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the human o Information i/o ...

• visual, auditory, haptic, movement o Information stored in memory
• sensory, short-term, long-term o Information processed and applied
• reasoning, problem solving, skill, error o Emotion influences human capabilities o Each person is different Vision Two stages in vision o physical reception of stimulus o processing and interpretation of stimulus The Eye - physical reception o mechanism for receiving light and transforming it into electrical energy o light reflects from objects o images are focused upside-down on retina o retina contains rods for low light vision and cones for colour vision o ganglion cells (brain!) detect pattern and movement Interpreting the signal o 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 Interpreting the signal (cont) o 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 o Colour
• made up of hue, intensity, saturation
• cones sensitive to color wavelengths
• blue acuity is lowest
• 8% males and 1% females colour blind Interpreting the signal (cont) o The visual system compensates for:
• movement
• changes in luminance.if wrong (different from actual system) errors can occur Emotion o Various theories of how emotion works
• James-Lange: emotion is our interpretationof a physiological response to a stimuli
• Cannon: emotion is a psychological response to a stimuli
• 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 Emotion (cont.) o The biological response to physical stimuli is called affect o 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)

Emotion (cont.) o 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 Individual differences o long term
• sex, physical and intellectual abilities o short term
• effect of stress or fatigue o changing
• age Psychologyand the Design of Interactive System o Some direct applications
• e.g. blue acuity is poor blue should not be used for important detail o However, correct application generally requires understanding of context in psychology, and an understandingof particular experimental conditions o A lot of knowledge has been distilled in
• guidelines
• cognitive models
• experimental and analytic evaluation techniques ."LTM - Storage of information o rehearsal
• informationmoves from STM to LTM o total time hypothesis
• amount retained proportional to rehearsal time o distribution of practice effect
• optimized by spreading learning over time o structure, meaning and familiarity - informationeasier to remember LTM - Forgetting decay
• informationis lost gradually but very slowly interference
• new informationreplaces old: retroactive interference
• old may interferewith new: proactive inhibition so may not forget at all memory is selective ... ... affected by emotion - can subconsciously `choose' to forget LTM - retrieval recall
• informationreproduced from memory can be assisted by cues, e.g. categories, imagery recognition
• informationgives knowledge that it has been seen before
• less complex than recall - information is cue Thinking Reasoning :is a means of inferring new informationfromwhatis already known deduction, induction, abduction Problem solving Deductive Reasoning o Deduction:
• derive logically necessary conclusion from given premises.Touch o Provides important feedback about environment.

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
Vision
Two stages in vision
• physical reception of stimulus
• processing and interpretation of stimulus
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
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
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 color wavelengths
– blue acuity is lowest
– 8% males and 1% females colour blind
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
Reading
• Several stages:
– visual patternperceived
– 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
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
Hearing (cont)
• Humans can hear frequencies from 20Hz to
15kHz
• Auditory system filters sounds
– can attend to sounds over background noise.
– for example, the cocktail party phenomenon.
Touch
• Provides important feedback about environment.
• May be key sense for someone who is visually impaired.
• Stimulus received via receptorsin the skin:
– heat and cold

• thermoreceptors nociceptors


• mechanoreceptors
  -pain
  – pressure
  (some instant, some continuous)
  • Some areas more sensitive than others e.g. Fingers.
  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
  Humain Memory
  There are three types of memory function:
  Sensory memories
  Short-term memory or working memory
  Long-term memory Selection of stimuli governed by level of
  .arousal
  sensorymemory
  • Buffers for stimuli received through senses
  – iconic memory: visual stimuli
  – echoic memory: aural stimuli
  – haptic memory: tactile stimuli
  Short-term memory(STM)
  • Scratch-pad for temporary recall
  – rapid access ~ 70ms
  – rapid decay ~ 200ms
  – limited capacity - 7± 2 chunks
  Long-term memory (LTM)
  • Repository for all our knowledge
  – huge or unlimited capacity
  • Two types
  – episodic – serial memory of events
  – semantic – structured memory of facts,concepts, skills
  semantic LTM derived from episodic LTM

Long-term memory (cont.)
• Semantic memory structure
– provides access to information
– representsrelationships between bits of information
– supportsinference
• Model: semantic network
– inheritance– child nodes inherit properties of parent nodes
– relationships between bits of information explicit
– supportsinference through inheritance
-LTM - semantic network

-Models of LTM - Frames
• Information organized in data structures
• Slots in structure instantiated with values for instance of data
• Type–subtyperelationships
Models of LTM - Scripts
Model of stereotypical information required to interpret situation
Script has elements that can be instantiated with values for context

Models of LTM - Production rules
Representation of procedural knowledge.
Condition/action rules if condition is matched then use rule to determine action.

LTM - Storage of information
• rehearsal
– informationmoves 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 – informationeasier to remember
LTM - Forgetting
decay
– informationis lost gradually but very slowly
interference
– new informationreplaces old: retroactive interference
– old may interferewith new: proactive
inhibition
so may not forget at all memory is selective …
… affected by emotion – can subconsciously `choose' to forget
LTM - retrieval
recall
– informationreproduced from memory can be assisted by cues, e.g. categories, imagery
recognition
– informationgives knowledge that it has been seen before
– less complex than recall - information is cue
Thinking
Reasoning :is a means of inferring
new informationfromwhatis already known
deduction, induction, abduction
Problem solving
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

Deduction(cont.)
• When truth and logical validity clash …
e.g. Some people are babies
Some babies cry
Correct?
Inference - Some people cry

Inductive Reasoning
• Induction:
– generalize from cases seen to cases e.g. unseen
all elephants we have seen have trunks
therefore all elephants have trunks.
• Unreliable:
– can only prove false not true … but useful!
• Humans not good at using negative evidence
e.g. Wason's cards.
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
Problem solving
• Process of finding solution to unfamiliar task using knowledge.
• Several theories.
Gestalt •
– problem solving both productive and reproductive
– productive draws on insight and restructuring of problem
– attractive but not enough evidence to explain `insight' etc.
– move away from behaviourism and led towards information processing theories
Problem solving (cont.)
• Problem space theory
– problem space comprises problem states
– problem solvinginvolves generating states usinglegal
• operators
– heuristics may be employedto select operators
• e.g. means-ends analysis
• – operates within humaninformation processing system
• e.g. STM limits etc.
• – largely applied to problem solvingin well-defined areas
• e.g. puzzles rather than knowledge intensiveareas
Problem solving (cont.)
• Analogy
– analogical mapping:
• novel problems in new domain?
• use knowledge of similar problem from similar domain
– analogical mapping difficult if domains are semantically different
• Skill acquisition
– skilled activity characterized by chunking
• lot of information is chunked to optimize STM
– conceptual rather than superficial grouping of problems
– information is structured more effectively
Errors and mental models
Types of error
• 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
  – James-Lange: emotion is our interpretationof a physiological response to a stimuli
  – Cannon: emotion is a psychological response to a stimuli
  – 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
  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)

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
Individual differences
• long term
– sex, physical and intellectual abilities
• short term
– effect of stress or fatigue
• changing
– age
Psychologyand the Design of Interactive System
• Some direct applications
– e.g. blue acuity is poor
blue should not be used for important detail
• However, correct application generally requires understanding of context in psychology, and an understandingof particular experimental conditions
• A lot of knowledge has been distilled in
– guidelines
– cognitive models
– experimental and analytic evaluation techniques ."