Human Factors & Problem Solving Cognitive Psychology 4 Computer Scientists interactive seminar Lenko Grigorov School of Computing, Queen's University

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


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)


Shortest path?


Shortest path.

Algorithmic solution: 14! = 87 178 291 200 optionsHuman solution: 2 sec.


Human Cognitive Machine

PerceptionAttention


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


Physical acuity

● One cannot expect acute perception of everything on the screen

● However, good sensitivity to change in the peripheral vision Attention is attracted


Perceptual assembly

● What & where pathways● Feature extraction and integration (Treisman)

shape

color

locationat

tent

ion

school bus


Pop-out

● Immediate perception of irregularities

● Doesn't work when irregularities involve more than one feature!


Gestalt dog

● The whole is more than the sum of its parts.


Gestalt principles

Proximity

Similarity

Continuity


Ideas

● How does all this apply to your work?

?


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


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


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


Ideas


?


Design for experts, but beware of the learning curve!

Expertise

Time of experience


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


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


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


Attention as selector (1)

● Say the colors in which these words are written, fast

GREENYELLOWBLUE


Attention as selector (2)

● Say the colors in which these words are written, fast

GREENYELLOWBLUE


Ideas


?


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


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?


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


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


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.


Ideas


?


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


Tree exploration (tic-tac-toe)

......

...

Initial state

Goal state


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!


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


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”


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?


Ideas


?


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


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!

Documents

Human Factors & Problem Solving Cognitive Psychology 4 Computer Scientists interactive seminar Lenko Grigorov School of Computing, Queen's University