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Department of Computer Science and Engineering
KPR Institute of Engineering and Technology
B.E – COMPUTER SCIENCE AND ENGINEERING
COURSE MATERIAL
(2022-2023: Even Semester)
PREPARED BY
Dr.M.Siva Sangari AsP/ CSE (Course Coordinator)
Ms.T.Preethi AP/ CSE
Ms. Jency A Jebamani AP/ CSE
U19CSP28 – HUMAN COMPUTER INTERACTION
DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING
U19CSP28 – HUMAN COMPUTER INTERACTION
UNIT I – FOUNDATIONS OF HCI
The Human: I/O channels – Memory – Reasoning and problem solving; The computer: Devices – Memory – processing and networks; Interaction: Models – frameworks – Ergonomics – styles – elements – interactivity- Paradigms. Introduction Human-computer interaction (commonly referred to as HCI) researches the design and use of computer technology, focused on the interfaces between people (users) and computers. Researchers in the field of HCI both observe the ways in which humans interact with computers and design technologies that let humans interact with computers in novel ways. User By "user", we may mean an individual user, a group of users working together. An appreciation of the way people's sensory systems (sight, hearing, touch) relay information is vital. Also, different users form different conceptions or mental models about their interactions and have different ways of learning and keeping knowledge and. In addition, cultural and national differences play a part. Computer When we talk about the computer, we're referring to any technology ranging from desktop computers, to large scale computer systems. For example, if we were discussing the design of a Website, then the Website itself would be referred to as "the computer". Devices such as mobile phones or VCRs can also be considered to be ― computers. Interaction There are obvious differences between humans and machines. In spite of these, HCI attempts to ensure that they both get on with each other and interact successfully. In order to achieve a usable system, you need to apply what you know about humans and computers, and consult with likely users throughout the design process. In real systems, the schedule and the budget are important, and it is vital to find a balance between what would be ideal for the users and what is feasible in reality.
contributions from many disciplines. Some of the main disciplines which have contributed to HCI are: Computer Science Technology Software design, development & maintenance User interface management systems (uims) & user interface development environments (uide) Prototyping tools Graphics Cognitive Psychology information processing capabilities limitations cooperative working performance prediction Social Psychology social & organizational structures Ergonomics/Human Factors hardware design display readability Linguistics natural language interfaces Artificial Intelligence intelligent software Engineering & Design graphic design engineering principles INPUT–OUTPUT CHANNELS A person‘s interaction with the outside world occurs through information being received and sent: input and output. In an interaction with a computer the user receives information that is output by the computer, and responds by providing input to the computer – the user‘s output becomes the computer‘s input and vice versa. For example, sight may be used primarily in receiving information from the computer, but it can also be used to provide information to the computer, for example by fixating on a particular screen point when using an eyegaze system. Input in the human occurs mainly through the senses and output through the motor control of the effectors. There are five major senses: sight, hearing, touch, taste and smell. Of these, the first three are the most important to HCI. Taste and smell do not currently play a significant role in HCI, and it is not clear whether they could be exploited at all in general computer systems, although they could have a role to play in more specialized systems (smells to give warning of malfunction, for example) or in augmented reality systems. Vision, hearing and touch are central. There are a number of effectors, including the limbs, fingers, eyes, head and vocal system. In the interaction with the computer, the fingers play the primary role, through typing or mouse control, with some use of voice, and eye, head and body position.
Imagine using a personal computer (PC) with a mouse and a keyboard. The application you are using has a graphical interface, with menus, icons and windows. In your interaction with this system you receive information primarily by sight, from what appears on the screen. Vision Human vision is a highly complex activity with a range of physical and perceptual limitations. We can roughly divide visual perception into two stages: the physical reception of the stimulus from the outside world, and the processing and interpretation of that stimulus. On the one hand the physical properties of the eye and the visual system mean that there are certain things that cannot be seen by the human; on the other the interpretative capabilities of visual processing allow images to be constructed from incomplete information. We need to understand both stages as both influence what can and cannot be perceived visually by a human being, which in turn directly affects the way that we design computer systems. We will begin by looking at the eye as a physical receptor, and then go on to consider the processing involved in basic vision. The human eye Vision begins with light. The eye is a mechanism for receiving light and transforming it into electrical energy. Light is reflected from objects in the world and their image is focused upside down on the back of the eye. The receptors in the eye transform it into electrical signals which are passed to the brain. The eye has a number of important components. The cornea and lens at the front of the eye focus the light into a sharp image on the back of the eye, the retina. The retina is light sensitive and contains two types of photoreceptor: rods and cones. Rods are highly sensitive to light and therefore allow us to see under a low level of illumination. They are unable to resolve fine detail and are subject to light saturation. This is the reason for the temporary blindness we get when moving from a darkened room into sunlight: the rods have been active and are saturated by the sudden light. The cones do not operate either as they are suppressed by the rods. We are therefore temporarily unable to see at all. There are approximately 120 million rods per eye which are mainly situated towards the edges of the retina. Rods therefore dominate peripheral vision. Cones are the second type of receptor in the eye. They are less sensitive to light than the rods and can therefore tolerate more light. There are three types of cone, each sensitive to a different wavelength of light. This allows color vision. The eye has approximately 6 million cones, mainly concentrated on the fovea, a small area of the retina on which images are fixated. Figure: Human Eye
can be measured using a photometer. Contrast is related to luminance: it is a function of the luminance of an object and the luminance of its background. Perceiving color A third factor that we need to consider is perception of color. Color is usually regarded as being made up of three components: hue, intensity and saturation. Hue is determined by the spectral wavelength of the light. Blues have short wavelengths, greens medium and reds long. Approximately 150 different hues can be discriminated by the average person. Intensity is the brightness of the color, and saturation is the amount of whiteness in the color. By varying these two, we can perceive in the region of 7 million different colors. The capabilities and limitations of visual processing Visual processing involves the transformation and interpretation of a complete image, from the light that is thrown onto the retina. Visual processing compensates for the movement of the image on the retina which occurs as we move around and as the object which we see moves. Although the retinal image is moving, the image that we perceive is stable. Similarly, colour and brightness of objects are perceived as constant, in spite of changes in luminance. This ability to interpret and exploit our expectations can be used to resolve ambiguity. For example, consider the image shown in Figure is an ambiguous shape Now consider Figures below. The context in which the object appears allows our expectations to clearly disambiguate the interpretation of the object, as either a B or a 13. Consider Figure below, which line is longer? Most people when presented with this will say that the top line is longer than the bottom. In fact, the two lines are the same length. This may be due to a false application of the law of size constancy: the top line appears like a concave edge, the bottom like a convex edge.
Reading There are several stages in the reading process. First, the visual pattern of the word on the page is perceived. It is then decoded with reference to an internal representation of language. The final stages of language processing include syntactic and semantic analysis and operate on phrases or sentences. During reading, the eye makes jerky movements called saccades followed by fixations. Perception occurs during the fixation periods, which account for approximately 94% of the time elapsed. The eye moves backwards over the text as well as forwards, in what are known as regressions. If the text is complex there will be more regressions. Adults read approximately 250 words a minute. It is unlikely that words are scanned serially, character by character, since experiments have shown that words can be recognized as quickly as single characters. Instead, familiar words are recognized using word shape. This means that removing the word shape clues (for example, by capitalizing words) is detrimental to reading speed and accuracy. The speed at which text can be read is a measure of its legibility. Experiments have shown that standard font sizes of 9 to 12 points are equally legible, given proportional spacing between lines. Similarly line lengths of between 2.3 and inches (58 and 132 mm) are equally legible. However, there is evidence that reading from a computer screen is slower than from a book. This is thought to be due to a number of factors including a longer line length, fewer words to a page, orientation and the familiarity of the medium of the page. These factors can of course be reduced by careful design of textual interfaces. A negative contrast (dark, characters on a light screen) provides higher luminance and, therefore, increased acuity, than a positive contrast. This will in turn increase legibility. Experimental evidence suggests that in practice negative contrast displays are preferred and result in more accurate performance. Hearing The sense of hearing is often considered secondary to sight, but we tend to underestimate the amount of information that we receive through our ears. Hearing begins with vibrations in the air or sound waves. The ear receives these vibrations and transmits them, through various stages, to the auditory nerves. The ear comprises three sections, commonly known as the Outer ear, middle ear and inner ear. The outer ear is the visible part of the ear. It has two parts: the pinna, which is the structure that is attached to the sides of the head, and the auditory canal, along which sound waves are passed to the middle ear. The outer ear serves two purposes. First, it protects the sensitive middle ear from damage. The auditory canal contains wax which prevents dust, dirt and over-inquisitive insects reaching the middle ear. It also maintains the middle ear at a constant temperature. Secondly, the pinna and auditory canal serve to amplify some sounds. The middle ear is a small cavity connected to the outer ear by the tympanic membrane, or ear drum, and to the inner ear by the cochlea. Within the cavity are the ossicles, the smallest bones in the body. Sound waves pass along the auditory canal and vibrate the ear drum which in turn vibrates the ossicles, which transmit the vibrations to the cochlea, and so into the inner ear. This relay is required because, unlike the air-filled outer and middle ears, the inner ear is filled with a denser cochlean liquid. If passed directly from the air to the liquid, the transmission of the sound waves would be poor. By transmitting those via the ossicles the sound waves are concentrated and amplified.
speed of reaction results in reduced accuracy. This is dependent on the task and the user. In some cases, requiring increased reaction time reduces accuracy. This is the premise behind many arcade and video games where less skilled users fail at levels of play that require faster responses. Speed and accuracy of movement are important considerations in the design of interactive systems, primarily in terms of the time taken to move to a particular target on a screen. The target may be a button, a menu item or an icon, for example. The time taken to hit a target is a function of the size of the target and the distance that has to be moved. This is formalized in Fitts‘ law. There are many variations of this formula, which have varying constants, but they are all very similar. One common form is: Movement time = a + b log2(distance/size + 1) where a and b are empirically determined constants. HUMAN MEMORY Our memory contains our knowledge of actions or procedures. It allows us to repeat actions, to use language, and to use new information received via our senses. It also gives us our sense of identity, by preserving information from our past experiences. Memory is the second part of our model of the human as an information-processing system. Memory is associated with each level of processing. Bearing this in mind, we will consider the way in which memory is structured and the activities that take place within the system. It is generally agreed that there are three types of memory or memory function: sensory buffers, short-term memory or working memory, and long-term memory. There is some disagreement as to whether these are three separate systems or different functions of the same system. It is sufficient to note three separate types of memory. These memories interact, with information being processed and passed between memory stores. Figure: A model of the structure of memory Sensory memory The sensory memories act as buffers for stimuli received through the senses. A sensory memory exists for each sensory channel: iconic memory for visual stimuli, echoic memory for aural stimuli and haptic memory for touch. These memories are constantly overwritten by new information coming in on these channels. The existence of echoic memory is evidenced by our ability to ascertain the direction from which a sound originates. This is due to information being received by both ears. Since this information is received at different times, we must store the stimulus in the meantime. Echoic memory allows brief play-back of information. Information is passed from sensory memory into short-term memory by attention, thereby filtering the stimuli to only those which are of interest at a given time. Attention is the concentration of the mind on one out of a number of competing stimuli or thoughts. It is clear that we are able to focus our attention selectively, choosing to attend to one thing rather than another. This is due to the limited capacity of our sensory and mental processes.
Short-term memory Short-term memory or working memory acts as a scratch-pad for temporary recall of information. It is used to store information which is only required fleetingly. Short-term memory can be accessed rapidly, in the order of 70 ms. It also decays rapidly, meaning that information can only be held there temporarily, in the order of 200 ms. Short-term memory also has a limited capacity. There are two basic methods for measuring memory capacity. The first involves determining the length of a sequence which can be remembered in order. The second allows items to be freely recalled in any order. Figure: Model of short-term memory Long-term memory If short-term memory is our working memory or ‗scratch-pad‘, long-term memory is our main resource. Here we store factual information, experiential knowledge, procedural rules of behavior – in fact, everything that we ‗know‘. It differs from short-term memory in a number of significant ways. First, it has a huge, if not unlimited, capacity. Secondly, it has a relatively slow access time of approximately a tenth of a second. Thirdly, forgetting occurs more slowly in long-term memory, if at all. Long-term memory is intended for the long-term storage of information. Information is placed there from working memory through rehearsal. Unlike working memory there is little decay: long-term recall after minutes is the same as that after hours or days. Long-term memory structure There are two types of long-term memory: episodic memory and semantic memory. Episodic memory represents our memory of events and experiences in a serial form. It is from this memory that we can reconstruct the actual events that took place at a given point in our lives. Semantic memory, on the other hand, is a structured record of facts, concepts and skills that we have acquired. The information in semantic memory is derived from that in our episodic memory.
Reasoning Reasoning is the process by which we use the knowledge we have to draw conclusions or infer something new about the domain of interest. There are a number of different types of reasoning: deductive, inductive and abductive. We use each of these types of reasoning in everyday life, but they differ in significant ways. Deductive reasoning Deductive reasoning derives the logically necessary conclusion from the given premises. For example, If it is Friday then she will go to work It is Friday Therefore she will go to work. Inductive reasoning Induction is generalizing from cases we have seen to infer information about cases we have not seen. Induction is a useful process, which we use constantly in learning about our environment. We can never see all the elephants that have ever lived or will ever live, but we have certain knowledge about elephants which we are prepared to trust for all practical purposes, which has largely been inferred by induction. Even if we saw an elephant without a trunk, we would be unlikely to move from our position that ‗All elephants have trunks‘, since we are better at using positive than negative evidence. Abductive reasoning The third type of reasoning is abduction. Abduction reasons from a fact to the action or state that caused it. This is the method we use to derive explanations for the events we observe. For example, suppose we know that Sam always drives too fast when she has been drinking. If we see Sam driving too fast we may infer that she has been drinking. Of course, this too is unreliable since there may be another reason why she is driving fast: she may have been called to an emergency. Problem solving Human problem solving is characterized by the ability to adapt the information we have to deal with new situations often solutions seem to be original and creative. There are a number of different views of how people solve problems. The Gestalt view that problem solving involves both reuse of knowledge and insight. This has been largely superseded but the questions it was trying to address remain and its influence can be seen in later research. In the 1970s by Newell and Simon, was the problem space theory, which takes the view that the mind is a limited information processor. Gestalt theory Gestalt psychologists were answering the claim, made by behaviorists, that problem solving is a matter of reproducing known responses or trial and error. This explanation was considered by the Gestalt school to be insufficient to account for human problem-solving behavior. Instead, they claimed, problem solving is both productive and reproductive. Reproductive problem solving draws on previous experience as the behaviorists claimed, but productive problem solving involves insight and restructuring of the problem. Indeed,
reproductive problem solving could be a hindrance to finding a solution, since a person may fixate on the known aspects of the problem and so be unable to see novel interpretations that might lead to a solution. Gestalt psychologists backed up their claims with experimental evidence. Problem space theory Newell and Simon proposed that problem solving centers on the problem space. The problem space comprises problem states, and problem solving involves generating these states using legal state transition operators. The problem has an initial state and a goal state and people use the operators to move from the former to the latter. Such problem spaces may be huge, and so heuristics are employed to select appropriate operators to reach the goal. One such heuristic is means–ends analysis. In means–ends analysis the initial state is compared with the goal state and an operator chosen to reduce the difference between the two. Newell and Simon‘s theory, and their General Problem Solver model which is based on it, have largely been applied to problem solving in well-defined domains, for example solving puzzles. These problems may be unfamiliar but the knowledge that is required to solve them is present in the statement of the problem and the expected solution is clear. In real-world problems finding the knowledge required to solve the problem may be part of the problem, or specifying the goal may be difficult. Analogy in problem solving A third element of problem solving is the use of analogy. Similarities between the known domain and the new one are noted and operators from the known domain are transferred to the new one. Skill acquisition All of the problem solving that we have considered so far has concentrated on handling unfamiliar problems. A commonly studied domain is chess playing. It is particularly suitable since it lends itself easily to representation in terms of problem space theory. The initial state is the opening board position; the goal state is one player checkmating the other; operators to move states are legal moves of chess. It is therefore possible to examine skilled behavior within the context of the problem space theory of problem solving. Errors and mental models Human capability for interpreting and manipulating information is quite impressive. Some are trivial, resulting in no more than temporary inconvenience or annoyance. Others may be more serious, requiring substantial effort to correct. THE COMPUTER A typical computer system There is the computer box itself, a keyboard, a mouse and a color screen. The screen layout is shown alongside it. Data have to be entered into and obtained from a system, and there are also many different types of user, each with their own unique requirements.
o digital paper may be usable in the near future. Virtual reality systems and 3D visualization which have special interaction and display devices. Various devices in the physical world: o physical controls and dedicated displays o sound, smell and haptic feedback o sensors for nearly everything including movement, temperature, bio- signs. Paper output and input: the paperless office and the less-paper office: o different types of printers and their characteristics, character styles and fonts o Scanners and optical character recognition. Memory: o Short-term memory: RAM o Long-term memory: magnetic and optical disks o capacity limitations related to document and video storage o Access methods as they limit or help the user Processing: o the effects when systems run too slow or too fast, the myth of the infinitely fast machine o limitations on processing speed o Networks and their impact on system performance. Network Hubs o Switches o Bridges o Routers o Gateways o Network interface cards (NICs), ISDN adapters, and system area network cards o Wireless access points (WAPs) Interaction models Interaction involves at least two participants: the user and the system. The interface must therefore effectively translate between them to allow the interaction to be successful. This translation can fail at a number of points and for a number of reasons. The use of models of interaction can help us to understand exactly what is going on in the interaction and identify the likely root of difficulties. They also provide us with a framework to compare different interaction styles and to consider interaction problems. The terms of interaction The purpose of an interactive system is to aid a user in accomplishing goals from some application domain. A domain defines an area of expertise and knowledge in some real- world activity. Some examples of domains are graphic design, authoring and process control in a factory. A domain consists of concepts that highlight its important aspects. In a graphic design domain, some of the important concepts are geometric shapes, a drawing surface and a drawing utensil. Tasks are operations to manipulate the concepts of a domain. A goal is the desired
output from a performed task. For example, one task within the graphic design domain is the construction of a specific geometric shape with particular attributes on the drawing surface. A related goal would be to produce a solid red triangle centered on the canvas. An intention is a specific action required to meet the goal. The execution–evaluation cycle The interactive cycle can be divided into two major phases: execution and evaluation. These can then be subdivided into further stages, seven in all. The stages in Norman‘s model of interaction are as follows:
- Establishing the goal.
- Forming the intention.
- Specifying the action sequence.
- Executing the action.
- Perceiving the system state.
- Interpreting the system state.
- Evaluating the system state with respect to the goals and intentions. It is liable to be imprecise and therefore needs to be translated into the more specific intention, and the actual actions that will reach the goal, before it can be executed by the user. The user perceives the new state of the system, after execution of the action sequence, and interprets it in terms of his expectations. If the system state reflects the user‘s goal then the computer has done what he wanted and the interaction has been successful; otherwise the user must formulate a new goal and repeat the cycle. Norman uses this model of interaction to demonstrate why some interfaces cause problems to their users. He describes these in terms of the gulfs of execution and the gulfs of evaluation. As we noted earlier, the user and the system do not use the same terms to describe the domain and goals – remember that we called the language of the system the core language and the language of the user the task language. The gulf of execution is the difference between the user‘s formulation of the actions to reach the goal and the actions allowed by the system. If the actions allowed by the system correspond to those intended by the user, the interaction will be effective. The interface should therefore aim to reduce this gulf. The gulf of evaluation is the distance between the physical presentation of the system state and the expectation of the user. If the user can readily evaluate the presentation in terms of his goal, the gulf of evaluation is small. The more effort that is required on the part of the user to interpret the presentation, the less effective the interaction. The interaction framework The interaction framework attempts a more realistic description of interaction by including the system explicitly, and breaks it into four main components. The nodes represent the four major components in an interactive system – the System, the User, the Input and the Output. Each component has its own language. In addition to the User‘s task language and the System‘s core language, which we have already introduced, there are languages for both the Input and Output components. Input and Output together form the Interface.
Presentation and screen design relates to the output branch of the framework. The entire framework can be placed within a social and organizational context that also affects the interaction. Each of these areas has important implications for the design of interactive systems and the performance of the user ERGONOMICS Ergonomics (or human factors) is traditionally the study of the physical characteristics of the interaction: how the controls are designed, the physical environment in which the interaction takes place, and the layout and physical qualities of the screen. A primary focus is on user performance and how the interface enhances or detracts from this. In seeking to evaluate these aspects of the interaction, ergonomics will certainly also touch upon human psychology and system constraints. It is a large and established field, which is closely related to but distinct from HCI, and full coverage would demand a book in its own right. Here we consider a few of the issues addressed by ergonomics as an introduction to the field. We will briefly look at the arrangement of controls and displays, the physical environment, health issues and the use of colour. These are by no means exhaustive and are intended only to give an indication of the types of issues and problems addressed by ergonomics. Arrangement of controls and displays The exact organization that this will suggest will depend on the domain and the application, but possible organizations include the following: Functional controls and displays are organized so that those that are functionally related are placed together; Sequential controls and displays are organized to reflect the order of their use in a typical interaction (this may be especially appropriate in domains where a particular task sequence is enforced, such as aviation); Frequency controls and displays are organized according to how frequently they are used, with the most commonly used controls being the most easily accessible. The physical environment of the interaction Physical issues in the layout and arrangement of the machine interface, ergonomics is concerned with the design of the work environment itself. This will depend largely on the domain and will be more critical in specific control and operational settings than in general computer use. The physical environment in which the system is used may influence how well it is accepted and even the health and safety of its users. It should therefore be considered in all design. The first consideration here is the size of the users. Obviously this is going to vary considerably. All users should be comfortably able to see critical displays. For long periods of use, the user should be seated for comfort and stability. Seating should provide back support. If required to stand, the user should have room to move around in order to reach all the controls. Health issues There are a number of factors that may affect the use of more general computers. Again these are factors in the physical environment that directly affect the quality of the interaction and the user‘s.
Performance: Users should be able to reach all controls comfortably and see all displays. Users should not be expected to stand for long periods and, if sitting, should be provided with back support. If a particular position for a part of the body is to be adopted for long periods (for example, in typing) support should be provided to allow rest. Temperature Extremes of hot or cold will affect performance and, in excessive cases, health. Experimental studies show that performance deteriorates at high or low temperatures, with users being unable to concentrate efficiently. Lighting The lighting level will again depend on the work environment. adequate lighting should be provided to allow users to see the computer screen without discomfort or eyestrain. The light source should also be positioned to avoid glare affecting the display. Noise Excessive noise can be harmful to health, causing the user pain, and in acute cases, loss of hearing. Noise levels should be maintained at a comfortable level in the work environment. This does not necessarily mean no noise at all. Noise can be a stimulus to users and can provide needed confirmation of system activity. Time The time users spend using the system should also be controlled. It has been suggested that excessive use of CRT displays can be harmful to users, particularly pregnant women. The use of color Colors used in the display should be as distinct as possible and the distinction should not be affected by changes in contrast. Blue should not be used to display critical information. If color is used as an indicator it should not be the only cue: additional coding information should be included. The colors used should also correspond to common conventions and user expectations. Red, green and yellow are colors frequently associated with stop, go and standby respectively. Therefore, red may be used to indicate emergency and alarms; green, normal activity; and yellow, standby and auxiliary function. These conventions should not be violated without very good cause. Ergonomics and HCI Ergonomics is a huge area, which is distinct from HCI but sits alongside it. Its contribution to HCI is in determining constraints on the way we design systems and suggesting detailed and specific guidelines and standards. Ergonomic factors are in general well established and understood and are therefore used as the basis for standardizing hardware designs. INTERACTION STYLES Interaction can be seen as a dialog between the computer and the user. The choice of interface style can have a profound effect on the nature of this dialog.
