INTERACTION D ESIGN
1 Understanding Users: Part I O VERVIEW
What cognition is.
Experiential vs. Reflexive Cognition
Implications to Design
Core Human Cognitive Processes
2 W HAT GOES IN MHIND
3 E XPERIENTIAL VS . REFLECTIVE
Perceive, act and react to events around us
Drive a car, read a book, have a conversation.
Involves thinking, comparing, decision
Designing, Learning, Writing a book
Require different types of interface
Another view: 4
Automatic vs. Controlled A UTOMATIC VS . CONTROLLED C OGNITIVE
Things that we do without thinking about
Mostly sensory-motor tasks:
Driving, Cycling, Typing etc.
Fast, require minimal attention, unavailable
Not affected by limited capacity of brain and
don’t require attention.
i.e. don’t occupy brain capacity
Cannot change easily once learned. 5 AUTOMATIC VS . CONTROLLED C OGNITIVE
Non-automatic – need thinking.
E.g. mental arithmetic.
Require attention and conscious
Can change relatively easily
compared to automatic ones.
6 A UTOMATIC VS . CONTROLLED : MPLICATION
TO D ESIGN
Goal 1: use of the interface should
capitalize on automatic processes, so that
users conscious thinking focuses on the
actual goal they are trying to achieve.
E.g. their novel rather than how to type it in.
Goal 2: automatic processes are difficult to
unlearn, thus once established should
better stay as they are.
7 CORE C OGNITIVEA SPECTS
Perception and recognition
Reading, speaking and listening
Problem-solving, planning reasoning and
decision making, learning
Most relevant to interaction design are
the first three.
8 P ERCEPTION
How information is acquired from the world and is transformed into
Theories of perception:
Gestalt theory (a bit dated):
Based on the idea that groups of stimuli lead to new things that are distinct from the sum
of their parts, i.e. have distinct Gestaltqualität(form-quality).
Humans have a tenancy to organize stimuli in a certain manner during perceiving.
Whenever possible, perception tends towards simplicity, symmetry and wholeness, the
Prägnanz (= clear-gut, succinct, in modern German).
Famous for their stunning examples (e.g. illusions) to challenge our perception habits.
Our view of the world is constructed both from information in the environment and from
preciously stored knowledge.
We don’t see just a replica or copy of the world as e.g. a camera.
Visual system constructs a model of the world through transforming, enhancing distorting
and discarding information
No construction but actively try to explore (use) our environment to support our activities.
Affordances important in this theory
9 G ESTALT T HEORY OF P ERCEPTION
Humans have a tenancy to organize stimuli in a certain
manner during perceiving.
The parts construct new distinct wholes that have their own
Gestaltqualität (form-quality) and are independent of the
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Humans also effortlessly distinguish between figures and
E.g. which shape is on top which other shape?
Which is the figure and what is the background?
10 G ESTALT PRINCIPLES
Compelling principles about how humans organize
perceived objects in groups.
11 C ONSTRUCTIVIST T HEORY
What do you see?
Could you see it immediately? 12
Now that you saw it can you “stop” seeing it?
Something (the context? a hint?) seems to lie between the stimuli and your C ONSTRUCTIVIST T HEORY
Constructivists claim that perception is more than
just direct registration of sensations.
The end result of perception is constructed in our
in-part through the observed stimulae and
in-part through an internal inference processes.
This was necessary to explain phenomena
otherwise impossible to explain
e.g. perception of depth and size constancy
13 T HE “H YPOTHESIS T HEORY ”
Richard Gregory’s hypothesis theory:
Based on stimuli we receive, we build hypotheses about the
world around us.
Gregory’s important observations:
Perception allows behavior that fits to object characteristics
that are not sensed.
E.g. we sit on a chair even if we don’t see its four legs in place.
Perceptions can be ambiguous or paradoxical (see illusions of
Perceptions can extract familiar objects from a complex
Highly unlikely objects tend to be mistaken for likely objects.
Perception may not be based to what is experienced.
Take two identical photos of some, enlarge the eye pupils of one
and ask experimental subject who is more attractive. 14ey will
answer the one with the large pupils – though they will be unable
to notice any difference between the photos. COGNITIVE LLUSIONS
- COMPETING CLASSIFICATIONS OOBJECTS
15 E COLOGICAL T HEORY OF P ERCEPTION
Theory of direct perception
Led by psychologist J.J. Gibson.
Questioned the constructivist unrealistic lab-oriented and controlled research.
Aimed at avoiding the dualism perceptual experience vs. objective world, but study the
Perception in an evolutionary basis:
It was developed to solve animal problems (find food, avoid predators etc)
It is therefore necessary to think of perception and action in the real world together.
Invariants are properties that remain constant while stimuli change (due to movement)
Affordances are meanings of objects with respect to how they can or cannot be used.
These are perceive directly without mediating inferences the constructivist suggest.
We don’t consider the world moving when we move our eyes.
Experiments showed that our experience of relative sizes of objects…
i.e. the one that we report when asked which object is larger
…may be different from how our body relates to those objects
i.e. is we try to grip the object, our hands seem to perceive different (the correct) size differences. ECOLOGICAL THEORY
Which center circle is larger? 17 E COLOGICAL THEORY
(The circles have equal size actually.)
While your eye mistakes the size of the center balls, your hands will not
if you try to grip them! E COLOGICAL T HEORY
A higher order pattern or structure that is available as a
source of information for the perceiver.
These patterns have properties that stay the same while
stimuli change due to motion.
When an object departs from us with a constant speed, its size
appears to diminish accordingly (= invariant).
Change in the speed by which the size changes, may imply
a) the object accelerated or slowed down, b) the object is
actually changing size.
When we more towards something, textures expand, when we
move away they contract.
A possible one: the ratio of an object’s height to the distance
between it’s base and the horizon is invariant across all
distances from the viewer. ECOLOGICALTHEORY - NVARIANTS
If a/b = a'/b' then A and B are the same
size. A FFORDANCES
“Roughly the affordances of things are what they
furnish, for good or ill, that is, what they afford
the observer.” (Gibson, 1971)
Affordances are the meanings which an
environment has for an animal.
As such they guide behavior – they tell them what is
possible and what is not.
Tables that are stand-on-table or sit-on-table.
Objects that are graspable or throwable
Surfaces that afford supporting.
Substances that afford pouring. 21 P ERCEIVING D EPTH
Perception functions employ a wide variety of cues to
Basic Cues include (but are not at all limited to):
Motion paralax: understand depth by moving.
E.g. when you are traveling by bus or train, cer