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Cognitive Framework of HCI
June 23, 2008
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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.
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