Unit - 2
Understanding the Human
- A person’s interaction with the outside world occurs through information being received and sent: input and output.
- In an interaction with computer, user receives information that is output by computer and responds by providing input to computer.
- User’s output become computer’s input and vice versa.
- Input in 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.
- Out of these, first three are most important to HCI.
- Similarly there are number of effectors, including the limbs, fingers, eyes, head and vocal system.
- In the interaction with computer, fingers play primary role, through typing or mouse control.
- Human vision is a highly complex activity but it is the primary source of information for the person.
- Visual perception can be divided into two stages:
Physical reception of stimulus from the outside world
Processing and interpretation of that stimulus
- Vision begins with light and Eye is a mechanism for receiving light and transforming it into electrical energy.
- Vision
- Human vision is a highly complex activity but it is the primary source of information for the person.
- Visual perception can be divided into two stages:
Physical reception of stimulus from the outside world
Processing and interpretation of that stimulus
Vision begins with light and Eye is a mechanism for receiving light and transforming it into electrical energy.
- Light is reflected from objects and their image is focused upside down on the back of the eye
Fig.1 : The Eye (ref 1)
Fig.2 : Visual angle (ref 1)
2. Hearing
- Hearing begins with vibrations in the air or sound waves.
- Our ear receives these vibrations and transmits them through various stages to the auditory nerves.
- Ear comprises of three sections:
- Outer Ear
- Middle Ear
- Inner Ear
- Outer ear is the visible part of the ear and it has two parts:
Pinna - Structure that is attached to the sides of head.
Auditory Canal – Structure in which sound waves are passed to the middle ear.
- 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.
- Sound changes or vibrations in air pressure and has a number of characteristics:
Pitch - frequency of the sound
Low frequency produces a low pitch as well as for high
Loudness is proportional to amplitude of the sound; the frequency remains constant
- The audible range is from 20 Hz to 15 kHz.
- Auditory system performs some filtering of sounds received which allows us to decide the priority i.e. ignoring background noise and concentrating on important information.
- Sound conveys notable amount of information.
- It is rarely used in interface design but usually used as warning sounds and notifications.
- Except in multimedia where music, voice commentary and sound effects are included.
3. Touch
- It is less important than sight or hearing.
- It provides vital information about environment, experience of users of virtual reality games.
- Skin contains three types of sensory receptor:
- Thermoreceptors respond to heat and cold
- Nociceptors respond to intense pressure, heat and pain
- Mechanoreceptors respond to pressure, concerned in relation with HCI
- Two kinds of mechanoreceptor which respond to different types of pressure.
- Rapidly adapting mechanoreceptors respond to immediate pressure as the skin is indented and also react more quickly with increased pressure. However, they stop responding if continuous pressure is applied.
- Slowly adapting mechanoreceptors respond to continuously applied pressure.
4. Movement
- Movement time is dependent on the physical characteristics of the subjects like their age and fitness.
- The Reaction time varies as per the sensory channel through which the stimulus is received. A person can react to an audio signal in approx. 150 ms, to a visual signal in approx. 200 ms and to pain in approx. 700 ms.
- However, a combined signal provides the quickest response. Factors such as skill or practice can reduce reaction time,but fatigue can increase it.
- A second measurement of motor skill is accuracy. The accuracy is dependent on the task and the user.
- Speed and accuracy of movement are the two most important considerations in the design of interactive systems in terms of the time taken to move to a particular target on a screen.
- The Fitt’s law is given by,
Movement time = a + b log2(distance/size + 1)
Where a and b are empirically determined constants.
- This affects the type of target we design.
- Users will find it more difficult to manipulate small objects therefore the target should be as large as possible and the distance it is to be moved should be as small as possible.
• Memory games rely on our ability to store and retrieve information.
• This is how our memory system works.
• Our everyday activities rely on memory as well as storing all our factual information, our memory comprises of our knowledge of actions.
Fig.3: Memory types (ref 1)
- Sensory Memory
It acts as a buffer for stimuli received through senses.
It exists for each sensory channel as
- Iconic Memory for Visual Stimuli
- Echoic Memory for Aural Stimuli
- Haptic Memory for Touch
These memories are constantly overwritten by new information coming in on these channels.
Information is passed from sensory memory into short-term memory by attention.
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 and this is due to the limited capacity of our sensory and mental processes.
If we did not attend to the stimuli coming into our senses, we would feel overloaded.
- Short-term memory
It acts as ‘scratch-pad’ for temporary recall of information.
It is used to store information which is only required quickly.
It can be accessed rapidly, in the order of 70 ms.
It also decays rapidly means information can only be held there temporarily in the order of 200 ms and also has limited capacity.
- Long term memory
If short-term memory is our working memory, long-term memory is our main resource.
It stores factual information, experiential knowledge, procedural rules of behavior i.e. everything that we ‘know’.
It differs from short-term memory in number of significant ways:
• Huge capacity
• Relatively slow access time of approx. Tenth of a second
• Forgetting occurs more slowly in long-term memory
Information is placed from working memory through rehearsal
Two types of long-term memory:
- Episodic Memory - Represents our memory of events and experiences in serial form
- Semantic Memory - structured record of facts, concepts and skills that we have acquired
- Humans use information to reason and solve problems and perform activities when there is partial or no information.
- Human thought is conscious and self-aware, and we may or may not identify the processes we use, but we can surely identify the products of these processes i.e our thoughts.
- Thinking requires different amounts of knowledge. Some thinking activities are very direct and the knowledge required is also constrained whereas others require vast knowledge from different domains.
- The two categories of thinking are : reasoning and problem solving.
- Reasoning
- It is the process which uses the knowledge that we have to draw conclusions or infer something new about the domain of interest.
- There are 3 different types of reasoning: deductive, inductive and abductive.
- We use each of them in our day-to-day life, but they differ in many ways.
- Deductive reasoning
It derives the logically necessary conclusion from the given premises.
It is at this point, where truth and validity clash, that human deduction is poorest.
It allows us to take short cuts which make dialog and interaction between people informative but efficient.
- Inductive reasoning
It is generalization from cases to infer information about cases we did not see.
It is a useful process, which is constantly used in learning about our environment.
- Abductive reasoning
It reasons from a fact to the action or state that caused it. Here, we use to derive explanations for the events we observe.
If an event always follows an action, the user infers that the event is caused by the action unless evidence to the contrary is available. If, in fact, the event and the action are unrelated, confusion and even error occurs..
- Problem solving
- It is the process of finding a solution to an unfamiliar task, using the knowledge that we have.
- Human problem solving is the ability to adapt the information with new situations. However, often solutions seem to be original and creative.
- There are a number of views as to how people solve problems.
- The Gestalt view shows that problem solving involves both reuse of knowledge and insight.
- A second theory, proposed by Newell and Simon, was the problem space theory, which shows that the mind is a limited information processor.
Gestalt theory
- Problem solving is both productive and reproductive.
- Reproductive problem solving is based on previous experience, but productive problem solving is based on insight and restructuring of the problem.
- Reproductive problem solving could hinder to find a solution, since a person may ‘fixate’ on the known aspects of the problem and so unable to see the interpretations that might lead to a solution.
Problem space theory
- The problem space comprises of problem states and problem solving generates 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 one state to another.
- One such theory is means–ends analysis. In this, both the states are compared and an operator is chosen to reduce the difference between the two.
- They have been applied to problem solving in well-defined domains, for example for solving puzzles.
- These problems may be unknown but the knowledge that is required to solve them is present in the statement of the problem itself and the expected solution is clear.
- In real-world problems finding the knowledge that is required to solve the problem may be part of the problem itself or specifying the goal may be difficult too.
- Our emotional response to situations affects how we perform.
- For example, positive emotions enable us to think more creatively to solve complex problems whereas negative emotion pushes us into narrow, focused thinking.
- Problem may be easy to solve when we are relaxed but becomes difficult if we are frustrated or afraid.
- In situations of stress, people are unable to cope with complex problem solving or managing difficult interfaces whereas if people are relaxed they will be more forgiving of limitations in the design.
- This doesn’t give an excuse to design bad interfaces.
- It is well said by a psychologist,
“ Common sense says, we lose our fortune, are sorry and weep; we meet a bear, are frightened and run; we are insulted by a rival, are angry and strike. The hypothesis
Here . . . Is that we feel sorry because we cry, angry because we strike, afraid because we
Tremble.”
(W. James, Principles of Psychology, page 449. Henry Holt, New York, 1890.)
- Our physiological processes are too slow for our emotional reactions, and the physiological responses for emotional states are too similar (e.g. Anger and fear), yet they can be easily distinguished.
- Emotion results from a person evaluating physical responses of the whole situation. The same physiological response can result from a range of different situations, the emotion which is felt is based on a cognitive evaluation of the circumstance and will depend on what the person attributes.
- Our body responds biologically to an external stimulus and we interpret in some way as a particular emotion. That biological response is known as affect that changes the way we deal with different situations, and also has an impact on the way we interact with computer systems.
- It suggests that in situations of stress, people are not able to cope with complex problem solving or managing difficult interfaces, whereas if people are relaxed they are more forgiving of limitations in the design.
- If we build interfaces that will promote positive responses (for example by using aesthetics or reward) then they are more likely be successful.
The psychological principles and properties applies to the majority of people.
Although we share processes in common therefore users, are not all the same.
the individual differ in many ways so that we can account for them as far as possible within our designs.
These differences may be like sex, physical capabilities and intellectual capabilities. Others include the effect of stress or fatigue on the user. Still others change with time, such as age.
These differences should be considered in our designs. It is useful for any designer to decide, if there are users within the target group who will be adversely affected.
Extremely, a decision excludes a section of the user population who are visually impaired, unless the design also uses other sensory channels.
Psychology and the design of interactive systems users who are under pressure, feeling ill or distracted by other concerns should not push users to their perceptual or cognitive limits.
- Application of a psychological principle needs understanding of context, both in terms of where it fits in the wider field of psychology details of the actual experiments, the measures used and the subjects involved.
- The designer who acknowledges the relevance of cognitive psychology does not have the background to derive appropriate conclusions.
- The principles and results from research have been distilled in the form of guidelines for design, models that supports design and techniques for evaluating those design.
Guidelines
General design principles and guidelines can be derived from the theories that we have discussed earlier.
Some of them are relatively straightforward and is assisted by the provision of retrieval cues so interfaces should incorporate recognizable cues wherever possible.
Others are more complex and context dependent and many of them are derived from psychological theory.
Models to support design
The psychological theory has led to the development of analytic and predictive models of user behavior.
Some of them include human problem solving, physical activity and others attempt a more comprehensive view of cognition.
Prediction is made as to how a typical computer user would behave in a given situation and others analyze why that behavior occurred.
All are based on cognitive theory.
Techniques for evaluation
In addition to theoretical understanding of the human, psychology also provides a range of empirical techniques which can employed for the evaluation of our designs and systems.
In order to use them effectively we need to understand the scope and benefits of every method.
References:
- Alan Dix (2008). Human Computer Interaction. Pearson Education. ISBN 978-81-317-1703-5.
- Gerard Jounghyun Kim (20 March 2015). Human–Computer Interaction: Fundamentals and Practice. CRC Press. ISBN 978-1-4822-3390-2.
- Ben Shneiderman; Catherine Plaisant; Maxine Cohen; Steven Jacobs (29 August 2013). Designing the User Interface: Strategies for Effective Human-Computer Interaction. Pearson Education Limited. ISBN 978-1-292-03701-1.
- Donald A. Norman (2013). The Design of Everyday Things Basic Books. ISBN 978-0-465-07299-6.
