Week 3 - HCI Concepts.pdf

Introduction to Human Computer Interaction SWE234: Human Computer Interaction The Human ©PRISCILLA OLAWALE (MSC) Spring 2024 The Human Information i/o … ◦ visual, auditory, haptic, movement Information stored in m...

Introduction to Human Computer Interaction SWE234: Human Computer Interaction The Human ©PRISCILLA OLAWALE (MSC) Spring 2024 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 ©PRISCILLA OLAWALE (MSC)-SPRING2024 2 Vision Two stages in vision physical reception of stimulus processing and interpretation of stimulus ©PRISCILLA OLAWALE (MSC)-SPRING2024 3 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 colour vision ganglion cells (brain!) detect pattern and movement ©PRISCILLA OLAWALE (MSC)-SPRING2024 4 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 ability to perceive detail (limited) ◦ familiar objects perceived as constant size (in spite of changes in visual angle when far away) ◦ cues like overlapping help perception of size and depth ©PRISCILLA OLAWALE (MSC)-SPRING2024 5 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 Colour ◦ made up of hue, intensity, saturation ◦ cones sensitive to colour wavelengths ◦ blue acuity is lowest ◦ 8% males and 1% females colour blind ©PRISCILLA OLAWALE (MSC)-SPRING2024 6 Interpreting the signal (cont) The visual system compensates for: ◦ movement ◦ changes in luminance. Context is used to resolve ambiguity Optical illusions sometimes occur due to over compensation ©PRISCILLA OLAWALE (MSC)-SPRING2024 7 Optical Illusions the Ponzo illusion the Muller Lyer illusion ©PRISCILLA OLAWALE (MSC)-SPRING2024 8 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 ©PRISCILLA OLAWALE (MSC)-SPRING2024 9 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 ©PRISCILLA OLAWALE (MSC)-SPRING2024 10 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. ◦ for example, the cocktail party phenomenon. ©PRISCILLA OLAWALE (MSC)-SPRING2024 11 Touch 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. ©PRISCILLA OLAWALE (MSC)-SPRING2024 12 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 Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator. ©PRISCILLA OLAWALE (MSC)-SPRING2024 13 Movement (cont) Fitts' Law describes the time taken to hit a screen target: Mt = a + b log2(D/S + 1) where: a and b are empirically determined constants Mt is movement time D is Distance S is Size of target targets as large as possible distances as small as possible ©PRISCILLA OLAWALE (MSC)-SPRING2024 14