Applying cognitive theory
• We have a lot of models and
concepts now
– What good are they?
• Cognitive theory can be useful
for things other than psychology
– Used in engineering to improve
designs
• Two large fields of interest
– Human Computer Interaction
(HCI)
– Human Factors (cognitive
ergonomics)
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Human Computer Interaction
• Three main aims
– Improve access to computing
devices
– Reduce complexity of using
computing devices
– Reduce likelihood of error in using
computing devices
• This is done in various ways
– Mathematical models of computer
use
– Direct observation of computer
use
– Application of cognitive models
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Example: WIMP vs. CLI
• Before 1970s, computers
controlled by command line
interface (CLI)
• Single line of text input
– Needed to know each command’s
keyword
– Needed to know the syntax for
each command
– Eg. Copy [source filename]
[destination filename]
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Problems With CLI
• People found it hard to use
– Forgot command names
– Would transpose command
parameters
– Novices would be overwhelmed
(‘blank screen’)
• Cognitive analysis
– Many of the problems can be
traced to recall vs. recognition
memory
– Commands and syntax had to be
recalled (quite hard)
– Almost no recall cues are provided
– Can expect even experts to make
mistakes
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Solution: WIMP
• Xerox invented the Windows
Icons Mouse and Pointer
(WIMP) interface
• Very few commands (mouse
buttons), bring up options
– Visual metaphor
– Contextually appropriate commands
are brought up
– Drag & Drop ‘removes’ parameters
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Why WIMP works
• Uses recognition rather than
recall
– Icons show available commands
– Menus give complete list of
available commands
• Visual metaphor removes
abstract syntax
– No longer remember order of
commands or positions in path
trees
– Can ‘see’ where things are, move
them from place to place
• Reduced likelyhood of making
syntax errors
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Mental Models
• How do we understand how the
world works?
– More than simple memory
– Includes expectations of
behaviour
• I throw a ball at my friend, and
she catches it
– How did I know how hard to throw
it?
– How did she know where to stand
to catch it?
• We have an understanding of
the mechanics of the world
– How objects interact, the
relationships between them
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What is a mental model?
• A cognitive structure that
encodes how an aspect of the
world operates
• Includes information about
which object classes interact
with which other classes
• Also includes information about
how objects interact, and how
interactions change properties
• Malleable structures which are
strengthened by successful
application
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Mental model example
The circle is above and to the
right of the square
• We can ask questions about this
situation
– Which object is to the left?
– Which object is at the bottom?
– Would the circle balance on the
square?
• By creating a mental model,
these questions are simple to
answer
– Add in knowledge we already
have
– You can simply ‘see’ the answer
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How we use mental models
• We use mental models to
generate predictions
– Predict where the ball will land
• Expertise is generally
associated with mental models
closer to reality
– An expert cricket player
understands ball physics better
– But mental models are always
unconscious (‘knowing’ doesn’t
help)
• Mental models are not based on
accurate physics
– Can lead to incorrect predictions
– Based on experience, etc
– Change as they are used
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Expanding mental models
• HCI researchers have expanded
the idea
– Includes a user’s understanding of
the workings of a computing
device
– Expectations of menu structures,
where files are stored, etc.
• In HCI understanding user’s
mental models is important
– Understand how learning a
system works
– Reduce stress/workload by
supporting user’s mental models
– Tailor systems to fit how users
perceive the system
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Mental models and userinterfaces
• Any interface requires a mental
model to use
– What to expect when typing,
clicking, etc
– How to interpret the
consequences of actions (e.g. link
new window with clicking of the
icon)
• Mental models are important
when interface has little
feedback
– Difficult to recognize results
– Few cues to evaluate the new
state of the system
– Particular problem with
impoverished devices
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Impoverished devices
• Small screen
– Little space for
feedback
– User will have
to ‘remember’
what state the
device is in
• Few input points
(buttons, etc)
– Each button
has many
functions,
depending on
the state of the
device
– User will have
to ‘remember’
buttons
functions in this
state
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Interface modes
• One way to get around small
display problem: use modes
– ‘phone call’ mode
– ‘speaking’ mode
– ‘address book’ mode
– ‘text message’ mode
• In each mode, the
buttons/display take on a new
meaning
– ‘Blue line’ button: in ‘phone call’
mode answers a ring, in ‘speaking’
mode hangs up, in ‘address book’
mode selects the menu option
– Requires fewer buttons
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Modes – cognitive analysis
• Effectively require a mental
model for each mode of the
interface
– Each mode, the input/display has
different meaning
• Can have difficulty selecting the
mental model to use
– Wrong model means errors
– Confusion about interface
behaviour
• Problems can be reduced
– Few modes
– Clearly indicate which modes are
present
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Problems in changing
modes
• The most common modes tend
to dominate
– Well practiced mental models are
more easily activated
– Can lead to confusion
• Problems can arise from ‘mode
confusion’
– Thought you were in one mode,
note the other
– Can be reduced by clearly
indicating modes (eg. Colour
change)
– Difficult in small, monochrome
displays
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Example: Showing mode context
Active mode
Actions under
this mode
Active mode shown
by layout
Sony Ericsson P800
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Navigating modes
• Phones change modes by
menus
– Each menu option set s a new
mode
• Finding your way around a
menu is called navigating the
menu
• Menu design has a large impact
on phone usability
– Bad menu presentation
– Confusing grouping of items
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Bad menus
• Menu encode trees of options
– Based on the grouping of functions and
modes
– People experience menus as lists of
options
Phone Book
Messages
Call Register
Settings
Call Divert
Games
Calculator
Clock
Tones
Search
Service Nos.
Add Entry
Erase
Edit
Assign Tone
Send Entry
Options
Speed Dials
Inbox
Outbox
Write Messages
Picture Messages
Message Settings
Info Service
Voice mailbox no
Nokia 3210 menu
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Bad menus
• Spatial position of the item in the
list becomes a retrieval cue
– ‘its near the top’
– Simple to communicate
– To exploit this, need to show
context on the display
– Avoid ‘circular lists’
Single option;
no spatial context
Several options;
spatial context
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Bad menus
• Context is also required to going back
– Correct errors; find place later
• Deep menus are easy to get lost in
(Nokia limits to 2 levels)
– hard to consider it as a list
– difficult to chunk a ‘tree’
• Context can be displayed on the screen
Full context
(6 down, enter, 5 down)
Partial context
(in words)
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Confusing menus
• Menus group items together
– Based on what?
– Some make sense, some not
– Eg. Nokia 3210 (‘assign tone’ in
Phone Book, not Tones)
• Menu groupings are based on
some structure
– If its not shared with your users,
problem!
– The grouping can become a
mental model if the structure
makes sense (deep processing)
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Confusing menus
• Menu structure confusion can
be overcome
– Memorize how to access functions
– Allow menu customization (not
with phones!)
– ‘flatten’ the tree (can browse more
easily)
• Having no sub-menus can help
– Simple mental model (line)
– Browse each time
• Having no sub menus can
hinder
– No structure to organize
– Forced to browse each function
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Alternative: No menus at all!
• Nokia experimental interface
– No menus; simply type what you want
– Uses a T9 text-prediction to reduce the
keystrokes required
• Uses recall rather than recognition!!
– But not a severe problem
– Number of frequently used functions tiny
(phone book, SMS, missed calls)
• How to overcome weird technical
terms?
– Use multiple phrases for the same
function
– Eg. Address book, Numbers, Phone
Book, My Numbers List, People
– Possibility of adding terms to the
dictionary
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Summary: Using mental models
to make a better phone
• Provide context on the display
– Reduces mental workload
– Allows people to keep track of
where they are in the model
• Structure the information the
way your users understand it
– Support the models they have
– Prevent them from having to
replace current models
• Keep structures simple
– Lists, shallow trees
– Avoid removing ‘spatial’
information
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