Is COM objectoriented

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Designing user interfaces
Lecture 2 Human aspects of HCI
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How does this topic relate to the course?
Source ACM SIGCHI, 1992
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Human information processing

• Information is
• Received via input channels (senses)
• Responses given via output channels (motor
  behaviours)
• Stored in memory
• Processed and applied

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Input and output

• Senses
• Sight
• Hearing
• Touch
• Taste
• Smell

• Effectors
• Eyes
• Vocal system
• Fingers
• Limbs
• Head

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The human eye
Source http//www.yorku.ca/eye
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The retina

• Two types of photoreceptors
• Rods
• Cones
• L- receptors
• Long wavelengths (red)
• M- receptors
• Middle wavelengths (green)
• S- receptors
• Short wavelengths (blue)

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Visual angle
Source http//www.yorku.ca/eye
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Visual acuity

• The ability to resolve spatial detail
• Normal visual acuity
• The ability to resolve a spatial pattern
  separated by a visual angle of one minute of arc
• Minimum requirements for interactive work
• 15 minutes of arc (4.3 mm on screen)
• 21 minutes of arc (6.1 mm on screen) in poor
  conditions

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Visual field
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Photometric units

• Luminance is an objective measure of the amount
  of light emitted by an object in Candelas per
  square metre (cd/m2)
• Brightness is a subjective response to light

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Contrast

• Contrast is the relationship between the light
  emitted from an object and light emitted from the
  background
• It is given by
• (Lo - Lb)/Lb
• where Lo is the luminance of the object and Lb is
  the luminance of the background

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Colour

• Hue determined by spectral intensity of light
• Red (long wavelengths)
• Green (medium wavelengths)
• Blue (short wavelengths)
• Intensity (brightness)
• Saturation (amount of whiteness)

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Sound waves
Amplitude
Cycle
Source http//www.asel.udel.edu/speech/tutorials/
acoustics/time_domain.html
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Frequency

• The number of cycles that the wave can complete
  in one second
• Measured in Hertz (1 Hz is 1 cycle per second)
• The human ear can detect sound within the range
  20 Hz to 20,000 Hz
• It is most sensitive to tones at frequencies
  between 200 and 5000 Hz

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Intensity

• Measures the power in a sound in decibels (dB)

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Perceptual attributes (psychoacoustics)

• Pitch
• Psychological attribute of sound associated with
  frequency (scale from low to high)
• Loudness
• Subjective experience of intensity (scale from
  soft to loud)
• Timbre
• Differentiates between two sounds of the same
  pitch, intensity and duration but with different
  wave forms (e.g. musical instruments)

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Haptic perception (touch)

• Skin contains three types of sensory receptor
• Thermoreceptors (heat and cold)
• Nociceptors (intense pressure, heat and pain)
• Mechanoreceptors (pressure)
• Rapidly adapting mechanoreceptors respond to
  changes in stimulation
• Slowly adapting mechanoreceptors respond to
  details

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Haptic perception (kinesthesis)

• Awareness of the position of the body and limbs
• Receptors in the joints
• Rapidly adapting receptors
• Slowly adapting receptors
• Positional receptors

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Motor control

• Depends on the physical characteristics of users
  (e.g. age, health)
• Response time - a person can react to
• An auditory signal in 150 ms
• A visual signal in 200 ms
• Pain in 700 ms

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Accuracy

• Fitts' law for time to move an object on screen
• a b log2(Distance/Size 1)
• where a and b are constants
• How can we reduce this time?
• Increase ...
• Decrease ...
• Speed-accuracy trade-off
• Faster response time versus reduced accuracy

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Multi-store model of memory
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Sensory stores

• Modality-specific. Temporary buffers hold a
  direct representation of sensory information
• Iconic
• Echoic
• Haptic
• Information persistence is limited
• 0.2 sec (iconic)
• 2 sec (echoic)

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Channel from sensory store to STM

• Performs conversion from physical to symbolic
  representation
• Low capacity limits ability to handle all sensory
  input simultaneously
• Attention is the concentration of the mind on one
  out of a number of competing stimuli or thoughts
• Choice is governed by arousal, the level of
  interest or need

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Short-term or working memory

• Characterised by
• Rapid access (70 ms)
• Rapid decay (200 ms)
• Limited capacity (5 - 9 'chunks' of information)
• Chunking can increase STM capacity but leads to
  desire to close current task and so optimise use
  of memory (closure)
• Information is stored in symbolically coded form
• STM is easily overloaded

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Channel from STM to LTM

• Asymmetric (retrieval is fast, but storage is
  slow)
• Storage of information into LTM requires
  rehearsal
• Can be optimised by
• The time spent in learning (total time
  hypothesis)
• The distribution of learning over time
  (distribution of practice effect)
• Meaningfulness (structure, familiarity
  concreteness)

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Long-term memory

• Characterised by
• Relatively slow access (0.1 sec)
• Little decay
• Very large capacity
• There are two types of LTM
• Episodic memory
• Semantic memory
• Information retrieval is associative through
  reconstruction of meaning

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Model Human Processor
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Summary

• Explain how human beings use
• Senses (vision, hearing, touch)
• Motor behaviour (movement)
• Memory (sensory, STM and LTM)
• Describe the Model Human Processor
• Further reading and revision
• Dix et al, Chap 1, pp.11-30, 34
• Mayhew, Chap 2, pp.31-60