User-centered design (UCD) is a design philosophy and a process in which the needs, wants, and limitations of end users of a product are given attention at each stage of the design process.
User-centered design can be characterized as a multi-stage problem solving process that not only requires designers to analyze and foresee how users are likely to use a product, but also to test the validity of their assumptions with regards to user behaviour in real world tests with actual users.
Such testing is necessary as it is often very difficult for the designers of a product to understand intuitively what a user of their design experiences, and what each user's learning curve may look like. The main difference from other product design philosophies is that user-centered design tries to optimize the product around how users can, want, or need to use the product, rather than forcing the users to change their behavior to accommodate the product.
For example, the user-centered design process can help software designers to fulfill the goal of a product engineered for their users. User requirements are considered right from the beginning and included into the whole product cycle. These requirements are noted and refined through investigative methods including: ethnographic study, contextual inquiry, prototype testing, usability testing and other methods.
Generative methods may also be used including: card sorting, affinity diagraming and participatory design sessions. In addition, user requirements can be understood by careful analysis of usable products similar to the product being designed.
UCD answers questions about users and their tasks and goals, then uses the findings to make decisions about development and design. UCD of a web site, for instance, seeks to answer the following questions:
- Who are the users of the document?
- What are the users’ tasks and goals?
- What are the users’ experience levels with the document, and documents like it?
- What functions do the users need from the document?
- What information might the users need, and in what form do they need it?
- How do users think the document should work?
As examples of UCD viewpoints, the essential elements of UCD of a web site are considerations of visibility, accessibility, legibility and language.
Visibility helps the user construct a mental model of the document. Models help the user predict the effect(s) of their actions while using the document. Important elements (such as those that aid navigation) should be emphatic. Users should be able to tell from a glance what they can and cannot do with the document.
Users should be able to find information quickly and easily throughout the document, regardless of its length. Users should be offered various ways to find information (such as navigational elements, search functions, table of contents, clearly labeled sections, page numbers, color coding, etc). Navigational elements should be consistent with the genre of the document.
"Chunking" is a useful strategy that involves breaking information into small pieces that can be organized into some type meaningful order or hierarchy. The ability to skim the document allows users to find their piece of information by scanning rather than reading. Bold and italic words are often used.
Text should be easy to read: Through analysis of the rhetorical situation, the designer should be able to determine a useful font style. Ornamental fonts and text in all capital letters are hard to read, but italics and bolding can be helpful when used correctly. Large or small body text is also hard to read. (Screen size of 10-12 pixel sans serif and 12-16 pixel serif is recommended.) High figure-ground contrast between text and background increases legibility. Dark text against a light background is most legible.
Depending on the rhetorical situation, certain types of language are needed. Short sentences are helpful, as well as short, well-written texts used in explanations and similar bulk-text situations. Unless the situation calls for it, do not use jargon or technical terms. Many writers will choose to use active voice, verbs (instead of noun strings or nominals), and simple sentence structure.
A user-centered design is focused around the rhetorical situation. The rhetorical situation shapes the design of an information medium. There are three elements to consider in a rhetorical situation: audience, purpose, and context.
The audience is the people who will be using the document. The designer must consider their age, geographical location, ethnicity, gender, education, etc.
The purpose is what the document is targeting to or what problem is the document trying to address.
The context is the circumstances surrounding the situation. The context often answers the question: What situation has prompted the need for this document? Context also includes any social or cultural issues that may surround the situation.
User-centered design involves simplifying the structure of tasks, making things visible, getting the mapping right, exploiting the powers of constraint, and designing for error.