Principles of good interface design
June 24, 2008
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Natural
A good interface appears to be natural; it should be seen to be the appropriate way of performing a task. It should reflect the users’ task, syntax and semantics and might use the jargon of the user but not IT jargon.
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Consistency
It should reinforce the user’s expectations from any previous interaction with that system or indeed with simulations
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Relevance
The interface should not ask for redundant material. On- screen information should be short and relevant while still making sense. Key press should be reduced to a minimum.
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Supportive
The system should provide adequate information to allow the user to operate and perform the task. Thus there should have:
a. Adequate help facilities
b. Adequate system feedback which should provide information to help the user continue with the task
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Flexibility
The interface should accommodate differences in the user requirements, preferences and level of performance. Users should be able to create their own personalized settings, however, it should not be at the expense of consistency or the organizations’ needs.
HCI: Matching devices with work
June 24, 2008
Depending on the task, any arbitrary chosen property of any input device can contribute an advantage in one situation, but a disadvantage in another. While selecting an input device it will be necessary then to:
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Take into account the particular transportations that would have to be earned out to perform required task.
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Try to set up natural mappings between the ways in which the device can be manipulated, the feedback given by the program and the meaning of the result in terms of the users’ mental model.
Matching devices with users
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input for the disabled
Computers can enable disabled people to communicate with others or undertake employment where this would otherwise be difficult or impossible e.g. eye and head movement input.
These are beneficial if users hands are disabled or occupied. If the computer can determine where the user is looking at any given time it can present various options.
There are two main ways of recording eye mute and converting it into input data:
a) Electrophysiological
These records the movement of the muscles that control the eye. Electrodes have to be secured to the skin to detect muscle movement and is therefore subject to general body muovement.
(ii) Photoelectric reflection
These records movement in reflected light from the eye. A user is required to track an object on screen by moving his eyes to maintain a stable image on the central part of the retina where vision is most concentrated.
Matching Devices with the Environment of use:
A user may be in a situation where standard input devices may not be available or cannot be used. In such situations then you should consider technologies that are appropriate to the environment e.g digitizing pen for field work.
ATTENTION & MEMORY CONSTRAINTS in HCI
June 23, 2008
ATTENTION & MEMORY CONSTRAINTS
Attention means taking possession of the mind in clear and vivid form of one out of what seems several simultaneously possible objects or trains of thought. It requires withdrawal from something in order to deal effectively with others.
Focused attention:
This is the ability to attend to one event from what amounts to a mass of competing stimuli in the environment. The streams of information we choose to attend to, will tend to be relevant to the activities or intentions that we have at that time.
Divided Attention
This is attending to more than one thing at a time. Attention is either voluntary or involuntary.
Voluntary attention:
This is when the salient characteristics of the competing stimuli grab our attention.
Focusing attention at the interface
The manner in which we display our attention has a tremendous bearing on how effectively we can interact with the system. The importance of understanding the phenomenon of attention is useful in:
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Catching the attention of potential users.
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Guiding their attention to the relevant information on the display
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Focusing their attention on what they need to be looking at or listening to on any given stage.
Techniques of focusing attention
Structuring information
One way in which interfaces can be designed to help users find the information they need is to structure the interface so that it is easy to navigate through. This requires:
- Presenting just the right amount of information, neither too much nor too little as in both cases the user will have to spend considerable time scanning either through a clattered screen or numerous screens of information.
- By grouping and ordering data into meaningful parts. This meaningful structuring of information makes it easier to perceive and guide attention readily to the appropriate information.
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Color
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Alerting techniques e.g. reverse video, flashing, pop up screen e.t.c.
In using the various methods it should be noted that :
- Important information which needs immediate attention should always be displayed in a prominent place to catch the user’s eye.
- Less urgent information should be displayed in less prominent but specific areas of the screen so that the user will know where to look when the information is required.
- Information that is not needed very often should not be displayed, but made available on request e.g. the help facility.
Note: The two cognitive processes i.e. perception and memory are considered inter-dependent. In order to attend to something the user needs to be able to perceive it.
Multitasking and Interruption
Multitasking is the ability to carry out a number of tasks during the same period of time by alternating between them.
In the real life environment, interruptions are common occurrences and thus multitasking is inevitable. When an activity is attended to, it is said to be foregrounded while the other activities are momentarily suspended.
While most people show great feasibility in coping with multitasking they are also prone to distractions. On returning to a suspended activity it is possible for them to have forgotten where they were in an activity as a result they may not restart where they left off, but they will commence at a different point of entry.
To cope with this problem people use cognitive aids i.e. external representations that are intended to gain our attention at a time relevant to the tasks that need to be performed.
Relevance of Multitasking to HCI
Ideally systems should be designed to provide information systematically about the status of an activity in terms of what has been done and what correctly needs to be ironed out.
If users are distracted from the activities at hand the system should be able to inform them of where they were in that activity when they return to it.
In addition routine background tasks that are prone to be forgotten especially when users are distracted e.g. saving files should be brought to the users attention by displaying remainder prompts at the interface.
Cognitive Framework of HCI
June 23, 2008
Cognitive Framework of HCI
Cognition refers to the process by which we become acquainted with things i.e how we gain knowledge. This includes understanding, remembering, reasoning, attending, being aware, acquiring skills and creating new ideas.
Human Information Processing
Cognitive psychology characterized human as information processors in that everything that is sensed i.e. touched, hearing, sight, smell and taste was considered to be information which the mind processed.
The basic idea was that information enters and exits the human mind through a series of ordered processing stages
(a) Sensory Store:
(b) Short term memory (working memory)
(c) Permanent Memory
(a) Sensory Type:
This holds information for a very brief period of time. It can be regarded as input buffer, holding a direct representation of sensory information. Only a small fraction of all the information entering the sensory stores is attended to and selected for further processing in the short term stores. The rest is lost by being written over by successive information.
(b) Short-term memory (working memory)
Information reaching the short term memory store is actively processed and may then be transferred into the long term memory store. The capacity to hold information in the short term memory is limited in amount and time.
(c) Long-term memory:
Information entering the long term memory is assumed to be permanent.
Perception and Representation:
These are two classes of theories that have attempted to explain the way we see things
- Constructive theories
- Ecologist theories
Constructive Theory
The theory states that the process of seeing is an active one in which our view of the world is constructed both from the information in the environment and from previously stored knowledge.
In the HCI context, our ability to perceive objects on a screen be they text, graphics, 2D or 3D images is as a result of our prior knowledge and expectations as to what should appear and the image that falls on our eyes.
The context of the other characters in the above statement together with our prior knowledge enables us to interpret the meaning of the statement. Hence when presented with ambiguous stimuli our prior knowledge of the world helps us to make sense of it. The same is true for ambiguous information displayed in our computer screens.
Ecological Theory:
This argues that perception is a direct process in which information is simply detected rather than constructed. The primary concern is understanding what we do when we perceive.
Graphical representation of the interface
Ideally it may seem desirable to present information on the screen that has characteristics similar to the objects we perceive in the environment. The main methods that have been used to represent information at the interface are:
(1) Alphanumeric:
These are highly versatile and the meaning can be self evident, however the location time may be longer than for graphic coding.
(2) Use of Graphics:
They are very effective if the code matches the object or operation being represented.
(3) Colour:
This is attractive and efficient however excessive use can be confusing. It is also of limited value to the color blind.
(4) Brightness:
This is a good way of representing information but it can be fatiguing especially if screen contrast is poor.
(5) Blink:
This is good for getting attention but should be suppressible afterwards.
(6) Reverse Video
(7) Underlining
This is useful but can reduce text legibility.
(8) Others:
(a) Line length
(b) Line width
(c) Object size
(d) Combination code etc
Graphical coding for quantitative data:
Graphical coding provides a powerful way of displaying quantitative data. The main advantage of using graphic representation is that it can be easier to perceive:
(a) The relationship between multi-dimensional data.
(b) The trends in data that are constantly changing.
(c) Defects in patterns of real time data e.g. process control output.
Colour coding
Color coding provides many opportunities for coding and structuring information at the interface as well as making it pleasant and enjoyable to look at. However excessive use of colors can lead to color pollution and this can make it difficult to interpret the interface as well as confuse the user.
The use of color has important implications:
(a) Segmentation:
Color is a very powerful way of dividing a display into separate regions. Segmenting a display for detection and search tasks is very useful, particularly in areas that need to be seen as belonging together should have the same color.
(b) Amount of color:
Too many colors in a display will increase search times, therefore colors should be used conservatively
(c) Tasks demands:
Color is most powerful for search tasks. It also makes things stand out, thus you can use colors to make features prominent e.g. current active files should have a certain color.
Note: According to health statistics, 7% of the male population is color blind i.e. unable to distinguish between various colors, thus forms of coding such as brightness or contrast should be used.
ICONS
These are small pictorial images that are used to represent system objects, application tools such as those for drawing etc. Increasingly icons are being used at the interface for a range of systems because they can reduce the complexity of the system making it easier to use.
When a large number of icons are used in applications it can become problematic distinguishing them. Since it may not be possible to make icons that resemble the different tools e.g. in computer aided design, it would be useful to have additional coding such as color, shape and size on the interface.
Disciplines contributing to HCI
June 23, 2008
The main topics that make us the main disciplines of HCI are
- Use and context
- Human aspects
- Computer capabilities
- Development process
Use and context
All HCI takes place within a social and organizational context. Different kinds of applications are required for different purposes. Care is needed to divide tasks between humans and machines. Those activities that are creative and non routine are given to people. Those that are repetitive and routine are given to machines.
Human Aspects:
The knowledge of human psychological and physiological abilities and their limitations is an important task. This involves knowing about such things as human information processing, language, interaction and communication.
Computer Aspects:
The main issues of consideration of the technology side involves input and output techniques, dialog techniques, computer graphics and so on.
Design & Development Process:
The knowledge and consideration from above should be brought into the design and development of information systems. Tools and techniques are needed to build systems. There should also be evaluation methods to enable designers check that their ideas are what is wanted.
Disciplines contributing to HCI
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Computer Science
The main contribution of computer science is to provide knowledge about the capability of technology and ideas about how this potential can be harnessed. Various kinds of techniques to support software design, development and maintenance have been of concern to computer scientists.
Developments include; high level programming languages e.g. 4th and 5th GL, user interface management systems (UIMS), debugging tools, prototyping tools, re-use and reverse engineering concepts and multimedia technology.
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Cognitive Psychology
This is concerned with understanding human behavior and the mental processes that underlie it. The important areas in HCI design are perception, attention, memory, learning, thinking and problem solving.
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Social and Organization Psychology
This is concerned with studying the nature and causes of human behavior in a social context. The four core concerns of psychology are:
The influence of one individual to another person’s attitudes and behaviour.
- The impact of a group on its member’s attitudes and behavior
- The The impact of a member on the group’s activities.
- The relationship between the structure and activities of different groups.
The role of social and organizational psychology is to inform designers about social and organizational structures and about how the introduction of computers will influence working practices.
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Ergonomics or Human Factors
The purpose of ergonomics is to define and design tools and various artifacts for different work, leisure and domestic environment to suit the capacities and capabilities of users.
The role of ergonomics is to translate information from the above sciences into the context of design. The objective is to maximize operators such as safety, efficiency and reliability of performance to make a task easier and to increase feelings of comfort and satisfaction.
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Linguistics
This is the scientific study of languages. Within HCI understanding the structure i.e. (syntax) and meaning i.e. (semantics) is important in developing natural language interfaces and conventional analysis which has been used to understand how individuals and groups interact with computers in natural environments.
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Artificial Intelligence
This is concerned with the development of intelligent computer programs which simulate different aspects of intelligent human behavior.
In particular the focus has been on presenting knowledge structures that are utilized in human problem solving.
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Philosophy, socializing and anthropology
A major concern of the disciplines has been to consider the implications of the introduction of IT to society
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Engineering and Design
Engineering is an applied science that takes the findings of science and utilizes it in the production of objects. Design contributes skill and knowledge to this process.
Note: HCI is neither the study of humans nor the study of technology but the bridge between these two. Its role is to enhance the quality of interaction between humans and computer systems.
This is achieved through systematically applying knowledge about humans goals, capabilities and limitations with knowledge about computer’s capabilities and limitations.
Human Computer Interaction
June 23, 2008
Human computer interaction is about designing computer systems that supports people so that they can carry out their activities productively and safely.
HCI has a role in the design and development of all kinds of systems ranging from those of air traffic controls and nuclear processing plants where safety is of extreme importance. HCI is an inter- disciplinary field and it is a separate area of study.
NB: Poor HCI can endanger life. For computers to be widely accepted and used effectively they need to be well designed for the needs and capabilities of the people for whom they are intended.
Two key principles that help to create good HCI are:
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Visibility i.e. something one can see
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Affordability
i. Visibility
This means good mapping between the controls and their effects.
ii. Affordability
This refers to the properties of objects i.e. what sorts of operations and functions can be done to a particular object.
HCI is a discipline concerned with the design, evaluation and implementation of interactive information systems for human uses and with the study of major phenomenon surrounding them.
Researchers on HCI were concerned with how the use of computers might enrich the personal lives and work of people. In particular they focused on the capabilities and limitation of human users i.e. understanding peoples’ psychological processes while interacting with computers.
With further research it became clear that other aspects impact on users. For example training users, working practices, management and organizational issues and health hazards are all important factors contributing to the success or failure of using Information systems.
The challenges of HCI:
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How to keep abreast of changes in technology.
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How to ensure that their designs offer good HCI as well as harnessing the potential functionality of the new technology.
The goals of HCI are to develop or improve:
a) Utility or functionality of the system
b) Effectiveness
c) Efficiency
d) Usability i.e. making system easy to learn and use.
It should be noted that providing lots of different kinds of functions is not necessarily the way to ensure good usability. In order to provide computer systems with good usability HCI specialists strive to understand the factors such as psychological, ergonomic, organizational and social factors that determine how people operate and make use of computer technology, and to translate that understanding into development of tools and techniques to help designers ensure that computer systems are suitable for the activities for which people will use them, in order to achieve efficient, effective and safe interaction both in terms of individual HCI and group interactions.
In HCI, the belief is that the people using the computer system should come first. Their needs, capabilities and preferences for performing various activities should form the ways in which systems are designed and implemented.
People should not have to change radically to fit in with the system. The system should be designed to match their requirements.
