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Human Computer Interaction Lecture 2 The Human

Human Computer Interaction Lecture 2 The Human. The Human. Think of human as an information processing system, which contains input/output, stores information and processes information We will therefore consider three components of this system: input-output, memory and processing. The Human.

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Human Computer Interaction Lecture 2 The Human

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  1. Human Computer InteractionLecture 2The Human

  2. The Human • Think of human as an information processing system, which contains input/output, stores information and processes information • We will therefore consider three components of this system: input-output, memory and processing

  3. 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 • Emotion influences human capabilities • Each person is different

  4. Vision Two stages in vision • physical reception of object • processing and interpretation of object

  5. The Eye - physical reception • mechanism for receiving light and transforming it into electrical energy • light is reflected from objects • images are focused upside-down on retina • retina contains rods for low light vision. Rods are responsible for vision in darkness. Approximately 120 million rods.

  6. The Eye - physical reception • Retina also contains cones for colour vision. They are responsible for vision in light. • Cones are concentrated on fovea and rods are concentrated on retina • Blind spot contains neither rods nor cones. • Ganglion cells (brain!) detect pattern and movement

  7. Design Focus • A user concentrating on the middle of the screen cannot be expected to read help text on the bottom line. • So if an error message is to be shown to user, what to do??? • Better use flashing error message

  8. Interpreting the signal • Brightness • subjective reaction to levels of light • affected by luminance of object, which is the amount of light emitted by an object • Contrast is luminance of object and luminance of its background • High display luminance systems are seen to flicker even above 50 Hz.

  9. Interpreting the signal (cont) • Colour • made up of hue, intensity, saturation • Hue is determined by the spectral wavelength of the light • Approximately 150 different hues can be discriminated by the average person • Intensity is the brightness of color • Saturation is the amount of whiteness in color • Cones are sensitive to colour wavelengths. Three types of cones (red, green and blue) • blue acuity is lowest, because only 3-4% of the fovea is occupied by cones which are sensitive to blue light • 8% males and 1% females colour blind

  10. Optical Illusions the Muller Lyer illusion the Ponzo illusion

  11. Reading • Several stages: • visual pattern perceived • decoded using internal representation of language • interpreted using knowledge of syntax and semantics • Reading involves saccades(jerky movements) and fixations • Perception occurs during fixations • Word shape is important to recognition • Negative contrast (dark character on a light screen) improves reading from computer screen

  12. Design Focus • Standard font sizes of 9 to 12 are equally readable, given proportional spacing between lines. • Similarly line lengths of between 2.3 and 5.2 inches (58 and 132 mm) are equally legible. • Nevertheless, reading from a computer screen is slower than from a book. However, this fact can be controlled by careful design of textual interfaces.

  13. Hearing • Sound can convey a remarkable amount of information • Provides information about environment:distances, directions, objects etc. • Physical equipment: • outer ear – protects inner and amplifies sound • middle ear – transmits sound waves as vibrations to innerear • inner ear – chemical transmitters are released and cause impulses in auditory nerve • Sound • pitch – sound frequency • loudness – amplitude • timbre – type or quality

  14. 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. • Sound could be used extensively in interface design to convey information about the system state.

  15. 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 areas more sensitive than others e.g. Fingers and hair

  16. Attention Rehearsal Memory There are three types of memory function: Sensory memories Short-term memory or working memory Long-term memory

  17. Sensory Memory • Buffers for stimuli received through senses • iconic memory: visual stimuli • echoic memory: aural stimuli • haptic memory: touch stimuli • Examples: touch a cup of tea • Information is passed to STM by attention

  18. Short-term memory (STM) • What is the result of 35 * 6??? • Scratch-pad for temporary recall • rapid access • rapid decay

  19. Examples 21234827849320245456 21234 482784 932024 5456 03323583302 0332-35-83-302 ATM Card example

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