Human Computer Interaction Lecture 2 CO CO2751 Lecture /121

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 CO CO2751 Lecture /122

The Human Senses Body Thinking Memory CO CO2751 Lecture /123

The Human as an Input device Senses How we make ‘sense’ of the world around us… CO CO2751 Lecture /124

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 CO CO2751 Lecture /125

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 CO CO2751 Lecture /126

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) CO CO2751 Lecture /127

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 CO CO2751 Lecture /128

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. CO CO2751 Lecture /129

Optical Illusions CO CO2751 Lecture /1210 the Ponzo illusionthe Muller Lyer illusion

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. CO CO2751 Lecture /1211

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. CO CO2751 Lecture /1212

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. CO CO2751 Lecture /1213

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! CO CO2751 Lecture /1214

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 CO CO2751 Lecture /1215

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. CO CO2751 Lecture /1216

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 CO CO2751 Lecture /1217

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) CO CO2751 Lecture /1218

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 CO CO2751 Lecture /1219

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 CO CO2751 Lecture /1220 Kurosu, M. & Kashimura, K. (1995) Apparent usability vs. inherent usability: experimental analysis on the determinants of the apparent usability. Denver, Colorado

How humans solve problems Deductive Inductive Abductive ◦ reasoning CO CO2751 Lecture /1221

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 CO CO2751 Lecture /1222

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! CO CO2751 Lecture /1223

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 CO CO2751 Lecture /1224

The Human as a Store Humans have the capacity to remember and retrieve information… this affects the way they use technology CO CO2751 Lecture /1225

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. CO CO2751 Lecture /1226

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).Miller, 1956 chunks of data are similar. recency effect. Maintained and increased with rehearsal. Nowadays referred to as ‘Working memory.’ CO CO2751 Lecture /1227

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. CO CO2751 Lecture /1228

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 concretenessForgetting. ◦ Decay, interference. Retrieval. ◦ Recall - reproduced. ◦ Recognition – clue given. CO CO2751 Lecture /1229

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 CO CO2751 Lecture /1230

Next Week More on humans…. CO CO2751 Lecture /1231