Lecture 2 CO2702 CO2751 Lecture 2 2001112 1 are we human or are we Aims To explore the human as Input Output Processor To highlight key theories and knowledge for HCI Understand some general characteristics of humans ID: 285473
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Human Computer Interaction
Lecture 2
CO2702 + CO2751 Lecture 2 - 20011/12
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are we human or are we....
AimsTo explore the human as
InputOutputProcessor
To highlight key theories and knowledge for
HCI
Understand some general characteristics of humans
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The HumanSenses
BodyThinkingMemory
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The Human as an Input device
SensesHow we make ‘sense’ of the world around us…
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Each sense has…
A tool – Eye, skin, ear etcA process – Nerves, electricity etcLimitations – Pitch, brightness etc
….. and there is the added complexity of individual differences in sensory perception
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http://www.hagenstoons.comSlide6
Capturing Images
Sight: = physical reception of stimulusThe eye – 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
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Interpreting Images (1)
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)
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Interpreting images (2)
BrightnessSubjective reaction to levels of light
Affected by luminance of object (brightness)Measured by just noticeable difference
Visual acuity
(detail) 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
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Interpreting images (3)
The visual system compensates for:
Movement.
Changes in luminance.
Context is used to resolve ambiguity.
Optical illusions sometimes occur due to over compensation.
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Optical Illusions
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the Ponzo illusion
the Muller Lyer illusionSlide11
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.
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Hearing (cont)
Humans can hear frequencies from 20hz to 20khz.Less accurate distinguishing high frequencies than low.
Auditory system filters sounds.
Can attend to sounds over background noise.
For example, the cocktail party phenomenon.
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Touch
Provides important feedback about environment.
May be key sense
for someone who is visually impaired.
Stimulus received via receptors in the skin:
Thermo receptors – heat and cold.
Nociceptors
– pain.
Mechanoreceptors – pressure
.
Some areas more sensitive than others e.g. Fingers.
Kinethesis
- awareness of body position.
Affects comfort and performance.
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Smell and Taste
Tools – nose, tongueNot much used in computer interfaces but olfactory interfaces
using smell are currently being developed… as we will not use these senses we are not discussing them here!
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The Human in Control
As a machine interacting with computers – humans can use
whole body interaction or, more commonly interaction with arms and fingersKinect
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http://www.stelarc.va.com.auSlide16
The Unpredictable Human
Humans are more than machines – there are aspects that vary.
Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator.
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http://www.cartoonstock.comSlide17
Emotion
Various theories of how emotion works
James-Lange: emotion is our interpretation of a physiological response to a stimuli e.g. See axe-wielding maniac, pulse raises, begin to sweat (interpreted as fear) then we run.
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
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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)
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Emotion (cont.)
Implications for interface designstress will increase the difficulty of problem solving
relaxed users will be more forgiving of shortcomings in designaesthetically pleasing and rewarding interfaces will increase positive affect
There is a genre of study called
affective computing
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Example from research
ATM machineTwo machines identical in function – number of buttons etc..One designed attractively the other not
Attractive one perceived to be easier to use
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Kurosu
, M. &
Kashimura
, K. (1995) Apparent usability vs. inherent usability: experimental analysis on the determinants of the apparent usability. Denver, Colorado. 292-293.Slide21
How humans solve problems
Deductive InductiveAbductive
reasoning
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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
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Inductive Reasoning
Induction:
Generalize from cases seen to cases unseen.E.g.. All elephants we have seen have trunks
therefore all elephants have trunks.
Unreliable:
Can only prove false not true.
… But useful!
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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
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The Human as a Store
Humans have the capacity to remember and retrieve information… this affects the way they use technology
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http://www.cooperativeindividualism.orgSlide26
Three different ‘stores’
Sensory buffers: momentary stores for stimuli received by the senses. This information, unless encoded in the short-term memory, is quickly lost.
Short-term memory (or working memory): short-term memory acts as a store for information required fleetingly. Long-term memory:
this forms the main resource for memory.
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Short Term Memory
An example of this would be recalling a telephone number long enough to write it down. Short-term memory degrades quickly, and has a limited capacity.
Quick access time – 70ms.Short term storage – 200ms (10 – 20 second decay time).
Limited capacity.
Length of sequence remembered in order = 7
± 2 (
Miller, 1956).
chunks of data are similar.
recency
effect.
Maintained and increased with rehearsal.
Nowadays referred to as ‘Working memory.’
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Chunking and STM
Short-term memory holds information that is actively being used (thought about, reasoned with).
A chunk can be thought of as a single object that conveys a larger amount of information (like a chinese ideogram).
Examples of these include words, shapes and
colours
. However, the information decays in seconds as items are displaced by new items coming in.
Icons are an example of chunked information on a desktop which allows users to distinguish between the various programs available to them.
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LTM – Networked chunks
Here we store everything we ‘know’. Long-term memory is characterised by huge capacity, slow access time and relative accuracy over time.
It is organised in an Episodic way.
events and experiences in sequential order.
And a Semantic way.
facts, concepts and skills that we have acquired.
Storage.
Structure, familiarity and concreteness Forgetting.
Decay, interference.
Retrieval.
Recall
- reproduced.
Recognition
– clue given.
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Impact on HCI
Understanding the limits of human abilities and the scope of their abilities is essential for good design – we will revisit these aspects later in the course
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http://www.offthemarkcartoons.comSlide31
Next Week
More on humans….
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