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Human computer interaction is the study of how users interact with computers. It is often regarded as the combination of computer science, design, behavioral science and other fields of study. The interaction between the user and computers mainly occurs through user interface provided by the various computers.
The interface provided generally consists of both hardware and software, for example a user may work with a software through various options provided ( like buttons, menus etc..) and another user may operate a machine through a remote control or by any other means of artifacts. In the former case the user is interacting through software and in the latter case through hardware.
Since Human - computer interaction involves both human beings and machines, it is necessary to have supporting knowledge in both humans and computers. From the computers perspective the knowledge is in the form of Operating Systems, Data Bases, Graphics etc. On the human side, communication theory, industrial design disciplines, linguistics, social sciences, cognitive psychology are relevant.
The HCI field is emerging as many people( users ) interact with different machines used in various industry segments, the success of these machines and/or computers highly depends on how people i.e. users are able to interact with these complex machines in a friendly manner. Generally or as a matter of fact a well designed user interface results in highly satisfied users.
The main goal of HCI is to bridge the gap between the Human and computers and design systems which can understand the human tasks hence helping them in achieving what they want
HCI researchers are mainly focus on developing new methods of interacting with computers, designing new hardware and software and developing methods and theories of interaction .
HCI is clearly a multi-disciplinary subject (see Figure 1), and designing an effective interactive system from a single discipline in isolation is almost impossible. Computer scientists, however, are particularly interested in the practicalities of how they can use the principles and methods from each HCI discipline to assist them in designing better systems. Acquiring an understanding of the theory is important, but knowing how to apply the theory to the problem at hand is equally valuable (Dix et al. 2004).
1.1 Importance of interaction design
One of the greatest problem in designing a user interface or any software product is to understand what exactly the user wants from the system or software product. The designer must be able to understand these needs and should map them to mental models or psychological theories to design the system or product.
Mental and Conceptual Models
Mental models represent the psychological or imaginary situations. Generally the human mind makes small - scale models in order to reason, to anticipate an event and derive explanations or reasons from those events. In particular a user interaction with a computer defines how the user thinks in order to do their jobs and how the system assists them in doing their job.
Following are the characteristics of Mental Models
Ø Often unstable and subject to change
Ø Internally inconsistent
Ø Unscientific and may be based on with out any evidence
Ø Can be misinterpreted based on the evidence
Most computer systems represent the implementation model of the system i.e. the logical structure of their programs instead of focusing on user(s) needs and task(s). But the user Mental model of system is different from the implementation model of the system, thus giving rise to a new model known as Conceptual Model (Hudson 2004), If the conceptual model of the system is different from the users Mental Model then the users may find it difficult to use the system
1.2 Types of User Interfaces
The three commonly used types of user interfaces are
Ø Graphical User Interface
Ø Voice User Interface
Ø Multi Modal Interface
Graphical User Interface: Graphical User Interfaces ( in short GUI ) are the most user friendly way of using a computer, as they provide the user with rich set of options to operate the system, alerting the user if he/she is trying to perform an illegal operation, helps user in reverting the changes made earlier.
Voice User Interface: Visual User Interface ( in short VUI ) is what a user interacts through a spoken language. The auditory sensors interact with the user through sound. In VUI speech is the input by user and mostly the output is either speech or non-verbal output by the computer system.
VUI are made up of three components, they are:
Prompts : also know as the messages which are recorded by the system during the interaction
Grammar: The response the user can make for each prompt by the system
Dialog Logic: Determines an action the system can make according to the user response given for the prompt
Multi - Modal Interface: These interfaces are designed to address the problems faced in purely auditory and purely visual interfaces by providing more user friendly human - computer interaction . The Multi - Modal interactive system uses multiple human communication channels to operate the computer. These communication channels translate to a computers input and output devices. A genuine multi-modal system relies on simultaneous use of multiple communication channels for both input and output, which more closely resembles the way in which humans process information (Dix et al. 2004)
2 Design Principles and Theories
One of the major goals of HCI is to make system more receptive to user needs. To achieve this HCI researchers design innovative ways of interacting with computers. Whether designing a new user interface or evaluating an existing user interface, several principles are to be followed. They are:
Ø Focus on user(s) and task(s): Primarily one needs to estimate the number of users required to execute a task. Besides, identify the tasks the user needs to perform and how these tasks are carried out by the users.
Ø Empirical Measurement: Test the interface with real users who carry out their job on day to day basis. Take note on time taken by each user to carry out their daily task with the interface. The results may vary depending on the performance of user(s).
Ø Iterative Design : after recording the empirical measurements follow these steps to design steps
1. Design the user interface
3. Analyze the results
2.1 Shneiderman's Principles of Human - Computer Interface Design:
The eight golden rules of Human - Computer Interface Design are:
ü Similar situations should have same sequences of actions
ü Terminology used in error messages, prompts and alerts should be consistent
ü Color, capitalization, font and layout should be consistent.
2. Enable Frequent Use of shortcut:
ü To increase the interactivity use macros, special short cut keys and hidden commands
3. Give Informative Feedback:
ü For each and every action performed by user, the system should provide a prompt feedback. For e.g. seeking confirmation from user before deleting a file etc.
4. Design Dialogsd to yield closure:
ü Sequence of actions should be organized as groups starting from begin, middle and end. The informative feedback at the end of group of actions informs the user that the action has completed successfully.
5. Offer error prevention and simple error handling:
ü Prevent users in making serious errors when designing a form
ü If users make any error, instructions should be made to detect the error and simple, constructive instructions should be written to recover from the error
6. Permit easy reversal of actions
7. Support internal locus of control:
ü Tedious data entries, inability or inefficient in retrieving the necessary information will arise anxiety and dissatisfaction in a user
8 Reduce short Term memory Load:
ü reduce short term memory load by designing screens where options are clearly visible, or using pull-down menus and icons
2.2 Theories of HCI
2.3 Cognitive Psychology:
It is the study of how people think and learn. The goal of cognitive psychology is to understand how people think, learn, acquire knowledge. Cognitive Psychology is one of the major contributors to HCI research by providing and applying psychological principles that help and predict how human performance.
Information Processing Model:
This model is proposed by Lindsay & Norman (1977), depicts human beings as information processors. This model shows various stages of how information is processed by human beings. These stages are encoding, comparison, response selection and response execution.
2.4 Hackers Action Theory
This theory explains the consequences, determinants and processes of work behavior. The main components of action theory are:
Ø Acts : motivated and regulated by intentions
Ø Actions: These are the smallest unit of cognitive process and sensory-motor process which are directed through goals.
Ø Operations: actions that have no independent goals
To achieve a agoal users change, alter and vary the actions. Rasmussen model of Cognitive Regulation (Rasmussen, 1982, 1983, 1986 ) which supports a Action Theory provides details of various information process that occur that three - levels of action selection.
Rasmussen model of Cognitive Regulation is highly important to HCI as it observes and categorizes user activity and behavior, thus allowing a deeper understanding on how cognitive processes are really occurring, at various levels of interaction with in a user during user/computer interaction.
2.5 Anderson's ACT - R Theory
The Adaptive Character of Thought - Rational( ACT-R) theory describes a cognitive architecture, based on cognitive rules are recognized based on “production rules”. These production rules are if-then pairs using which the humans( or users) acquire knowledge.
The ACT - R theory helps researches in understanding how knowledge is built and is transformed. Similar to ACT - R theory is Norman's stages of action model, which shows various stages on how users learn a new system.
Ø Forming the goal
Ø Forming the intention
Ø Specifying the action
Ø Executing the action
Ø Perceiving the system state
Ø Interpreting the system state
Ø Evaluating the outcome
2.6 GOMS Theory
Developed in 1983 by Stuart Card, Thomas P. Moran and Allen Newell, is a kind of human Information Process Model. GOMS is an acronym for Goals, Operators, Methods and Selection Rules.
Ø Goals : Defines what the user wants to accomplish
Ø Operators : Actions that are performed to reach the goal
Ø Methods : Are the Sequence of operators that accomplish a goal
Ø Selection Rules : As there can be more than one method be available to accomplish a goal, in such a case a user can select a method by applying a selection rule
Though GOMS method is not accurate in human - computer interaction measurement it has its own advantages, using this method on can easily calculate the estimated time of interaction with little efforts and in a short span of time.
A variation of GOMS theory known as Keystroke Level Modeling ( KLM ) is the next GOMS technique introduced by Card, Moran and Newell in their 1983 book. Due to several simple assumptions made in this theory, it is considered as restrictive model of GOMS. The third variant of GOMS model is Natural GOMS Language' or NGOMSL. This technique gives a very strict, but natural, language for building GOMS models.