GOMS - Zentrum Mensch-Maschine-Systeme - TU Berlin

Modellbildung und 

Simulation in MMS 2 

GOMS 

KLM-GOMS 

NGOMSL 

Tutorial ACT-R 

11. Mai 2004 

Leon Urbas & Sandro Leuchter 

1

Thema 

1 

Selection of ... 

Cognitive Analysis of Dynamic Performance: 

Cognitive process analysis and modeling 

Workshop Presented at the HFES/IEA-2000 

Conference in San Diego, CA 

Wayne D. Gray, Ph.D. 

Deborah A. Boehm-Davis, Ph.D. 

Modellbildung und Simulation in 

George Mason University 

Mensch-Maschine-Systemen 2 

Human 

sandro@zmms.tu-berlin.de 

Factors & Applied Cognitive Program 

2


Definition of GOMS 

Characterization of a task in terms of 

The user's Goals 

The Operators available to accomplish those goals 

Methods (frequently used sequences of operators and 

sub-goals) to accomplish those goals, and 

If there is more than one method to accomplish a goal, 

the Selection rules used to choose between methods. 


Mensch-Maschine-Systemen 2 sandro@zmms.tu-berlin.de 3


What GOMS Is 

GOMS is a task analysis technique 

Very similar to Hierarchical Task Analysis 

(Indeed, GOMS is a hierarchical task analysis 

technique) 

Hard part of task analysis is goal-subgoal 

decomposition 

• Hard part of GOMS is goal-subgoal decomposition 

Different members of the GOMS family 

provide you with different sets of operators 

• With established parameters 

• But set is not complete (extensionable) 




Level 1: Task Analysis: Task Subtasks Subtasks 

TASK 

SUBTASKs 

SUBTASKs 

SUBTASKs 

Complete 

Session #1 

Scenario 

#1 

Hook 

Target 

ID#1 

Hook 

Target 

ID#2 

Complete 

Argus Prime 

Experiment 

Scenario 

#2 

Complete 

Session #2 

Hook 

Target 

ID#3 

Scenario 

#3 

• • • • 

Complete 

Session #3 

• • • • 

Hook 

Target 

ID#n 

Scenario 

#n 

Duration 


Mensch-Maschine-Systemen 2 sandro@zmms.tu-berlin.de 5 

5 hr 

1-2 hrs 

12-30 min 

30 sec to 3 min


Level 2: Subtask Unit Tasks 

yes 

Target 

acquisition 

Classified? 

no 

Target 

classification 

Feedbk 

check? 

yes 

Feedback check 



no


Level 3: Cognitive Task Analysis: Unit Tasks Activities 

yes 

Target 

acquisition 

Classified? 

no 

Target 

classification 

Feedbk 

check? 

yes 

Feedback check 

no 

Classified? 

Method for goal: Determine if target is classifed 

Step 1 Select target by mouse click 

Step 2 Note target ID# 

Determine if radio button in info 

Step 3 window is black 

Verify that info window id# is same 

Step 4 as target id# 




Level 4: Embodied Cognition: Activity Microstrategy 

Method for goal: Determine if target is classifed 

Step 1 Select target by mouse click 

Step 2 Note target ID# 

Step 3 

Step 4 

Determine 50 50 if radio button in info 

50 50 

window verify is black initiate attend retrieve 

Verify crsr @ that info mouse window trgt id# is trgt same ID# 

target down ID# 

as target id# 

100 

mouseDn on 

target 

http://hfac.gmu.edu/~mm 

0 

50 

Information Window is 

updated 

attend 

visual 

initiate 

eye 

mvmt 



50 

100 

30 

perceive black 

radio button 

eye mvmt 

50 

verify 

trgt 

50 

retrieve 

trgt ID# 

50 

verify 

trgt 

ID#


Level 5: Microstrategies Elements 

Production Rules 

Declarative memory elements 

Internal (created on RHS of production rules) 

External (created by shifts of attention in the 

external environment) 

Nicht im Bereich von GOMS! 




Level 6: Elements Parameters 

w -- amount of attentional capacity 

d -- decay rate 

s -- fluctuations in the strength of 

declarative memory elements 

rt -- retrieval threshold 

Nicht im Bereich von GOMS! 




Definition of GOMS 

Characterization of a task in terms of 

The user's Goals 

The Operators available to accomplish those goals 

Methods (frequently used sequences of operators and 

sub-goals) to accomplish those goals, and 

If there is more than one method to accomplish a goal, 

the Selection rules used to choose between methods. 




Definition Example of of G-O-M-S GOMS 

To carry out a GOMS analysis of the 

following task involving a digital clock: 

• Set the clock 

Top level goal: SET CLOCK 




Example of G-O-M-S: Goals 

Goals and subgoals 

Set Clock 

Set Hour Set Min 




Example of G-O-M-S: Operators 

Operators are the most elementary steps in 

which you choose to analyze the task. 

Reach button 

Hold button 

Release button 

ClickOn button 

Decide: if then 

Verify 




Example of G-O-M-S: Methods 

Top-level user goals 

SET-CLOCK 

Method for goal: SET-CLOCK 

Step 1. Hold TIME button 

Step 2. Accomplish goal: SET-HOUR 

Step 3. Accomplish goal: SET-MIN 

Step 4. Release TIME button 

Step 5. Return with goal accomplished 

Method for goal: SET- 

Step 1. ClickOn button 

Step 2. Decide: If target = current , then return with 

goal accomplished 

Step 3. Goto 1 




Example of G-O-M-S: Selection 

No selection rules in this example as this clock has only 

ONE method for accomplishing each goal, but . . . 

Selection rule for goal: SET-HOUR 

If target HOUR ≤ 4 hours from current HOUR, 

then Accomplish Goal: ClickOn HOUR 

If target HOUR > 4 hours from current HOUR, 

then Accomplish Goal : Click&Hold HOUR 




Applications of GOMS 

Case 1. Design of mouse-driven text editor 

Case 2. Directory assistance workstation 

Case 3. Space operations database system (for orbital objects) 

Case 4. Bank deposit reconciliation system. 

Case 5. CAD system for mechanical design. 

Case 6. Television control system. 

Case 7. Nuclear power plant operator's associate. 

Case 8. Intelligent tutoring system. 

Case 9. Industrial scheduling system. 

Case 10. CAD system for ergonomic design. 

Case 11. Telephone operator workstation. 

List compiled by John & Kieras (1997a). 




Applications GOMS as Analytic of GOMS Modeling 

GOMS analysis produces a model of behavior 

Given a task, the model predicts the methods, 

or sequences of operators, that a person will 

perform to accomplish that task 

Can look at the GOMS model in different ways 

to qualitatively and quantitatively assess 

different types of performance 




GOMS Scope as of GOMS: Analytic What Modeling it can do 

Predict the sequence of operators an expert 

will perform 

Predict performance time of expert users - 

even in real-world situations 

Predict learning time in relatively simple 

domains 

Predict savings due to previous learning 

Help design on-line help and manuals 




Scope of GOMS: What it can can do 

GOMS has been applied to both: 

User-driven interaction 

“Situated” or event-driven interaction 




Scope of GOMS: What it might do 

Research has made progress on 

Predicting the number of some types of errors 

• see discussion in: Gray, W. D. (2000). The nature 

and processing of errors in interactive behavior. 

Cognitive Science, 24(2), 205-248. 

Predicting the effects of display layout on 

performance time 




Scope of GOMS: What it can can’t do do 

Predict problem-solving behavior 

Predict how GOMS structure grows from 

user experience 

Predict behavior of casual users, 

individual differences... 

Predict the effects of fatigue, user 

preference, organizational impact... 




General Factors to consider 

When deciding what type of GOMS model 

you need, you must consider... 

what control structure 

what level of analysis 

whether to approximate behavior with serial 

or parallel processes 

...different uses of GOMS models lead to 

different values of these factors 

These factors will be a recurring theme 




GOMS Family of Analysis Methods 

Keystroke-Level Model 

CMN-GOMS 


CMN-GOMS for Highly Interactive 

Tasks 

CPM-GOMS 









Tasks 










Tasks 





Intro 

The simplest of all GOMS models: OM only!!! 

No explicit goals or selection rules 

Operators and Methods (in a limited sense) only 

“Useful where it is possible to specify the user’s 

interaction sequence in detail” (CMN83, p. 259). 

Control structure: Flat 

Serial or Parallel: Serial 

Level of Analysis: Keystroke-level operators 




Overview 

Step 1: Lay out assumptions 

Step 2: Write out the basic action sequence (list the 

keystroke-level physical operators involved in doing the 

task) 

Step 3: Select the operators and durations that will be 

used 

Step 4: List the times next to the physical operators for the 

task 

Step 4a: If necessary, include system response time 

operators for when the user must wait for the system to 

respond 

Step 5: Next add the mental operators and their times 

Step 6: Sum the times of the operators 




Operators 

K: Keystroke 

T(n): Type a sequence of n characters on a 

keyboard 

P: Point with mouse to a target on a display 

B: Press or release mouse button 

BB: Click mouse button 

H: Home hands to keyboard or mouse 

M: Mental act of routine thinking 

W(t): Waiting time for system to respond 




Mentals 

“M operations represent acts of mental 

preparation for applying physical operations. 

Their occurrence does not follow directly from 

the physical encoding, but from the specific 

knowledge and skill of the user” p. 267 

“The rules for placing M’s embody psychological 

assumptions about the user and are necessarily 

heuristic, especially given the simplicity of the 

model” p. 267. 




Heuristics for Mentals 

Basic psychological principle: physical operations in 

methods are chunked into submethods. 

RULE 0: Insert M’s in front of all K’s or B’s that are not part of 

argument strings proper (e.g., text or numbers). Place M’s in front 

of all P’s that select commands (not arguments) or that begin a 

sequence of direct-manipulation operations belonging to a 

cognitive unit. 

• Pointing to a cell on a spreadsheet is pointing to an argument -- no M 

• Pointing to a word in a manuscript is pointing to an argument -- no M 

• Pointing to a icon on a toolbar is pointing to a command -- M 

• Pointing to the label of a drop-down menu is pointing to a command -- M 




Heuristics for inserting mental operators 

Rules 1-4 are heuristics (rules of thumb) 

for deleting mentals 

“A single psychological principle lies behind 

all the deletion heuristics . . . physical 

operations in methods are chunked into 

submethods” p. 268 





Basic psychological principle: physical operations 

in methods are chunked into submethods. 

RULE 0: Insert M’s in front of all K’s or B’s that are not part of 

argument strings proper (e.g., text or numbers). Place M’s in 

front of all P’s that select commands (not arguments) or that 

begin a sequence of direct-manipulation operations belonging to 

a cognitive unit. 

RULE 1: If an operator following an M is fully anticipated 1 in an 

operator just previous to M, then delete the M (e.g., PMK --> PK or 

PMBB --> PBB). 

• That is, the “M” drops out because the “P” and “BB” belong 

together in a chunk -- mental unit. 

• The button press “BB” is fully anticipated as the cursor is 

being moved to the target. 







RULE 0: Insert M’s in front of all K’s or B’s that are not part of argument strings 

proper (e.g., text or numbers). Place M’s in front of all P’s that select commands 

(not arguments) or that begin a sequence of direct-manipulation operations 

belonging to a cognitive unit. 

RULE 1: If an operator following an M is fully anticipated 1 in an operator just previous 

to M, then delete the M (e.g., PMK --> PK or PMBB --> PBB). 

RULE 2: If a string of MK’s or MB’s belongs to a cognitive unit (e.g., the 

name of a command), then delete all M’s but the first. 

• Works with command names -- but what is a command name in a GUI 

interface? 

• Physical actions: P(File)+ B + P(Save) + B 

• RULE 0: MP + MB + MP + MB 

• RULE 1: MPB + MPB 

• Does rule 2 apply to eliminate the middle mental? MPBPB ? 













RULE 2: If a string of MK’s or MB’s belongs to a cognitive unit (e.g., the name of a 

command), then delete all M’s but the first 

RULE 3: If a K is a redundant terminator (e.g., the terminator of a command 

immediately following the terminator of its argument), then delete the M in 

front of it. 

• Applies to clicking OKAY in dialog buttons after you select a 

command; e.g., in Powerpoint, you have selected text, gone to the 

FORMAT:FONT palette, clicked on bold, and now point and click on 

OKAY -- pointing to and clicking on OKAY is PBB, not MPBB 













RULE 2: If a string of MK’s or MB’s belongs to a cognitive unit (e.g., the name of a 

command), then delete all M’s but the first 


immediately following the terminator of its argument), then delete the M in front of it. 

RULE 4: If a K terminates a constant string (e.g., a command name), then 

delete the M in front of it; but if the K terminates a variable string (e.g., an 

argument string), then keep the M in front of it. 





The four heuristics do NOT capture the 

notion of method chunks precisely -these 

are only approximations 

Ambiguities: Is something “fully 

anticipated” or is something else a 

“cognitive unit”? 

Much of this ambiguity stems from 

variations in expertise of the users we are 

modeling 





Basic psychological principle: physical operations 

in methods are chunked into submethods. 

RULE 0: Insert M’s in front of all K’s or B’s that are not part of argument 

strings proper (e.g., text or numbers). Place M’s in front of all P’s that 

select commands (not arguments) or that begin a sequence of directmanipulation 

operations belonging to a cognitive unit. 

RULE 1: If an operator following an M is fully anticipated 1 in an operator 

just previous to M, then delete the M (e.g., PMK --> PK or PMBB --> PBB). 

RULE 2: If a string of MK’s or MB’s belongs to a cognitive unit (e.g., the 

name of a command), then delete all M’s but the first 


immediately following the terminator of its argument), then delete the M in 

front of it. 

RULE 4: If a K terminates a constant string (e.g., a command name), then 

delete the M in front of it; but if the K terminates a variable string (e.g., an 

argument string), then keep the M in front of it. 




KLM--mentals: example 1. 

Example: SET COLUMN WIDTH 5 

List the keystroke level physical operators involved in doing the task 

KKKKKKKKKKKKKKKKKKK (19 K’s) 

RULE 0 

M+KKKK+M+KKKKKKK+M+KKKKKK+K+M+K or 

M+4K(set_)+M+7K(column_)+M+6K(width_)+1K(5)+M+1K() 

RULE 1 

no change in this example 

RULE 2 

M+17K(set_column_width_)+1K(5)+M+1K() 

RULE 3 

No change in this example 

Rule 4 

No change in this example 




KLM--mentals: example 2 

Example: spellcheck “catelog” 

List the keystroke level physical operators involved in 

doing the task 

P+BBBB+P+BB (where BB is a mousedown + mouseup, 

and BBBB is a doubleclick) 

RULE 0 

P+M+BBBB+M+P+BB 

RULE 1 

n/a 

RULE 2 

n/a (“catelog” + spellcheck do not form a cognitive unit) 

RULE 3 

n/a 

RULE 4 

n/a 




KLM--mentals: example 3 

Example: save a file on a Mac using menus 

List the keystroke level physical operators 

involved in doing the task 

P+B+P+B 

RULE 0 

M+P+M+B+M+P+M+B 

RULE 1 

M+P+B+M+P+B 

RULE 2 

n/a or M+P+B+P+B ??? 

Issue: Is this FILE-->SAVE menu selection a 

single cognitive unit or two? 




Operators 

operator abbrev duration 

mental M 1200msec 

keystroke- K 280msec 

mouseDown or Up B 100msec 

click (mouseD & Up) BB 200msec 

homing H 400mec 

pointing w/mouse P 1100msec 

doubleClick BBBB 400msec 

Kieras, D. (1993). Using the keystroke-level model to 

estimate execution times. University of Michigan. 









Tasks 





Characterization 

Natural Language GOMS 

based on structured natural language 

notation and a procedure for constructing 

them 

models are in program form 

Control Structure: Hierarchical goal stack 

Serial or parallel: Serial 

Level of Analysis: As necessary for your 

design question 




NGOMSL - why? 

More powerful than KLM. Much more 

useful for analyzing large systems 

More built-in cognitive theory 

Provides predictions of operator 

sequence, execution time, and time to 

learn the methods 




NGOMSL - Overall Approach (1) 

Step 1: Perform goal/subgoal decomposition 

Step 2: Develop a method to accomplish each 

goal 

List the actions/steps the user has to do goal (at as 

general and high-level as possible for the current 

level of analysis) 

Identify similar methods/collapse where appropriate 

Step 3: Add flow of control (decides) 

Step 4: Add verifies 




NGOMSL - Overall Approach (2) 

Step 5: Add perceptuals, etc. 

Step 6: Add mentals for retrieves, 

forgets, recalls 

Step 7: Add times for each step 

Step 8: Calculate total time 




NGOMSL - Example 

Car clock 

Presetting radio stations 

simple 

perverse 




Car Radio example (1) 

Provides predictions of methods and operators used to complete a task. If 

you provide estimates of operator-duration, you can get predictions of 

error-free expert performance time. 

SEEK 

– TUNE + 

ON OFF 

PUSH CLOCK 

AM 

FM 

2:41 

1 2 3 

4 5 6 



EJ 

BASS 

– + 

TREBLE 

– + 

BALANCE 

L R 

FADE 

L R



Goal/subgoal hierarchy 

set 

mode 

turn knob depress knob 

(and keep it 

depressed) 

set clock 

set hour 

press tune 

“-” button 

set 

minute 

press tune “+” 

button 

release knob 





Assumptions 

User's hands are NOT on the buttons at the beginning. 

Time to move hand & arm to time change level is 

estimated by 2ft "reach" from Barnes (1963): 410 msec. 

D = device time, time for clock to move forward one 

number, = 500 msec (we estimate this on the next 

slide) 

I am assuming a 12-hr clock. Seems good assumption 

for a car clock. 

Radio is off at beginning and end. 

Begin knowing the time you want to set the clock to. 





D = device time, time for clock to move 

forward one number, = 500 msec 

Visual Perception 

Cognitive Operators 

Right Hand 

290 

perceive 

info (X) 

50 

verify 

info (X) 

Minimum time required to perceive 

clockTime=targetTime and to release the toggle lever 

50 

initiate release 

(X) 

release 

(X) 



100



stmt op tot 

time oper time time assumptions 

Method for goal: SET-CLOCK 

Accomplish goal: set Mode to 

0.1 0.10 

Step 1 set Clock 

Decide: If curHr°targetHr Then: 

Accomplish goal: Change Hour 

0.1 0.10 

Step 2 display 

Decide: If curMin°targetMin 

Then: Accomplish goal: Change 

0.1 0.10 

Step 3 Minute display 0.1 0.10 

Step 4 Release "vol/on/off" knob 0.1 B 0.10 0.20 

Step 5 Return with goal accomplished 0.1 0.10 





stmt op tot 


Method for goal: set Mode to set Clock 0.1 0.10 

Recall "vol/on/off" is 

retrieval from LTM or 

equivalent (location and 

perception of labels?) needed 

Step 1 modeSwitch 0.1 M 0.50 0.60 and takes - 500 msec 

For this example we assume 

that location is NOT known. If 

Decide: If location of 

known then tot. time for this 

modeSwitch is not known then 

step would be the stmt time, 

Step 2 Locate modeSwitch 0.1 M 1.20 1.30 0.10 sec 

Reach & Grasp "volume/on/off" 

source: Barnes, 1963, reach = 

Step 3 knob 0.1 R 0.48 0.58 410 msec, grasp = 070 msec 

Step 4 Turn knob 

Home thumb to "volume/on/off" 

0.1 T 0.34 0.44 source: Barnes, 1963 

Step 5 knob 0.1 H 0.40 0.50 

Step 6 Press and hold knob 0.1 B 0.10 0.20 






stmt 

op tot 


Method for goal: Change display 

Decide: If location of setTime 

switch is not known then Locate 

0.1 0.10 

Step 1 setTime switch 

Decide: If finger is NOT on 

setTime switch then: Reach to 

0.1 M 1.20 1.30 assume that loc is not known 

Step 2 setTime switch 0.1 R 0.41 0.51 

Step 3 

Retrieve-from-LTM that 

= "+ or -" 0.1 M 0.50 0.60 

retrieval from LTM or equivalent 

(location and perception of labels?) 

needed and takes - 500 msec 

Step 4 Determine current setting 0.1 P 0.32 0.42 

based upon cpm-goms analysis it should 

take 420 msec for eye to move to clock 

and for user to perceive the hour. 

Press and hold setTime switch 

cpm-goms calc. is -250 msec, go with 

Step 5 to 0.1 B 0.10 0.20 KLM 

System response time is 500 

msec/digit, this is enough time for Ss 

Hold until = 

to perceive and initiate keyUp 

Step 6 , (500 x #digits) W 

response. 

Step 7 Verify display 0.1 M 1.20 1.30 






time for SetClock goal 0.70 

time for setMode goal 3.82 

time for setHour from 1 to 10 9.03 

time to setMin from 56 to 50 31.53 

total 45.08 




PreSetting a station (1) 

Set Mode to 

Radio 

etc 

Select 

AM/FM 

General goal hierarchy for presetting a station 

Initiate 

seek 

PreSET Network 

Show 

Locate 

Station 

Identify 

Station Terminate 

seek 

Enter PreSet 

MODE 

Set PreSET 

Enter PreSet 

Button 

Exit PreSet 

MODE 





Set Mode to 

Radio 

etc 

Select 

AM/FM 

Goal hierarchy for optimal design 

Locate 

Station 

seek & 

identify 

PreSET Network 

Show 

Set PreSET 

press & hold 

preset button until 

sound returns 

Note differences between this and previous slide. 





MODEL 1: SETTING A PRESET TO A NETWORK SHOW - 

OPTIMAL DESIGN 

Method for goal: preset network show 

Step1: Decide: IF radio is not playing, THEN Accomplish goal: 

set-mode-to-radio 

Step2: Decide: IF show N.E. intended show, THEN Accomplish 

goal: locate-station 

Step3: Accomplish goal: set-preset 

Step4: Return with goal accomplished 

Method for goal: locate-station 

Step1: Decide: IF band N.E. desired band, THEN Accomplish 

goal: select AM/FM 

Step2: Accomplish goal: seek&identify 


Method for goal: select AM/FM 

Step1: Reach to button for desired band 

Step2: Press button for desired band 

Step3: Verify band correct 






Method for goal: seek&identify 

Step1: Reach to right side of "Seek" button 

Step2: Press "Seek" button 

Step3: Decide: IF show N.E. intended show, THEN Goto 2 

Step4: Verify show correct 


Method for goal: set-preset 

Step1: Reach to desired "Preset" button 

Step2: Press and hold "Preset" button 

Step3: Wait until sound returns 

Step4: Remove finger from "Preset" button 





PreSetting perverse (1) 

Set Mode to 

Radio 

etc 

Select 

AM/FM 

Enter 

seek 

mode 

Initiate 

seek 

seek & 

identify 

Goal hierarchy for perverse design 

Exit 

seek 

MODE 

PreSET 

Network Show 

Locate 

Station 

Enter 

delete 

MODE 

Delete old 

PreSET 

Enter PreSet 

Button 

Set PreSET 

Exit 

delete 

MODE 

Assign new 

PreSET 

Enter 

PreSet 

MODE 

Enter PreSet 

Button 

Exit 

PreSet 

MODE 





SEEK MODE 

SEEK 

– TUNE + 

ON OFF 

PUSH CLOCK 

Radio for Perverse Preset Design 

AM 

FM 

2:41 

1 2 3 

4 5 6 



EJ 

BASS 

– + 

ERASE PRESET 

MEMORIZE PRESET 

TREBLE 

– + 

BALANCE 

L R 

FADE 

L R



MODEL 2: SETTING A PRESET TO A NETWORK SHOW - 

PERVERSE DESIGN 

Method for goal: preset network show (s/a optimal) 

Step1: Decide: IF radio is not playing, THEN Accomplish goal: 

set-mode-to-radio 

Step2: Decide: IF show N.E. intended show, THEN Accomplish 

goal: locate station 

Step3: Accomplish goal: set-preset 


Method for goal: locate-station (s/a optimal) 

Step1: Decide: IF band N.E. desired band, THEN Accomplish 

goal: select AM/FM 

Step2: Accomplish goal: initiate-seek 


Method for goal: select AM/FM (s/a optimal) 

Step1: Put finger on button for desired band 

Step2: Press button for desired band 

Step3: Verify band correct 






Method for goal: initiate-seek 

Step1: Accomplish goal setMode-SEEK 

Step2: Accomplish goal: seek&identify 

Step3: Accomplish goal: exit seek mode 


Method for goal: setMode- 

Step1: Reach for button 

Step2: Press button 

Step3: Verify correct 


Method for goal: seek&identify (s/a optimal) 

Step1: Reach to right side of "Seek" button 

Step2: Press "Seek" button 

Step3: Decide: IF show N.E. intended show, THEN Goto 2 

Step4: Verify show correct 


Method for goal: set-preset 

Step1: Accomplish goal: delete-previous-preset 

Step2: Accomplish goal: assign-new-preset 






Method for goal: delete-previous-preset 

Step1: Accomplish goal: setMode-deletePreSet-on 

(setMode-) 

Step2: Accomplish goal: enter-preset-button 

Step3: Accomplish-goal: setMode-deletePreSet-off 

(setMode-) 


Method for goal: assign-new-preset 

Step1: Accomplish goal: setMode-preset-on (setMode- 

) 

Step2: Accomplish goal: enter-preset-button 

Step3: Accomplish-goal: setMode-preset-off (setMode- 

) 


Method for goal: enter-preset-button 

Step1: Reach to desired "Preset" button 

Step2: Press "Preset" button 





comparison of optimal and perverse 

Optimal Perverse 

number of different methods 6 11 

number of methods used 6 18 

number of different steps 21 38 

number of steps required 21 66

GOMS - Zentrum Mensch-Maschine-Systeme - TU Berlin

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