What is Human Computer Interaction
Human-computer interaction (HCI) is a multidisciplinary field of study focusing on the design of computer technology and, in particular, the interaction between humans (the users) and computers. While initially concerned with computers, HCI has since expanded to cover almost all forms of information technology design.
Design rules for interactive systems
Design rules for interactive systems can be supported by psychological, cognitive, ergonomic, sociological, economic or computational theory, which may or may not have roots in empirical evidence. Designers do not always have the relevant background in psychology, cognitive science, ergonomics, sociology, business or computer science necessary to understand the consequences of those theories in the instance of the design they are creating. The design rules are used to apply the theory in practice. Often a set of design rules will be in conflict with each other, meaning that strict adherence to all of them is impossible. The theory underlying the separate design rules can help the designer understand the trade-off for the design that would result in following or disregarding some of the rules. Usually, the more general a design rule is, the greater the likelihood that it will conflict with other rules and the greater the need for the designer to understand the theory behind it.
Principles of Learnability
Predictability of an interactive system means that the user’s knowledge of the interaction history is sufficient to determine the result of his future interaction with it.
When an operation changes some aspect of the internal state, it is important that the change is seen by the user. The principle of honesty relates to the ability of the user interface to provide an observable and informative account of such change. In the best of circumstances, this notification can come immediately, requiring no further interaction initiated by the user. At the very least, the notification should appear eventually, after explicit user directives to make the change observable.
This experience is obtained both through interaction in the real world and through interaction with other computer systems. For a new user, the familiarity of an interactive system measures the correlation between the user’s existing knowledge and the knowledge required for effective interaction.
The generalizability of an interactive system supports this activity, leading to a more complete predictive model of the system for the user. We can apply generalization to situations in which the user wants to apply knowledge that helps achieve one particular goal to another situation where the goal is in some way similar. Generalizability can be seen as a form of consistency.
Consistency relates to the likeness in behavior arising from similar situations or similar task objectives. Consistency is probably the most widely mentioned principle in the literature on user interface design. ‘Be consistent!’ we are constantly urged. The user relies on a consistent interface. However, the difficulty of dealing with consistency is that it can take many forms. Consistency can be expressed in terms of the form of input expressions or output responses with respect to the meaning of actions in some conceptual model of the system.
Principles of Flexibility
Allowing the user freedom from artificial constraints on the input dialog imposed by the system
Ability of the system to support user interaction pertaining to more than one task at a time
The ability to pass control for the execution of a given task so that it becomes either internalized by the user or the system or shared between them
Allowing equivalent values of input and output to be arbitrarily substituted for each other
Modifiability of the user interface by the user or the system
Principles of Robustness
Ability of the user to evaluate the internal state of the system from its perceivable representation
Ability of the user to take corrective action once an error has been recognized
How the user perceives the rate of communication with the system
The degree to which the system services support all of the tasks the user wishes to perform and in the way that the user understands them
Standards and Guideline for Interactive systems
Standards for interactive system design are usually set by national or international bodies to ensure compliance with a set of design rules by a large community. Standards can apply specifically to either the hardware or the software used to build the interactive system.
Underlying theory Standards for hardware are based on an understanding of physiology or ergonomics/human factors, the results of which are relatively well known, fixed and readily adaptable to design of the hardware.
Change Hardware is more difficult and expensive to change than software, which is usually designed to be very flexible. Consequently, requirements changes for hardware do not occur as frequently as for software. Since standards are also relatively stable, they are more suitable for hardware than software.
We have observed that the incompleteness of theories underlying the design of interactive software makes it difficult to produce authoritative and specific standards. As a result, the majority of design rules for interactive systems are suggestive and more general guidelines. Our concern in examining the wealth of available guidelines is in determining their applicability to the various stages of design.
Shneidermans’s 8 Golden Rules
Shneiderman’s eight golden rules provide a convenient and succinct summary of the key principles of interface design. They are intended to be used during design but can also be applied, like Nielsen’s heuristics, to the evaluation of systems. Notice how they relate to the abstract principles discussed earlier.
1. Strive for consistency in action sequences, layout, terminology, command use and so on.
2. Enable frequent users to use shortcuts, such as abbreviations, special key sequences and macros, to perform regular, familiar actions more quickly.
3. Offer informative feedback for every user action, at a level appropriate to the magnitude of the action.
4. Design dialogs to yield closure so that the user knows when they have completed a task.
5. Offer error prevention and simple error handling so that, ideally, users are prevented from making mistakes and, if they do, they are offered clear and informative instructions to enable them to recover.
6. Permit easy reversal of actions in order to relieve anxiety and encourage exploration, since the user knows that he can always return to the previous state.
7. Support internal locus of control so that the user is in control of the system, which responds to his actions.
8. Reduce short-term memory load by keeping displays simple, consolidating multiple page displays and providing time for learning action sequences.
Norman’s 7 Principles
1. Use both knowledge in the world and knowledge in the head.
2. Simplify the structure of tasks.
3. Make things visible: bridge the gulfs of Execution and Evaluation.
4. Get the mappings right.
5. Exploit the power of constraints, both natural and artificial.
6. Design for error.
7. When all else fails, standardize.
Evaluation techniques for interactive systems
What is evaluation
Evaluation role is to access designs and test systems to ensure that they actually behave as we expect and meet user requirements.
Ideally, evaluation should occur throughout the design life cycle, with the results of the evaluation feeding back into modifications to the design.
Goals of evaluation
Evaluation has three main goals: to assess the extent and accessibility of the system’s functionality, to assess users’ experience of the interaction, and to identify any specific problems with the system.
The system’s functionality is important must accord with the user’s requirements.
Evaluation at this level may measuring the user’s performance with the system to assess the effectiveness of the system in supporting the task.
User’s experience of the interaction
How easy the system is to learn, its usability and the user satisfaction with it. It may include his enjoyment and emotional response, particularly in the case of aim to entertainment.
Identify specific problem with the design
This may aspects of the design which, when used in their intended context, cause unexpected results, or confusion amongst user.
Evaluation through expert analysis
evaluation should occur throughout the design process. In particular, the first evaluation of a system should ideally be performed before any implementation work has started. If the design itself can be evaluated, expensive mistakes can be avoided, since the design can be altered prior to any major resource commitments. Typically, the later in the design process that an error is discovered, the more costly it is to put right and, therefore, the less likely it is to be rectified. However, it can be expensive to carry out user testing at regular intervals during the design process, and it can be difficult to get an accurate assessment of the experience of interaction from incomplete designs and prototypes.
The origin of the cognitive walkthrough approach to evaluation is the code walkthrough familiar in software engineering. Walkthroughs require a detailed review of a sequence of actions. In the code walkthrough, the sequence represents a segment of the program code that is stepped through by the reviewers to check certain characteristics
The general idea behind heuristic evaluation is that several evaluators independently critique a system to come up with potential usability problems. It is important that there be several of these evaluators and that the evaluations be done independently.
Design methodologies, such as design rationale , also have a role to play in evaluation at the design stage. Design rationale provides a framework in which design options can be evaluated. By examining the criteria that are associated with each option in the design, and the evidence that is provided to support these criteria, informed judgments can be made in the design.
Evaluation through user participation
Styles of evaluation
Before we consider some of the techniques that are available for evaluation with users, we will distinguish between two distinct evaluation styles: those performed under laboratory conditions and those conducted in the work environment or ‘in the field’.
In the first type of evaluation studies, users are taken out of their normal work environment to take part in controlled tests, often in a specialist usability laboratory
The second type of evaluation takes the designer or evaluator out into the user’s work environment in order to observe the system in action.
Empirical methods: experimental evaluation
One of the most powerful methods of evaluating a design or an aspect of a design is to use a controlled experiment. This provides empirical evidence to support a particular claim or hypothesis. It can be used to study a wide range of different issues at different levels of detail. These include the participants chosen, the variables tested and manipulated, and the hypothesis tested.
The choice of participants is vital to the success of any experiment. In evaluation experiments, participants should be chosen to match the expected user population as closely as possible.
Experiments manipulate and measure variables under controlled conditions, in order to test the hypothesis. There are two main types of variable: those that are ‘manipulated’ or changed and those that are measured
A hypothesis is a prediction of the outcome of an experiment. It is framed in terms of the independent and dependent variables, stating that a variation in the independent variable will cause a difference in the dependent variable.
A popular way to gather information about actual use of a system is to observe users interacting with it. Usually they are asked to complete a set of predetermined tasks, although, if observation is being carried out in their place of work, they may be observed going about their normal duties. Simple observation is seldom sufficient to determine how well the system meets the users’ requirements since it does not always give insight into the their decision processes or attitude.
Another set of evaluation techniques relies on asking the user about the interface directly. Query techniques can be useful in eliciting detail of the user’s view of a system. They embody the philosophy that states that the best way to find out how a system meets user requirements is to ‘ask the user’. They can be used in evaluation and more widely to collect information about user requirements and tasks. The advantage of such methods is that they get the user’s viewpoint directly and may reveal issues that have not been considered by the designer. In addition, they are relatively simple and cheap to administer. However, the information gained is necessarily subjective, and may be a ‘rationalized’ account of events rather than a wholly accurate one. Also, it may be difficult to get accurate feedback about alternative designs if the user has not experienced them, which limits the scope of the information that can be gleaned. However, the methods provide useful supplementary material to other methods. There are two main types of query technique: interviews and questionnaires.
Interviewing users about their experience with an interactive system provides a direct and structured way of gathering information. Interviews have the advantages that the level of questioning can be varied to suit the context and that the evaluator can probe the user more deeply on interesting issues as they arise.
An alternative method of querying the user is to administer a questionnaire. This is clearly less flexible than the interview technique, since questions are fixed in advance, and it is likely that the questions will be less probing.
Evaluation through monitoring physiological responses
One of the problems with most evaluation techniques is that we are reliant on observation and the users telling us what they are doing and how they are feeling. What if we were able to measure these things directly? Interest has grown recently in the use of what is sometimes called objective usability testing, ways of monitoring physiological aspects of computer use. Potentially this will allow us not only to see more clearly exactly what users do when they interact with computers, but also to measure how they feel. The two areas receiving the most attention to date are eye tracking and physiological measurement.
Universal Design for Interactive Systems
Universal design is the process of designing products so that they can be used by as many people as possible in as many situations as possible. In our case, this means particularly designing interactive systems that are usable by anyone, with any range of abilities, using any technology platform. This can be achieved by designing systems either to have built in redundancy or to be compatible with assistive technologies. An example of the former might be an interface that has both visual and audio access to commands; an example of the latter, a website that provides text alternatives for graphics, so that it can be read using a screen reader.
Universal Design Principles
Principle one is equitable use: the design is useful to people with a range of abilities and appealing to all. No user is excluded or stigmatized. Wherever possible, access should be the same for all; where identical use is not possible, equivalent use should be supported. Where appropriate, security, privacy and safety provision should be available to all.
Principle two is flexibility in use: the design allows for a range of ability and preference, through choice of methods of use and adaptivity to the user’s pace, precision and custom.
Principle three is that the system be simple and intuitive to use, regardless of the knowledge, experience, language or level of concentration of the user. The design needs to support the user’s expectations and accommodate different language and literacy skills. It should not be unnecessarily complex and should be organized to facilitate access to the most important areas. It should provide prompting and feedback as far as possible.
Principle four is perceptible information: the design should provide effective communication of information regardless of the environmental conditions or the user’s abilities. Redundancy of presentation is important: information should be represented in different forms or modes (e.g. graphic, verbal, text, touch). Essential information should be emphasized and differentiated clearly from the peripheral content. Presentation should support the range of devices and techniques used to access information by people with different sensory abilities.
Principle five is tolerance for error: minimizing the impact and damage caused by mistakes or unintended behavior. Potentially dangerous situations should be removed or made hard to reach. Potential hazards should be shielded by warnings. Systems should fail safe from the user’s perspective and users should be supported in tasks that require concentration.
Principle six is low physical effort: systems should be designed to be comfortable to use, minimizing physical effort and fatigue. The physical design of the system should allow the user to maintain a natural posture with reasonable operating effort. Repetitive or sustained actions should be avoided.
Principle seven requires size and space for approach and use: the placement of the system should be such that it can be reached and used by any user regardless of body size, posture or mobility. Important elements should be on the line of sight for both seated and standing users. All physical components should be comfortably reachable by seated or standing users. Systems should allow for variation in hand size and provide enough room for assistive devices to be used.
As we have seen in the previous section, providing access to information through more than one mode of interaction is an important principle of universal design. Such design relies on multi-modal interaction. There are five senses: sight, sound, touch, taste and smell.
Sound in the interface
Sound is an important contributor to usability. There is experimental evidence to suggest that the addition of audio confirmation of modes, in the form of changes in keyclicks, reduces errors. Video games offer further evidence, since experts tend to score less well when the sound is turned off than when it is on; they pick up vital clues and information from the sound while concentrating their visual attention on different things. The dual presentation of information through sound and vision supports universal design, by enabling access for users with visual and hearing impairments respectively. It also enables information to be accessed in poorly lit or noisy environments. Sound can convey transient information and does not take up screen space, making it potentially useful for mobile applications.
Touch in the interface
Touch is the only sense that can be used to both send and receive information. Although it is not yet widely used in interacting with computers, there is a significant research effort in this area and commercial applications are becoming available. The use of touch in the interface is known as haptic interaction. Haptics is a generic term relating to touch, but it can be roughly divided into two areas: cutaneous perception, which is concerned with tactile sensations through the skin; and kinesthetics, which is the perception of movement and position. Both are useful in interaction but they require different technologies.
Like speech, we consider handwriting to be a very natural form of communication. The idea of being able to interpret handwritten input is very appealing, and handwriting appears to offer both textual and graphical input using the same tools. There are problems associated with the use of handwriting as an input medium, however, and in this section we shall consider these. We will first look at the mechanisms for capturing handwritten information, and then look at the problems of interpreting it.
Gesture is a component of human–computer interaction that has become the subject of attention in multi-modal systems. Being able to control the computer with certain movements of the hand would be advantageous in many situations where there is no possibility of typing, or when other senses are fully occupied. It could also support communication for people who have hearing loss, if signing could be ‘translated’ into speech or vice versa. But, like speech, gesture is user dependent, subject to variation and co-articulation.
Designing Interfaces for diversity
Employers and manufacturers of computing equipment have not only a moral responsibility to provide accessible products, but often also a legal responsibility. In many countries, legislation now demands that the workplace must be designed to be accessible or at least adaptable to all — the design of software and hardware should not unnecessarily restrict the job prospects of people with disabilities.
We have considered how people differ along a range of sensory, physical and cognitive abilities. However, there are other areas of diversity that impact upon the way we design interfaces. One of these is age. In particular, older people and children have specific needs when it comes to interactive technology.
Cultural difference is often used synonymously with national differences but this is too simplistic. Whilst there are clearly important national cultural differences, such as those we saw, other factors such as age, gender, race, sexuality, class, religion and political persuasion, may all influence an individual’s response to a system. This is particularly the case when considering websites where often the explicit intention is to design for a particular culture or subculture.