Posted on: 20 November 2014
3 Types of Interaction Consistency
Interaction consistency may be one of the most widely accepted pillars of usable interaction design. This seemingly simple concept can act as a double-edged sword and has lead many interface designers to make serious UX design errors in the name of consistency.
Akendi’s 7 Interaction Design Principles, include 3 different types of interaction consistency: System Consistency, Platform Consistency, and Real World Consistency. We devoted a quarter of our list to interaction consistency because consistency is a complex concept and these are three distinct concepts that can compete with one another.
3 Sides of Interaction Consistency
System consistency is what most people think of when the term consistency comes up in interface discussions. Basically, it means that similar functions in your system should look the same, behave the same and be called the same thing. This applies to terminology, visual design, and interaction behaviour. If a radio button in one section of your interface only allows a single selection, then it shouldn’t allow multi-selection in another section. If you call it ‘record’ in one section, it shouldn’t be called ‘save’ somewhere else. System consistency is important because it supports learnability in your users. If they drag-and-drop a file in one part of your system, they will already know they can do it somewhere else. Like all forms of interaction consistency, system consistency can be taken too far.
In the past I have seen interfaces where very different functions look and behave the same. Well-intentioned designers will take consistency so far they will end up making very different things look and behave very similarly. This can actually cause confusion in users who may no longer be able to discern functions. System consistency should only be applied to similar functions and making distinct features distinctive can be just as important as maintaining consistency.
Working across mobile platforms can create all sorts of challenges for interaction designers. The first rule of mobile interaction design is to ensure your designs match the conventions of platform you are designing for. This ensures that if an element in your design looks like something from other systems on the same platform, your users can expect it to behave the same way and mean the same thing. This becomes more challenging when designing responsive solutions, which will inevitably be used on all kinds of mobile platforms.
When constructing multi-platform designs, platform consistency becomes more about avoiding violating platform specific expectations rather than the traditional approach of simply adhering to the platform style guide of whatever system you are working on.
Real World Consistency
To adhere to this type of interaction consistency, elements in the design that look like or have the same name as counter-parts in the external world should function and have the same meaning in the system. Real world consistency has also been referred to as metaphor use with the classic example of the shopping cart. The shopping cart metaphor bridges the gap between the brick and mortar shopping experience and online buying by capitalizing on what users already know about traditional shopping. This design pattern has become so popular it is now being applied out of context. I once worked on an IT requisition system that was struggling with users uptake. It turns out their application of the shopping cart metaphor was actually negatively impacting the usability of the system.
This makes sense, as in the real world, you would never put the request for a new phone line and email address for a new employee in a shopping cart before submitting it to the IT department. As designers, we all too often forget that our systems don’t function in a vacuum and that the people using our systems are not us. Understanding the users’ context and mental model of the task will help ensure your design is consistent with their world. If your users are Australians and they refer to calling someone on the phone as giving them a ‘ring tingle’, then so should your system.
The real challenge comes when trying to create a system that not only needs to work across mobile platforms, but other devices all together (desktop, set-top boxes, gaming consoles, etc.) Here system consistency and platform consistency can come into direct opposition. This challenge can be furthered when these systems are used in very different contexts and by a wide spectrum of users. In the end, all three types of consistency work because they capitalize on users expectations.
Keeping these principles in mind will help guide your initial design, but the only way to ensure your design is matching users expectations is through usability testing with real end users.