TRANSCRIPTS
to the way in which users access information from a system. They also need to consider how they can enter data or give instructions to the system. In doing this, they can make use of a number of different tools and techniques. In fact, as we will see, system designers can adopt a number of methods to ensure high-quality interaction between users and the system. But I suppose the first point to note is that some of these tools are based on the human sciences and others are based on the computer sciences. It’s the first of these that I’m going to focus on now, but I think it’s important to point out that both types of tools are essential for good HCI design.
OK, so to start with let’s take a few moments to consider the role of human sciences. What do we mean when we talk about the human sciences in relation to HCI? Well, research has shown that there are three important areas where human sciences can contribute to HCI. It could be argued that these three aspects also exist for the computer sciences. But as we shall see, they tend to have a different emphasis – I’ll come back in a little while and tell you how they fit together.
The first important point to note here is that the human sciences can be used to build models of the ways in which humans interact with their environment, that is to say how an individual interacts with the world in general and with computers in particular. Its aim is to help system designers in developing the most effective interactions between users and systems. In addition to cognitive psychology, human sciences also draws on social disciplines such as sociology and organizational knowledge. From the point of view of system designers, it is fair to say that it is cognitive psychology which provides tools for detailed approaches to interface design. One example of this is the modelling of human input and output channels, a concept which is similar to input and output in computer systems. Examples of the human input channels are the visual channel which corresponds to the sense of seeing, the aural channel which corresponds to the sense of hearing, and the haptic channel which corresponds to the sense of touch.
Another area that modelling can help with is the type of metaphors which designers can use when designing an interface. One example of a metaphor commonly used is the folder icon to represent a storage area for files. The main aim of the metaphor is to help cut down the amount of time needed for the user to build a mental model of the system objects in their mind. By using tools such as cognitive walkthroughs, modelling can also
help identify likely points of failure for users when they are trying to navigate the system. Increasingly, we find that modelling is used to provide evaluative tools to measure the quality of system interactions from the point of view of the user. It’s true to say that measuring user satisfaction in this way is a very important aspect of modelling. So, as we can see, modelling has been used to develop tools which can help with interface development and the evaluation of the user experience.
The second major point in relation to the role of cognitive psychology in HCI is its contribution to a simple model of how individuals interact with their environment. In terms of understanding how human cognition works, the Model Human Processor, or MHP, identifies three separate systems, namely, perceptual, cognitive and motor systems.
The perceptual system sends information to the cognitive system which is responsible for processing that information to enable people to know and understand their environment. The motor system is responsible for movement. This enables people to interact with the environment in response to their understanding of what is happening, based on the information they receive from the perceptual and cognitive systems. A simple example from everyday life, such as picking up an object, requires many complex interactions within and between the systems. For example, as part of the cognitive system, physical reactions in the eye which detect the colour and shape of objects. These then need to interact with the perceptual system, in order to make sense of what the object represents. In addition, each of these systems has limits to its capacity. George Miller, a cognitive psychologist, argued in his famous 1956 paper that working, or short-term memory is limited to holding between five and nine items of information at any one time. Miller referred to it as ‘the magic number seven plus or minus two’. An understanding of these limits is crucial when designing user-friendly interfaces.
Thirdly, models of human interaction can provide very effective ways of approaching the design of interfaces, and of ensuring their quality. Used in an appropriate way, they can improve the usability of systems and considerably enhance the user experience. Crucially, they can be used to optimize the representation of tasks within the interface because they can help designers to understand how users view the world. By modelling the limitations of the various human systems, it is possible to ensure that the representations of the
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