Fundamentals of User-Centered Design

UCD is an approach used in computer systems design. Its purpose is to address

these fundamental questions: ‘How do I understand the user?’ and ‘How do I ensure

this understanding is reflected in my system?’ [10]. In order to create a usable and

successful final product, the design process positions the end user at the center to

ensure the user can easily use the system to meet his or her needs [11]. Vredenburg et

al. defines UCD as the practices of “the active involvement of users for a clear

understanding of user and task requirements, iterative design and evaluation, and a

multidisciplinary approach” [12]. The system does not require users to adapt their

behaviors to use; instead, it is designed to support its users’ existing behaviors.

The techniques and ideas of UCD came from the early works of Gould and

Lewis (1985) [11] and Norman and Draper (1986) [13]. At that time, Gould and

Lewis proposed and discussed three basic principles for this emerging field: (1) an

early focus on understanding users and their tasks; (2) empirical measurement of

prototype by representative users; and (3) an iterative cycle of design, test and

measure and redesign. In 1988 Norman [14] further elaborated UCD and he suggested

every good design should follow these four main principles:

1. Make it easy to determine what actions are possible at any moment.

2. Make things visible, including the conceptual model of the system, the

alternative actions, and the results of actions.

3. Make it easy to evaluate the current state of the system.

4. Follow natural mappings between intentions and the required actions;

between actions and the resulting effect; and between the information that is

visible and the interpretation of the system state.

In addition to this, Norman also suggested the following seven design rules are

essential to facilitate the designer’s tasks:

1. Use both knowledge in the world and knowledge in the head. This principle

is based on the theory of mental models. The designer has a conceptual

model about the system, and during the use the user also develops a mental

model explaining the operation of the system. For the system to succeed, the

designer’s model must match with the user’s mental model. However, the

designer does not talk directly to the user. The designer can only

communicate with the user through the "system image”. The system image

is the designer’s materialized mental model, such as the system’s

appearance, operation, or the manuals included with it. The designer must

ensure that the system image is consistent with his or her conceptual model.

2. Simplify the structure of tasks. Tasks should be simple. Avoid requiring

difficult actions like planning and problem solving in them. Consider the

limits of the user’s short-term memory (STM) and long-term memory

(LTM). On average the user is able to remember five to nine unrelated

things at a short time. Keep the task consistent and provide mental aids for

easy retrieval of information from LTM.

3. Make things visible: bridge the gulfs of execution and evaluation. Consider

Norman’s stages model of actions in Figure 3.1. The left side of the figure

(intention to act, sequence of actions, and execution of actions) is the

execution part. The user interface should provide information for the user to

decide which actions he or she should undertake. The right side of the figure

(perceiving the state of the world, interpreting the perception, and

evaluation of the perception) is the evaluation part. The user interface

should provide feed to show the user what can be done and what the results

are.

Figure 3.1 Norman’s stages model of actions.

4. Get the mappings right. A natural mapping that leads to immediate

understanding should be used. The representation of the control’s

functionality should be made with careful considerations of cultural

standards and physical analogies.

5. Exploit the power of constraints, both natural and artificial. Design the

system to make the user feel that there is only one action possible or logical

to do.

6. Design for error. Assume that the user will make errors. The system should

be designed to allow the users to recover from any possible error made.

7. When all else fails, standardize. Create a universal standard for things

cannot be explained in any logical or culturally determined way.

In 1999 an international standard ISO 13407 was release, entitled

‘Human-Centered Design Processes for Interactive Systems’, providing a

standardized description of UCD [15]. ISO 13407 provides guidance for achieving a

high level of usability through UCD actions and strategies. This standard describes an

iterative cycle of development composed of five main activities of UCD. Four of

these activities are performed iteratively until the outcome meets the initially set

objectives. Every UCD project should carry out these activities from the beginning.

These activities are listed below and presented in Figure 3.2:

1. Plan the human centered process.

2. Understand and specify the context of use.

3. Specify the user and organizational requirements.

4. Produce design solutions.

5. Evaluate designs against requirements.

Figure 3.2 The five main activities of UCD (adapted from ISO 13407 [15]).

ISO 13407 aims to provide general guidelines for UCD, the detailed description

about the research methods and techniques required to conduct these activities is not

included [16]. In fact, there are many research methods and techniques available for

UCD, with Table 3.1 presenting a selection of them, grouped by the four main

activities described above. The detailed discussion about each of these methods is not

within the scope of this thesis, instead, only the details of those been selected and

considered for this research will be included in below and following chapters.

Table 3.1 Research methods for UCD (adapted from [17, 18, 19, 21, 20]).