human factors & problem solving cognitive psychology 4 computer scientists interactive seminar...
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Human Factors & Problem Solving
Cognitive Psychology4
Computer Scientists
interactive seminar
Lenko GrigorovSchool of Computing, Queen's University
Nov, 2006 4Lenko Grigorov, Queen's University
Human Factors
● Products of research are going to be used by real people. Articles: can they be understood? Software: is it functional and usable?
● HCI: science about the interactions between software systems and people
● Information Visualization: science about representing information in a useful form
● Cognitive Psychology: science about human thinking
Nov, 2006 5Lenko Grigorov, Queen's University
Why study thinking?
● Why is it important to understand human thinking? Artificial Intelligence
● Know what people expect Computer aid
● Most of software falls in this category● Human and computer co-operate on task● Know where human needs assistance
Rule of thumb: Where people excel, computers have trouble ...and vice versa (Dr. Brian Butler,
PSYC, QU)
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Shortest path?
Nov, 2006 7Lenko Grigorov, Queen's University
Shortest path.
Algorithmic solution: 14! = 87 178 291 200 optionsHuman solution: 2 sec.
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Human Cognitive Machine
PerceptionAttention
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Perception
● Humans acquire information from computers mostly through the visual channel
● Visual perception is a very complex process Involves not only physical sensations Brain processes sensations
● Many possible points of failure● Individuals with impaired perceptual processes
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Physical acuity
● One cannot expect acute perception of everything on the screen
● However, good sensitivity to change in the peripheral vision Attention is attracted
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Perceptual assembly
● What & where pathways● Feature extraction and integration (Treisman)
shape
color
locationat
tent
ion
school bus
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Pop-out
● Immediate perception of irregularities
● Doesn't work when irregularities involve more than one feature!
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Gestalt dog
● The whole is more than the sum of its parts.
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Gestalt principles
Proximity
Similarity
Continuity
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Ideas
● How does all this apply to your work?
?
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Memory
● Working memory Perceptual modalities
● Auditory, visual... Control unit
● Management
● Long-term memory Declarative
● Definitions, instructions... Procedural
● How to do things● Can't explain, just perform
Nov, 2006 21Lenko Grigorov, Queen's University
Working vs. Long-term memory
Working memory
● Very fast● Limited
4-5 items● Items can be
chunked and/or encoded “613” is one item:
local area code
Long-term memory
● Slow Both to encode and
retrieve information● Unlimited (in
practice)● Can't be used
directly
Nov, 2006 22Lenko Grigorov, Queen's University
Expert memory
● How do people cope with a complex world with so little memory?
● Experts have long-term working memory... Fast and unlimited Information arranged in associative structures
which improve access and storage Needs a lot of practice An average student became expert on
remembering digit sequences:● After 1 year of regular training could remember over
80 digits after hearing them once
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Ideas
● How does all this apply to your work?
?
Nov, 2006 24Lenko Grigorov, Queen's University
Design for experts, but beware of the learning curve!
Expertise
Time of experience
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Integration of memory stores?
● How do working memory and long-term memory work together?
● Learning (WMLTM) See that the “Turn off computer” option is in the
“Start” menu Always click on the “Start” menu to turn off your
computer● Retrieval (LTMWM)
Notice that the terminal window appears frozen no matter what you press on the keyboard
Remember to try “Ctrl-Q” before rebooting
Nov, 2006 26Lenko Grigorov, Queen's University
Emergence of cognition?
● How do perception and memories work together?
● Bottom-up processing Crossing the street, see a car coming, run!
● Top-down processing About to cross the street, watch for oncoming
cars!● ...These processes must be integrated
Nov, 2006 27Lenko Grigorov, Queen's University
Attention
● Theories: Attention is necessary to glue sensations into a
coherent perception There is a single memory store (aka long-term
memory) and working memory is the section of that store to which we pay attention
Attention is the arbitrator between competing responses
Human capacity for attention is limited● Attention is a cognitive bottle-neck
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Attention as selector (1)
● Say the colors in which these words are written, fast
GREENYELLOWBLUE
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Attention as selector (2)
● Say the colors in which these words are written, fast
GREENYELLOWBLUE
Nov, 2006 30Lenko Grigorov, Queen's University
Ideas
● How does all this apply to your work?
?
Nov, 2006 31Lenko Grigorov, Queen's University
Types of problems
● Insight problems How to operate a new coffee machine? How to solve a crossword puzzle?
● Problems with gradual advancement How to solve a quadratic equation? How to get from Napanee,ON to Honolulu,HI? …can be viewed as a succession of small
insights
Nov, 2006 33Lenko Grigorov, Queen's University
Gradual advancement?
● How many of the problems you solve daily are of the sort: y = x^2 + 3 x +15.6
● Do you know in advance what you want to get? Looking for a room to rent:
● Cheap● Clean● Close to campus
...ended up in an expensive room at a rundown shack, but with awesome housemates?
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Optimal solution?
● Einstellung: mechanization of thought
In order to call the elevator to go down from the 6th floor, you press the “down” button even though the elevator will go to the 7th floor first
If you press the “up” button, the elevator will stop on the 6th floor first and, once inside, you can tell it to go down
● Repeated use of a procedure leaves humans “blind” for better solutions
Nov, 2006 35Lenko Grigorov, Queen's University
Logic?
● Each card has a letter on one side and a number on the other.
● Which cards have to be flipped to verify the rule: If there is a vowel on one side, there is an
even number on the other.
● 79% “E” or “E,4”... 4% “E,7”
E K 74
Nov, 2006 36Lenko Grigorov, Queen's University
Do you agree?
● Wars are prosperous.● Prosperity is desirable.● Thus, wars are desirable.
● All procrastinators do their work slowly.● All graduate students do their work slowly.● Thus, all graduate students are
procrastinators.
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Ideas
● How does all this apply to your work?
?
Nov, 2006 40Lenko Grigorov, Queen's University
How do we solve problems?
● State space Each possible configuration of the variables in a
problem defines a state. The space of all states may be enormous (or even infinite)
● Operations A transformations of the variables leading from
one state to another Physical actions, induction steps, etc…
● Tree exploration Initial state and goal state(s) Find a sequence of operations which will
transform the initial state to one of the goals
Nov, 2006 41Lenko Grigorov, Queen's University
Tree exploration (tic-tac-toe)
......
...
Initial state
Goal state
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Heuristics
● Rules used to explore the tree. Brute-force Random
● Means-end analysis Must be able to evaluate the difference between
any state and the goal At each step, choose the operation that reduces
the difference most ...analogous to hill climbing, but back-tracking is
applied when stuck● If the person can recognize they are stuck!
Nov, 2006 43Lenko Grigorov, Queen's University
Satisficing
● When does problem solving end? We find a solution. OR We can’t find a solution within the portion of the
state space we can explore.● However
Is the solution we find the real/most optimal solution? Are we able to recognize the solution?
● How do we cope with so much uncertainty? Use satisficing
● Proclaim a discovered solution is “good enough” That’s what we do every day with (almost) all
problems
Nov, 2006 44Lenko Grigorov, Queen's University
Does it matter what representation we use?
● Representation = Data + Operations
● Verbal = 1D access, Image = 2D access
● There is no “good” and “bad” representation There is “suitable” and “unsuitable”
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Verification Bias
● How do we check for the validity of a solution?
● Given a hypothesis A B and having A Humans tend to generate examples of B and
check if they are valid Little effort is put into generating examples of B
and checking if they are valid● Debugging GUIs:
Click on all menus as intended, no crash, ! What about clicking on the menus in the wrong
order?
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Ideas
● How does all this apply to your work?
?
Nov, 2006 47Lenko Grigorov, Queen's University
What about insight problems?
● Theories for why incubation helps Johnson-Laird: selecting which constraints on
the solution to remove Simon: looking for the correct problem
representation Others:
● Alleviation of Einstellung● Recovering from fatigue● Gaining new experiences● Unconscious work on the problem
Nov, 2006 48Lenko Grigorov, Queen's University
Conclusions
● Remember: The designer knows their product The user has no experience
● Human users: Have a limited capacity for attention Take shortcuts whenever possible Make errors
● If an error is possible, someone will make it for sure!
● Most importantly: Validate your design decisions by testing with real users!