Human computer Interface designLecture3.pdf
- 1. Human factors in interaction design
- 2. Many kinds of interaction styles available Command Speech Data-entry Form fill-in Query Graphical Web Pen
- 3. for HumanComputer Interaction understand your materials understand computers limitations, capacities, tools, platforms understand people psychological, social aspects human error and their interaction
- 4. Usability measures 5 human factors central to interface evaluation: Time to learn How long does it take for typical members of the community to learn relevant task? Speed of performance How long does it take to perform relevant benchmarks? Rate of errors by users How many and what kinds of errors are made during benchmark tasks? Retention over time Frequency of use and ease of learning Subjective satisfaction Allow for user feedback via interviews, free-form comments and satisfaction scales
- 5. Differences Between The Designer And Operator
- 6. The human Information i/o visual, auditory, haptic, movement Information stored in memory sensory, short-term, long-term Information processed and applied reasoning, problem solving, skill, error Emotion influences human capabilities Each person is different
- 7. Core cognitive aspects Attention Perception and recognition Memory Reading, speaking and listening Problem-solving, planning, reasoning and decision-making, learning
- 8. Vision Two stages in vision physical reception of stimulus processing and interpretation of stimulus
- 9. The Eye - physical reception mechanism for receiving light and transforming it into electrical energy light reflects from objects images are focused upside-down on retina retina contains rods for low light vision and cones for color vision ganglion cells (brain!) detect pattern and movement
- 10. Interpreting the signal Size and depth visual angle indicates how much of view object occupies (relates to size and distance from eye) visual acuity is the ability to perceive detail (limited) cues like overlapping help perception of size and depth
- 11. Interpreting the signal (cont) Brightness subjective reaction to levels of light affected by luminance of object measured by just noticeable difference visual acuity increases with luminance as does flicker Color made up of hue, intensity, saturation cones sensitive to color wavelengths blue acuity is lowest 8% males and 1% females color blind
- 12. color and 3D both often used very badly! color older monitors limited palette beware color blind! use sparingly to reinforce other information 3D effects good for physical information and some graphs but if over used e.g. text in perspective!! 3D pie charts
- 14. bad use of color over use - without very good reason (e.g. kids site) colour blindness poor use of contrast do adjust your set! adjust your monitor to greys only can you still read your screen?
- 15. Interpreting the signal (cont) The visual system compensates for: movement changes in luminance. Optical illusions sometimes occur due to over compensation
- 16. Reading Several stages: visual pattern perceived decoded using internal representation of language interpreted using knowledge of syntax, semantics, pragmatics Reading involves saccades and fixations Perception occurs during fixations Word shape is important to recognition Negative contrast improves reading from computer screen
- 17. Hearing Provides information about environment: distances, directions, objects etc. Physical apparatus: outer ear protects inner and amplifies sound middle ear transmits sound waves as vibrations to inner ear inner ear chemical transmitters are released and cause impulses in auditory nerve Sound pitch loudness timbre sound frequency amplitude type or quality
- 18. Hearing (cont) Humans can hear frequencies from 20Hz to 15kHz less accurate distinguishing high frequencies than low. Auditory system filters sounds can attend to sounds over background noise.
- 19. Touch Provides important feedback about environment. May be key sense for someone who is visually impaired. Stimulus received via receptors in the skin: thermoreceptors nociceptors heat and cold pain mechanoreceptors pressure (some instant, some continuous) Some areas more sensitive than others e.g. fingers.
- 20. Attention Selecting things to concentrate on from the mass around us, at a point in time Information at the interface should be structured to capture users attention, e.g. use perceptual boundaries (windows), color, video, sound and flashing lights
- 21. Use techniques that make things stand out like color, ordering, spacing, underlining, sequencing and animation Avoid cluttering the interface - follow the google.com example of crisp, simple design Avoid using too much because the software allows it Design implications for attention
- 22. An example of over-use of graphics Our Situation State the bad news Be clear, dont try to obscure the situation
- 23. Perception and recognition How information is acquired from the world and transformed into experiences Obvious implication is to design representations that are readily perceivable, e.g. Text should be legible Icons should be easy to distinguish and read
- 24. Which is easiest to read and why?
- 25. Memory There are three types of memory function: Sensory memories Short-term memory or working memory Long-term memory
- 26. Memory Involves encoding and recalling knowledge and acting Appropriately We dont remember everything - involves filtering and processing Context is important in affecting our memory The rise of the GUI over command-based interfaces Better at remembering images than words The use of icons rather than names
- 27. Short-term memory (STM) Scratch-pad for temporary recall rapid access ~ 70ms rapid decay ~ 200ms limited capacity -7賊2 chunks
- 28. Examples 212348278493202 0121 414 2626 HEC ATR ANU PTH ETR EET
- 29. The problem with the classic 72 George Millers theory of how much information people can remember Peoples immediate memory capacity is very limited Many designers have been led to believe that this is useful finding for interaction design
- 30. What some designers get up to Present only 7 options on a menu Display only 7 icons on a tool bar Have no more than 7 bullets in a list Place only 7 items on a pull down menu Place only 7 tabs on the top of a website page But this is wrong? Why?
- 31. Why? People can scan lists of bullets, tabs, menu items till they see the one they want Sometimes a small number of items is good design
- 32. Long-term memory (LTM) Repository for all our knowledge slow access ~ 1/10 second slow decay, if any huge or unlimited capacity
- 33. Long-term memory (cont.) Semantic memory structure provides access to information represents relationships between bits of information Model: semantic network inheritance child nodes inherit properties of parent nodes
- 34. LTM - semantic network
- 35. LTM - Storage of information rehearsal information moves from STM to LTM distribution of practice effect optimized by spreading learning over time structure, meaning and familiarity information easier to remember
- 36. LTM - Forgetting decay information is lost gradually but very slowly interference new information replaces old: retroactive interference old may interfere with new: proactive inhibition
- 37. LTM - retrieval recall information reproduced from memory can be assisted by cues, e.g. categories, imagery
- 39. Deductive Reasoning Deduction: derive logically necessary conclusion from given premises. e.g. If it is Friday then she will go to work It is Friday Therefore she will go to work.
- 40. Deduction (cont.) When truth and logical validity clash e.g. Some people are babies Some babies cry Inference - Some people cry Correct?
- 41. Inductive Reasoning Induction: generalize from cases seen to cases unseen e.g. all elephants we have seen have trunks therefore all elephants have trunks. Unreliable: can only prove false not true
- 42. Abductive reasoning reasoning from event to cause e.g. Sam drives fast when drunk. If I see Sam driving fast, assume drunk. Unreliable: can lead to false explanations
- 43. Problem solving Process of finding solution to unfamiliar task using knowledge.
- 44. Problem solving (cont.) Problem space theory problem space comprises problem states problem solving involves generating states using legal operators operates within human information processing system e.g. STM limits etc.
- 45. Problem solving (cont.) Analogy analogical mapping: novel problems in new domain? use knowledge of similar problem from similar domain analogical mapping difficult if domains are semantically different
- 46. Errors and mental models Types of error slips right intention, but failed to do it right causes: poor physical skill,inattention etc. mistakes wrong intention cause: incorrect understanding humans create mental models to explain behaviour. if wrong (different from actual system) errors can occur
- 47. Mental models Users develop an understanding of a system through learning & using it Knowledge is often described as a mental model How to use the system (what to do next) What to do with unfamiliar systems or unexpected situations (how the system works)
- 48. Everyday reasoning & mental model (a) You arrive home on a cold winters night to a cold house. How do you get the house to warm up as quickly as possible? Set the thermostat to be at its highest or to the desired temperature? (b) You arrive home starving hungry. You look in the fridge and find all that is left is an uncooked pizza. You have an electric oven. Do you warm it up to 175 degrees first and then put it in (as specified by the instructions) or turn the oven up in higher to try to warm it up quicker?
- 49. Heating up a room or oven that is thermostat-controlled Many people have erroneous mental models (Kempton, 1996) Why? General valve theory, where more is more principle is generalised to different settings (e.g. gas pedal, gas cooker, tap, radio volume) Thermostats based on model of on-off switch model
- 50. Heating up a room or oven that is thermostat-controlled Same is often true for understanding how interactive devices and computers work: e.g. frozen cursor/screen - most people will bash all manner of keys
- 51. External cognition Concerned with explaining how we interact with external representations (e.g. maps, notes, diagrams) What computer-based representations can we develop to help even more?
- 52. Externalizing to reduce memory load Diaries, reminders,calendars, notes, shopping lists, to-do lists - written to remind us of what to do Post-its, piles, marked emails - where placed indicates priority of what to do External representations: Remind us that we need to do something (e.g. to buy something for mothers day) Remind us of what to do (e.g. buy a card) Remind us when to do something (e.g. send a card by a certain date)
- 53. Involving users in the design At the very least, talk to users Its surprising how many designers dont! Contextual Inquiries Interview users in their usage place (e.g., office), during their normal routine (e.g., while working) Used to discover users culture, requirements, expectations, etc.
- 54. Involving users in the design Create prototypes Its hard to comment on something that doesnt yet exist Users are good at giving feedback for something that is even partially built