§7-Cognitive aspects Flashcards
Why Cognitive Psychology for Interaction Design?
- understand the world view of the user
- to design the interface in a way which is consistent with the world view
EXAMPLES?
List five tools for understanding how humans think
- The Model Human Processor
- Core aspects of cognition
- Memory
- Gestalt psychology
- Human perception
(tool 1) three components of the model human processor
- perceptual
- cognitive
- motor
Describe the perceptual subsystem
- input: senses (visual, auditory, haptic)
- fed into visual image store, audio image store, via perceptual processor
1. information is stored in memory (sensory, working/ST, LTM)
Describe the cognitive subsystem
- output of perceptual subsystem is fed into working memory (STM)
- exchanges between LTM, STM and the cognitive processor
- output from working memory to the motor subsystem
Activities of the cognitive processor
- reasoning,
- skill acquisition
- error feedback
Describe the movement subsystem
- output from cognitive subsystem into motor processor
2. motor processor drives the movement response
Processor cycle times and consequences
- Tperceptual > Tcog, Tmot
- Tperceptual is shorter for more intense stimuli
- Tmotor ~ Tcog
- allows a system designer to predict the time it takes to complete a task
(tool 2) list four core cognitive aspects
- perception and recognition
- memory
- reading, speaking listening,
- problem solving,…, learning
what are the three types of memory, how is info transferred between them
Three types of memory
- sensory buffers
- short term memory
- long term memory
- attention moves info from sensory buffers to STM
- rehearsal moves from STM to LTM
- recall moves info from LTM to STM
Properties of sensory/perceptual memory
- buffers for stimuli, passive (only moved to STM if user pays attention)
- constantly overwritten by new information (kept for ~0.5 s before overwritten)
- either overwritten and lost or passed into a more permanent memory store
What is the role of attention
- passes information from sensory memory to STM
- defined as concentration on one out of a number of competing stimuli
Design implications arising from the properties of sensory memory
- cannot assume that if a person heard or saw a message 5 secs earlier, they will still remember it (may have been overwritten / not received attention)
- keep message displayed until not needed; or make it so that the user can apply the information immediately.
- as focus is directed towards the information, it moves to STM, where it persists for < 10 seconds
Consequences of human short term memory limitations
- rapidly accessible
- transient
- limited capacity of 7±2 chunks
- information subject to interference
- items are lost from memory if not rehearsed
Principle of chunking + examples
- STM can store 7±2 chunks, mainly regardless of how complex those chunks are
~ STM constrained by number of chunks not basic elements (e.g. digits)
Patterns can be useful as aids to memory by imposing chunks
Examples
- long list -> categories : thrashing
- divide up a phone number/registration plate
- divide up menus
Issues about storage of information
- rehearsal to move info from STM to LTM
- total time hypothesis – retention is proportional to rehearsal time
- distribution of practice effect – optimise retention by spreading learning over time (fragmented and repeated rather than massed)
- structure, meaning and familiarity makes information easier to remember (interface metaphors)
Issues about forgetting from LTM
- decay – information is lost but slowly
- interference arises when new information replaces old, old may interfere with new
- selective memory – choose to forget/influence of emotion
Issues about retrieval
- recall – remembering something .e.g password
- recognition occurs when you are presented with the item you are trying to remember e.g. when listing all files in home directory
Example of memory issues in improving a menu interface
text style selector menu
- modify text to be in the style that it is selecting (recall to recognition)
- group items by text alignment, font modification, … (chunking / avoids thrashing)
LTM : context
Context plays a major role in what people see and hear
LTM : mind set
Factors that we know and bring to a situation can have a profound effect on the usability of an interface
e.g. meaning of certain colours, assumptions about the behaviour of interface metaphors
LTM : grouping
If you do not try to add grouping into the interface… the user’s perceptual processes will still try to impose a structure
on the display
- and it might not be the structure you want!
EXAMPLES?
Define Gestalt psychology
- idea: we do not see things in isolation but as parts of a whole
- structured layouts are easier to perceive
- importance of context in aiding perception
List the six gestalt laws
- figure ground relationship
- proximity
- similarity
- symmetry
- continuity
- closure
Gestalt: figure ground relationship
we group elements either as figures or ground
affects legibility – contrast of black text upon a dark background
Gestalt: proximity
we group by distance
consistency of fonts – suggests that similar actions are performed by each thing
Gestalt: similarity
we group by type (font/colour/…)
Gestalt: symmetry
we group by meaning (or distinguish by meaning)
menus on opposite sides of screen
Gestalt: continuity
we group by alignment or flow (even if the lines were drawn in a way which might suggest an alternative grouping)
Gestalt: closure
we perceive things which are not (completely) there
e.g. present an icon – of a person, as a semicircle and a circle
removes irrelevant information – provides an abstraction – doesn’t distract from what the purpose of the button is
(tool 5) visual perception – what are its key properties
visual perception is active (more likely to be transferred into STM)
What is selective attention and perceptual expectancy
selective attention – ability to ignore the irrelevant
perceptual expectancy – seeing what we expect to see
Issues related to visual perception involved in reading
Stages
- perception of the visual pattern of a word – cues are important, removed by e.g. capitalisation (but that may force users to slow down, so may therefore be useful for highly important messages).
- decoding wrt internal representation
Issues related to visual perception involved regarding expectation
What we expect to see affects what we perceive reality to be
- e.g. paris in the
the spring
Issues related to visual perception related to colour
perception of an object is determined by the physical context of the object
list of types of colour schemes
- Monochromatic : based on different tones of same colour
- Analogous: based on colours that are adjacent to each other on the colour wheel
- Complementary: based on colours that are on opposite sides of the colour wheel
- Triadic: based on three colours equally spaced around the colour wheel
Four key consequences of cognitive aspects for interaction design
- Users see what they expect to see .: be consistent, exploit prior knowledge
- Users have difficulty focussing on more than one activity at a time: group similar things together, give prominence to important items; reduce thrashing
- Structured layouts are easier to perceive: use the Gestalt laws
- It is easier to recognise than to recall – put the knowledge that the user needs in the user interface rather than forcing them to rely on remembered knowledge – less burden on STM and faster (avoid need for recall from LTM)
