Post on 16-Jan-2016
description
Anna Kolesnichenko
Songmei Han
The Growth of Cognitive The Growth of Cognitive Modeling in HCI Since GOMSModeling in HCI Since GOMS
OverviewOverview
GOMS as cognitive modelingAdvances in modeling specific serial
componentsExtensions of the basic frameworkWhat Cognitive Modeling in HCI can
and cannot do
Cognitive modelingCognitive modelingthe progress in modeling the kind of
cognition involved in HCI– basic and advanced sets of parameters
account for the time of given activities
– formal modeling in grammars and production systems
Error production Time to learn Savings from previous learning
– critical path analysis Specification of interacting processes and their
durations
Cognitive ModelsCognitive ModelsPredict how users will interact with
proposed designsConstrain the design spaceAnswer specific design decisionsEstimate total time for task performanceProvide base for calculating training time
and designing training documentationDetermine stages of activity that take the
longest time or produce the most errors
Cognitive modeling (cont.)Cognitive modeling (cont.)Method used for design, evaluation and
trainingGaps in understanding the process of
interacting with computers– Human learning– Design of consistent user interfaces– Error production and management– Interpretation of visual displays for meaning– Concurrent vs. sequential processes
Gaps in cognitive theoryGaps in cognitive theory
Fails to capture– User’s fatigue– Individual differences– Mental workload– Change expected in work life– User’s judgment of the acceptability of the
software
Analytic models of human Analytic models of human performance with computersperformance with computers
1980-1983 – Card, Moran and Newell - significant advance from modeling in cognitive psychology– modeled together many of the processes
contributing to the full cycle of perception to action
– described in enough detail the knowledge necessary to perform a task
– Enabled to generate predictions about human behavior in real, naturalistic tasks
FrameworkFramework
Two key components– Model Human Processor (MHP)
General characterization of the human information-processing system
– System architecture
– Quantitative parameters of component performance
– GOMS A way of describing what the user needs to know to
perform computer-based tasks
GOMSGOMS
A family of modelsDescribes
– The knowledge necessary– Four cognitive components of skilled
performance in tasks Goals Operators Methods Selection rules
Original GOMS FrameworkOriginal GOMS Framework
Focus: Selection of
methods from memory Time to specify
and execute an action
Assumptions Skilled user Serial sequence of independent cognitive operations and
motor activities
The method Predict a time it takes a user to execute a task A task is based on retrieving plans from long-term memory A method is chosen from available methods depending on
the features of the task Execute motor movements necessary
Time parameters for external actions were estimated from empirical data
The GOMS MethodThe GOMS Method
ExampleExample
Parameters: k – keystroke: 280 msec M - mental operator: 1.35 sec P – pointing: 1.1 sec H – moving hands: 400 msec
Example:
sum ( a , b )
Mkkk MkMkMkMkMk
Total = 6M’s + 8 k’s = 6(1.35) + 8(.280) = 10.34 sec
Limitations of GOMSLimitations of GOMS Limited range of domains Applied to skilled users only Accounts for performance but neither learning nor
recall Focused on errorless performance Gives little account of cognitive processes Focused of sequential tasks while many processes
occur in parallel Does not address mental workload Disregards fatigue that users experience Does not account of individual differences among
users
Advances in modeling specific Advances in modeling specific serial componentsserial components
1983 – further research based on GOMS methodology– Serial processing– Time parameters are constant across tasks
Incorporated relevant cognitive psychology factors
Empirical work based on studies of entering editor commands, formulas in spreadsheets, etc.
Classes of parametersClasses of parameters
motor movementperceptionmemorycognition
Motor MovementsMotor Movements
Keying
Moving a mouse
Hand movement
KeyingKeyingTime to enter a keystroke in a normal
typing taskValue depends on
– The skill level of the typist– Frequency with which a key is used– Predictability and continuity of the text
Example– Skilled typist – 80msec/keystroke– User unfamiliar with the keyboard – 1200 msec
/keystroke
Moving a MouseMoving a MousePointing with a mouse at objects at various
distances and of various target sizes.Derived from empirical experiments.Fitts’s law:
– T = 1.03+.096 log2(D/S+.5)
– applied to nested menus:
T = .81+.21 log2(D/S+.5)
Hand MovementsHand Movements
Time needed to move from the space bar of the keyboard until the pointing control begins to move the cursor.
Large-muscle movementCharacterized by Fitts’s lawEmpirically, T = 360 msec
PerceptionPerception
Recognition of features of the current task and assessment of some parameters necessary to do a task
Examples:– Time to respond to a brief light = 100 msec
(50-200 msec depending on intensity)
– Time to recognize a 6-letter word = 340 msec– Time for the eye to jump to next location
= 320 msec
Memory and Cognitive Memory and Cognitive ProcessesProcesses
Memory retrieval
Executing steps in a mental procedure
Choosing among methods
Memory RetrievalMemory Retrieval
Time to retrieve the next unit of information– well-known units– from long-term memory to working memory
A repeated act speeds up memory access
Memory Retrieval ExampleMemory Retrieval Example
Retrieve a command name or delimiter 1350msec
Retrieve a random command abbreviation
1200msec
Retrieve the next part of a formula 1100msec
Repeated retrieval of same command 660msec
Executing Steps in a TaskExecuting Steps in a Task
GOMS catalogues:the retrieval of goal and its subgoalsthe decision to select a methodthe retrieval of the motor movementsthe execution of each command
componentProduction system formalism - explicit
representation
Choosing Among MethodsChoosing Among Methods
The more choices – the longer the expected response time
Empirical estimations of time vary
(1.3 – 4.6 sec)
Composite PerformanceComposite Performance
A task:
enter a block of values(2 digits)Mouse method- enter each value, point to
the next cell with a mouseMenu method - <ret> key advances cursor
automatically to the next cell. Use mouse only to go to the next line
Empirical solutionEmpirical solution
Empirical results:Mouse method
4.19 sec per cellMenu method
2.46 sec per cell
2.81 sec to start each line
GOMS solutionGOMS solutionMouse method
moving the hand to the mouse 360 msec
clicking the mouse 230 msec
moving the hand to the keyboard 360 msec
retrieving digits 1200 msec
typing digits 460 msec
retrieving the end action 1200 msec
typing the <ret> key 230 msec
Total 4040 msec
3% error of 4.19 sec empirical result
Menu method – starting a new line:
moving hand to mouse 360 msec
pointing to a new line 1500 msec
clicking the mouse 230 msec
moving hand to keyboard 360 msec
Total 2450 msec
13% error of 2.81sec empirical result
GOMS solution (cont.)GOMS solution (cont.)
GOMS solution (cont.)GOMS solution (cont.)
Menu method – typing a number into a cell:
retrieving two digits 1200 msec
typing two digits 460 msec
retrieving the end action 1200 msec
typing the <ret> 230 msec
Total 3090 msec
26% error of 2.46 sec empirical result
Pros and cons of the methodPros and cons of the method
Challenged based on inclusion or exclusion or an operation (esp. mental)
Achievements– within an average of 14% error of the observed
values– accurate enough to be useful
SummarySummary
Problems with GOMS:– Serial process assumption– Independent task assumption
Served well in a variety of basic computer-based tasks
Extension of the Basic Extension of the Basic FrameworkFramework
Learning and Transfer– Time to learn– Transfer from one system to the other
Analysis of errors: Workload in Working Memory
Parallel ProcessesModeling parallel processes with critical
path analysis
Modeling in extended workModeling in extended work
Modeling of grammatical rules– What knowledge a user must have before
translating from goals to actions in a system?– Similar to goal decomposition and methods in
GOMS.– Provide a countable entity:
The number of rules
Task-Action Grammar (TAG)Task-Action Grammar (TAG)
Feature Possible values
Direction Forward, backward
Unit Character, word
Task[direction, unit] Symbol[Direction]+ Letter [Unit]
Symbol[forward] “cntl”
Symbol[backward] “meta”
Letter[word] “W”
Letter[character] “C”
Task-Action Grammar (TAG)Task-Action Grammar (TAG)
Goals Action
Move cursor one character forward
Cntl-C
Move cursor one character backward
Meta-C
Move cursor one word forward
Cntl-W
Move cursor one word backward
Meta-W
Production system Production system
Make underlying knowledge explicitOnce written, the accuracy and
completeness can be checked by running the program
Program can be used to predict both errors and learning time behavior
Rules for writing a SQL join queryRules for writing a SQL join query
Rule 1: StartUp. SeeIfJoinNeededIF
GOAL SeeIfJoinNeeded
Not (NOTE SeeingIfJoinNeeded TRUE
THEN
Add NOTE SeeingIfJoinNeeded TRUE
Add STEP CountTables
Rules for writing a SQL join queryRules for writing a SQL join query
Rule 2: CountTablesIF
GOAL SeeIfJoinNeeded
STEP CountTables
THENDo Task Count NumberOfTables * NumberOfTables
Add NOTE NumberOfTables * NumberOfTablesDelete STEP CountTablesAdd STEP AddJoinNote
Rules for writing a SQL join queryRules for writing a SQL join query
Rule 4: IfNumberOfTablesNot =2, ThenCleanUp
IF GOAL SeeIfJoinNeededSTEP AddJoinNoteNOTE NumberOfTables 1
THENDelete SETP AddJoinNoteDelete NOTE NumberOfTables ?NumberOfTablesAdd STEP Cleanup
Use of Production RulesUse of Production Rules
IF part:Check for a match between the rule’s condition and the current goal and the current notes in working memory (WM).
THEN part:If there is a match, execute THEN part action to add and delete NOTES and STEPS to or from WM.
Time to LearnTime to Learn
Kieras & Polson– Study learning under highly restrictive and
controlled condition– Determine the number of steps in a procedure – The time to learn each step is 30 second– The start-up time is 30 to 60 minutes.
Time to Learn (cont)Time to Learn (cont)
Results from from widely different situations and labs are at the same order of magnitude.
The number of rules is less critical than whether the features of those rules follow real-world features encoded in user’s memory.
Problem: how to quantify the learning time in more naturalistic situations.
Transfer of TrainingTransfer of Training
Production is the unit of learning. The number of productions shared by the two
systems can predict the amount of transfer. Time to master a new procedure is a function of
the number of new production to be learned. Specify the exact effects of consistent design
across system and assess the relative costs of different degrees of consistency among procedures.
Transfer Predicted by the number Transfer Predicted by the number of new rules to be learnedof new rules to be learned
Analysis of ErrorsAnalysis of Errors
Cause of errors:– Working Memory (WM) overload– Production systems are used to estimate the
contents of WM and the resident duration of each piece of information in WM.
– The more items in WM, the greater the likelihood of errors.
Systems with different WM Systems with different WM workloadworkload
Lotus 1-2-3– User has to find and remember the coordinates
of cells in the formula. (e.g. D23)
Interactive Financial Planning System (IFPS)– User can refer to a cells by name with adjective
(e.g. previous) to indicate relative location. No need to remember the coordinates.
WM Load for Different WM Load for Different SystemsSystems
Col Name
Row No.
Operator Var Name
Var Name
Var Name
Pointer Pointer Pointer Pointer Pointer Row No.
WM
Time
Position Naming (e.g. B22)Formula with cells in the same column
Operator Var Name
Var Name
Var Name
Pointer Pointer Pointer Pointer Pointer Row No.
WM
Time
Keyword Naming (e.g. Previous Sales)Formula with cells in the same column
WM Load and Error WM Load and Error ProbabilityProbability
The higher the WM load, the more errors– Lotus: 19 items in WM, 14% errors– IFPS: 14 items in WM, 6% errors.
When there are few than 8 items in WM, errors would be eliminated.– Magic number: 7
WM Load and Error WM Load and Error Probability (cont)Probability (cont)
SQL join query:
the more the intervening restriction statements, the higher the probability of forgetting the last crucial join statement.
No intervening restriction, 1.7% errors
2 intervening statements, 4.2% errors.
Problems with Error AnalysisProblems with Error Analysis
Do not distinguish between the peak load in WM and the duration of each item in WM.
People might use strategy to reduce WM load. (Notes, clues from the environment)
WM overload is not the only cause of errors.
Parallel Processes Parallel Processes
Reasons a serial model– Easy to quantify:
task time = sum of subcomponent time– Tradition in Cognitive modeling
Reasons for a parallel model– External signals appear in parallel. – Mental events can occur in parallel.– External actions can be done in parallel.
Examples of Parallel Examples of Parallel ProcessesProcesses
Rapid typing.Bank clerk enter the handwritten amount on
the check into the computer.Menu search in expert users.
The amount of parallel processes in a task depends on the skill level of the user.
Questions in Modeling Parallel Questions in Modeling Parallel ProcessesProcesses
What processes are occurring in parallel?Which processes depend on each other so
that they must occur in serial?The speed of which process is the limiting
factor for the task?
Critical Path AnalysisCritical Path Analysis
Analyze non-serial processes in timed cognitive tasks.
Model cascading mental and external process.
Analyze how three parallel processor resources (perceptual, cognitive, and motor) work with sequential dependencies.
Critical Path Analysis (cont)Critical Path Analysis (cont)
Parameters needed in critical path analysis – Component processes– Duration of each component process– Dependencies among the component processes
Total time taken by the task can be determined once the above parameters are all known.
Critical Path Analysis for 2 Critical Path Analysis for 2 TypistsTypists
Perceptual processor
Cognitive
Motor processor
Critical Path Analysis for Different UsersCritical Path Analysis for Different Users
What cognitive modeling in What cognitive modeling in HCI can and can not doHCI can and can not do
What cognitive model in HCI can do but more research is needed– Non skilled or casual users– Learning– Errors and mental workload– Cognitive processes– Parallel processes– Individual difference
What cognitive modeling in HCI What cognitive modeling in HCI can and can not do (cont)can and can not do (cont)
What cognitive modeling in HCI can not do– Estimate the impact of fatigue on performance– Assess people’s acceptance to the interface– Divide functionality between computer and
human: what human do best, what computer do best.
– How computer changes work and organizational life.
topic studied Extension possible
insufficient information
Different model
Non skilled user X
Learning X X
Errors X X
Cognitive Process X X X
Parallel Process X X X
Mental workload X
Functionality X
Fatigue X
Individual difference X
Acceptance X
Organizational life X