometimes the goal is to slow the user down. A friend of mine, Dr. Steve Fedorko, once floated the controversial idea that sometimes an organization should deter or prevent learning in order to force the user to slow down and contemplate their decisions. Actions with extreme consequences may be designed to change from use to use, so a user cannot mindlessly blast through without considering the consequences.
Intentional inconsistency can draw attention to your site for novelty, but must match the context – having a parallax slider and infinite zoom interface may be flashy, but would not work well for most purposes in a tax preparation organization. For that organization, reducing cognitive burden, streamlining performance and minimizing risk of error has to outweigh a “really bichin’ interface.”
The key, as is most often the case in design, is balance. Consistency does not equal uniformity. Design shouldn’t be a game of templates, but should reflect the usability advantages of existing patterns.