Consistency has to be maintained in the system as a whole. It will make your design better, easier to use, and practically invisible. Consistency gives the user plenty of room to experience the design in the way you intend. We should design with this in mind. When someone visits a site for the first time, that’s a new experience. You can make the experience look and feel the same as others but, ultimately, it’s different because the core product is (hopefully) different.
Consistency is the thread that ties together elements in a single design. It also ties together designs across a single campaign or brand, creating a product that is distinguishable, usable, and effective. Within Human-Computer Interaction, it has long been speculated that inconsistency impedes the user experience. However, defining and categorizing consistency has been shown to be a challenging task. Several studies on the subject have categorized consistency with mixed perspectives of the system, its developer, and its user. The article considers only the user perspective and categorizes consistency into physical and conceptual. Let's see have a look at the difference.
Physical consistency
Both operational and representational consistency is crucial in interaction design. Operationally, the system should support only a few ways of issuing commands. For example, in a direct manipulation system, the user usually selects an object and then specifies the action on that object. In menu systems, the user usually selects the menu function and then specifies the required object through further dialogue. Two methods are employed, but each member of the object class is treated consistently. In addition to consistency of operations, a consistent representation should be employed. For example, error messages should look the same and appear in a consistent place on the display in relation to the rest of the dialogue In general objects in a class should appear in the same style.
Conceptual consistency
There are a number of aspects to conceptual consistency. Firstly, a consistent metaphor should be chosen. This extends to the level of abbreviations and design of icons. Users will bring knowledge of the external world to human-computer interaction and thus the system should be consistent with their expectations. For example, "D" would be a poor candidate for a "SAVE" command because it does not suggest the correct meaning, whereas "S" would be much better for a system designed for English-speaking people. Icons should be designed to exploit an appropriate metaphor in the user interface. Metaphorical consistency is heavily culture-dependent. Secondly, entities within the same class, or performing a similar role, should be treated consistently. for example, deletion of a word should have the same syntactic form as deletion of a paragraph, and selecting a word should have the same form as selecting a paragraph. This means that users should be able to anticipate correctly how they should specify these operations and how the system will respond. However, it is not always easy to establish when entities do have this type of similarity. Thirdly, we can identify task consistency; that is, the task allocation has been carried out in a consistent way so that the user has to perform similar tasks on similar objects.
Conclusion
Although consistency is an important goal in HCI design, it is not easily achievable. Consistency for the learner may not be consistent for the expert. Consistency for the discretionary user may not be consistent for the dedicated user. In general, since different people have different experiences to bring to the interaction, they may perceive as inconsistent what the designer perceives as consistent.
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