Human Computer Interaction

1. Human Computer Interaction Lecture 2 CO2702 + CO2751 Lecture 2 - 20011/12

2. are we human or are we.... • Aims • To explore the human as • Input • Output • Processor • To highlight key theories and knowledge for HCI • Understand some general characteristics of humans CO2702 + CO2751 Lecture 2 - 20011/12

3. The Human • Senses • Body • Thinking • Memory CO2702 + CO2751 Lecture 2 - 20011/12

4. The Human as an Input device • Senses • How we make ‘sense’ of the world around us… CO2702 + CO2751 Lecture 2 - 20011/12

5. Each sense has… • A tool – Eye, skin, ear etc • A process – Nerves, electricity etc • Limitations – Pitch, brightness etc • ….. and there is the added complexity of individual differences in sensory perception http://www.hagenstoons.com CO2702 + CO2751 Lecture 2 - 20011/12

6. Capturing Images Sight: = physical reception of stimulus • The eye – • 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 colour vision CO2702 + CO2751 Lecture 2 - 20011/12

7. Interpreting Images (1) • Size and Depth • visual angle indicates how much of view object occupies(relates to size and distance from eye) • visual acuity is ability to perceive detail (limited) • familiar objects perceived as constant size (in spite of changes in visual angle when far away) CO2702 + CO2751 Lecture 2 - 20011/12

8. Interpreting images (2) • Brightness • Subjective reaction to levels of light • Affected by luminance of object (brightness) • Measured by just noticeable difference • Visual acuity (detail) increases with luminance as does flicker • Colour • Made up of hue, intensity, saturation • Cones sensitive to colour wavelengths • Blue acuity is lowest • 8% males and 1% females colour blind CO2702 + CO2751 Lecture 2 - 20011/12

9. Interpreting images (3) • The visual system compensates for: • Movement. • Changes in luminance. • Context is used to resolve ambiguity. • Optical illusions sometimes occur due to over compensation. CO2702 + CO2751 Lecture 2 - 20011/12

10. Optical Illusions the Ponzo illusion the Muller Lyer illusion CO2702 + CO2751 Lecture 2 - 20011/12

11. 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 – sound frequency. • Loudness – amplitude. • Timbre – type or quality. CO2702 + CO2751 Lecture 2 - 20011/12

12. Hearing (cont) • Humans can hear frequencies from 20hz to 20khz. • Less accurate distinguishing high frequencies than low. • Auditory system filters sounds. • Can attend to sounds over background noise. • For example, the cocktail party phenomenon. CO2702 + CO2751 Lecture 2 - 20011/12

13. Touch • Provides important feedback about environment. • May be key sense for someone who is visually impaired. • Stimulus received via receptors in the skin: • Thermo receptors – heat and cold. • Nociceptors – pain. • Mechanoreceptors – pressure. • Some areas more sensitive than others e.g. Fingers. • Kinethesis - awareness of body position. • Affects comfort and performance. CO2702 + CO2751 Lecture 2 - 20011/12

14. Smell and Taste • Tools – nose, tongue • Not much used in computer interfaces but olfactory interfaces using smell are currently being developed… as we will not use these senses we are not discussing them here! CO2702 + CO2751 Lecture 2 - 20011/12

15. The Human in Control • As a machine interacting with computers – humans can use whole body interaction or, more commonly interaction with arms and fingers • Kinect http://www.stelarc.va.com.au CO2702 + CO2751 Lecture 2 - 20011/12

16. The Unpredictable Human • Humans are more than machines – there are aspects that vary. • Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator. http://www.cartoonstock.com CO2702 + CO2751 Lecture 2 - 20011/12

17. Emotion • Various theories of how emotion works • James-Lange: emotion is our interpretation of a physiological response to a stimuli e.g. See axe-wielding maniac, pulse raises, begin to sweat (interpreted as fear) then we run. • Schacter-singer: emotion is the result of our evaluation of our physiological responses, in the light of the whole situation we are in • Emotion clearly involves both cognitive and physical responses to stimuli CO2702 + CO2751 Lecture 2 - 20011/12

18. Emotion (cont.) • The biological response to physical stimuli is called affect • Affect influences how we respond to situations • Positive  creative problem solving • Negative  narrow thinking “Negative affect can make it harder to do even easy tasks; Positive affect can make it easier to do difficult tasks” (Donald Norman) CO2702 + CO2751 Lecture 2 - 20011/12

19. Emotion (cont.) • Implications for interface design • stress will increase the difficulty of problem solving • relaxed users will be more forgiving of shortcomings in design • aesthetically pleasing and rewarding interfaces will increase positive affect • There is a genre of study called affective computing CO2702 + CO2751 Lecture 2 - 20011/12

20. Example from research • ATM machine • Two machines identical in function – number of buttons etc.. • One designed attractively the other not • Attractive one perceived to be easier to use Kurosu, M. & Kashimura, K. (1995) Apparent usability vs. inherent usability: experimental analysis on the determinants of the apparent usability. Denver, Colorado. 292-293. CO2702 + CO2751 Lecture 2 - 20011/12

21. How humans solve problems • Deductive • Inductive • Abductive • reasoning CO2702 + CO2751 Lecture 2 - 20011/12

22. 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. • Logical conclusion not necessarily true: e.g. If it is raining then the ground is dry It is raining Therefore the ground is dry CO2702 + CO2751 Lecture 2 - 20011/12

23. 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. • … But useful! CO2702 + CO2751 Lecture 2 - 20011/12

24. 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 CO2702 + CO2751 Lecture 2 - 20011/12

25. The Human as a Store • Humans have the capacity to remember and retrieve information… this affects the way they use technology http://www.cooperativeindividualism.org CO2702 + CO2751 Lecture 2 - 20011/12

26. Three different ‘stores’ • Sensory buffers: momentary stores for stimuli received by the senses. This information, unless encoded in the short-term memory, is quickly lost. • Short-term memory (or working memory): short-term memory acts as a store for information required fleetingly. • Long-term memory: this forms the main resource for memory. CO2702 + CO2751 Lecture 2 - 20011/12

27. Short Term Memory • An example of this would be recalling a telephone number long enough to write it down. Short-term memory degrades quickly, and has a limited capacity. • Quick access time – 70ms. • Short term storage – 200ms (10 – 20 second decay time). • Limited capacity. • Length of sequence remembered in order = 7 ± 2 (Miller, 1956). chunks of data are similar. recency effect. • Maintained and increased with rehearsal. • Nowadays referred to as ‘Working memory.’ CO2702 + CO2751 Lecture 2 - 20011/12

28. Chunking and STM • Short-term memory holds information that is actively being used (thought about, reasoned with). • A chunk can be thought of as a single object that conveys a larger amount of information (like a chinese ideogram). • Examples of these include words, shapes and colours. However, the information decays in seconds as items are displaced by new items coming in. • Icons are an example of chunked information on a desktop which allows users to distinguish between the various programs available to them. CO2702 + CO2751 Lecture 2 - 20011/12

29. LTM – Networked chunks Here we store everything we ‘know’. Long-term memory is characterised by huge capacity, slow access time and relative accuracy over time. It is organised in an Episodic way. events and experiences in sequential order. And a Semantic way. facts, concepts and skills that we have acquired. • Storage. • Structure, familiarity and concreteness Forgetting. • Decay, interference. • Retrieval. • Recall - reproduced. • Recognition – clue given. CO2702 + CO2751 Lecture 2 - 20011/12

30. Impact on HCI • Understanding the limits of human abilities and the scope of their abilities is essential for good design – we will revisit these aspects later in the course http://www.offthemarkcartoons.com CO2702 + CO2751 Lecture 2 - 20011/12

31. Next Week • More on humans…. CO2702 + CO2751 Lecture 2 - 20011/12