Optical Illusions 4/5. Optical Illusions 2/5. Optical Illusions 5/5 Optical Illusions 1/5. Reading. Reading. Fang Chen Spring 2004

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1 Optical Illusions 2/5 Optical Illusions 4/5 the Ponzo illusion the Muller Lyer illusion Optical Illusions 5/5 Optical Illusions 1/5 Mauritz Cornelis Escher Dutch Graphical designer World s first Virtual Reality (VR) Artist 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 and color is important to recognition Negative contrast improves reading from computer screen Reading 1

2 The ear 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 3D-audio Interaural time difference, ITD Interaural intensity difference, IID Confusion Touch Sound source? Cone of confusion Provides important feedback about environment. May be key sense for someone who is visually impaired. Stimulus received via receptors in the skin: thermoreceptors heat and cold nociceptors pain mechanoreceptors pressure (some instant, some continuous) Some areas more sensitive than others e.g. fingers. Kinethesis - awareness of body position affects comfort and performance. 2

3 Movement Time taken to respond to stimulus: reaction time + movement time Movement time dependent on age, fitness etc. Reaction time - dependent on stimulus type: visual ~ 200ms auditory ~ 150 ms pain ~ 700ms Fitts law Fitts' Law describes the time taken to hit a screen target: Mt = a + b log 2 (D/S + 1) where: a and b are empirically determined constants Mt is movement time D is Distance S is Size of target The time taken to hit a target is a function of the size of the target and the distance that has to be moved. memory Buffers from stimuli received through senses Working memory (short term) small capacity (7 ± 2 chunks ) rapid access (~ 70ms) & decay (~200 ms) pass to LTM after a few seconds Long-term memory huge (if not unlimited ) slower access time (~100 ms) w/ little decay Stage Theory Image Store decay Working decay, displacement maintenance rehearsal Long Term decay? interference? chunking / elaboration Long-term memory (LTM) Repository for all our knowledge slow access ~ 1/10 second slow decay, if any huge or unlimited capacity Two types episodic serial memory of events semantic structured memory of facts,concepts, skills semantic LTM derived from episodic LTM LTM - Storage of information rehearsal information moves from STM to LTM total time hypothesis amount retained proportional to rehearsal time distribution of practice effect optimized by spreading learning over time structure, meaning and familiarity information easier to remember 3

4 LTM - retrieval recall information reproduced from memory can be assisted by cues, e.g. categories, imagery recognition information gives knowledge that it has been seen before less complex than recall - information is cue LTM - Forgetting decay information is lost gradually but very slowly interference new information replaces old: retroactive interference old may interfere with new: proactive inhibition so may not forget at all memory is selective affected by emotion can subconsciously `choose' to forget Recognition over Recall Recall info reproduced from memory Recognition presentation of info provides knowledge that info has been seen before easier because of cues to retrieval Reading, speaking, and listening Written language is permanent while listening is transient Reading can be quicker than speaking or listening Listenng requires less cognitive effort Written language is grammatical Speaking has redundant information Table 2-2. The differences between speech perception and reading text Reading the test Each word can be seen as a whole Less ambiguous The text can be continuously available There is no so many redundant information behind the word itself Be accessible only in the focus visual area Listening to speech Spoken word is spread out in time More ambiguous and unclear signal Higher memory demand, the information is transient, a word is heard and then it ends. Contain numerous hints, such as pitch, intonation, stress, timing, to sentence structure and meaning. Can take input from any direction Reasoning Thinking deduction, induction, abduction Problem solving 4

5 Wason's cards 7 E 4 K If a card has a vowel on one side it has an even number on the other Is this true? Problem solving Process of finding solution to unfamiliar task using knowledge. Several theories. Gestalt Problem space theory Analogy Skill acquisition How many cards do you need to turn over to find out?. and which cards? Mental models People use mental model to make inferences about how to carry out tasks when using the interactive products. It is used to fathom what to do when something unexpected happens with a system and when encountering unfamiliar systems. Engineers mental model and users mental model is different. Types of error Errors slips right intention, but failed to do it right causes: poor physical skill,inattention etc. change to aspect of skilled behaviour can cause slip mistakes wrong intention cause: incorrect understanding humans create mental models to explain behaviour. if wrong (different from actual system) errors can occur Emotion Various theories of how emotion works Emotion clearly involves both cognitive and physical responses to stimuli The biological response to physical stimuli is called affect Affect influences how we respond to situations Implication for interface design How emotions are manifested/measured Physiological respones Heartrate Respiration Skin responsure Blood pressure Questionnaire Facial expression Voice Brain activity Gestures and actions Scott Brave and Cliff Nass: Emotion in Human-Computer Interaction 5

6 Information processing store Perception Long-Term Attention Decision Making Thought working Response Activation Response Execution Feedback Output Attention in perception and display space (1) Selective attention Visual sampling Pursuit eye follows a target moving at a constant speed across the visual field Saccadic jumped view Location Supervisory Target search Optimality of selective attention Select the relevant stimuli to attend at the appropriate times Attention in perception and display space (2) Paralle processing and divided attention Several items within the view field might be processed together Focus attention Broadbent s Filter theory Teeisman s Attenuation theory Deutsch & Deutsch Late filter model Input Input Input register register register Selective filter Attenuation control Perceptual processes Limited capacity Perceptual processes Perceptual processes Selective filter Short-term memory Short-term memory Short-term memory Different bottleneck theories Goal and information presentation If we know exactly what we want to find out, we try to match this with the information that is available The way information is displayed can also greatly influence how easy or difficult it is to attend to appropriate piece of information Individual differences long term sex, physical and intellectual abilities short term effect of stress or fatigue changing age attention Ask yourself: will design decision exclude section of user population? 6