1. GOMS as a Simulation of Cognition
Frank Ritter, Olivier Georgeon
30 oct 2017

2. Cognitive architectures
"Brain emulator"
Simulates the computation we think the brain does (for doing a given task…).
Provides structures to store symbols
Provides instructions to manipulate symbols
Hypothesis: Goal-driven, Problem-solving, symbolic computation.
A way to combine what we know about users and apply.

3. GOMS Architecture
Explain each part. Note that there is some parallelism, but that much of most tasks are simply serial.
You can also point out that the previous chapters provide details on most of these boxes.

4. Example: Check email Procedure check_emails Goal Login Goal read_email
Goal memorize_sender's_name
Goal read_ _body
If Needed(), Goal replay_
Goal reply_ (x)
Selection rule Select_appropriate_formulation(x)
Goal reply_ _friend
Operator Type (Hi <x>) …
Goal reply_ _familly
Operator Type (Dear <x>)
Loop to read_ / Repeat Goal read_
Goal: Logout
Note: Needed ()’s will be translated as a mental op, but is usually more complex
Refer them to Kieras’ manual, which is a good manual.

5. Mental operations and contents
Visual buffer
Long term memory
Perceived_item: John
(John, relation, friend)
(Jack, relation, family)
( , name, John)
Not a complete list, but a sample of what is used by a use.
Goals
Selection rule
Reply_ _friend
Reply_ _family
Memorize_sender's_name …
If Perceived_item = X
And (X, relation, friend)
Then Process goal reply_ _friend

6. How To Use GOMS Analyze hierarchical structure of a task
coarse analysis focuses more on the cognitive structure of a task
fine analysis focuses more on the structure imposed by the specific interface design
Analyze alternative methods of interaction
Assign operators to base level goals
Assign times to operators
Sum the operator times to get sum for task
Look for excessive time
Look for duplicated time
Look for wasted time
Look for non-parallel construction on parallel tasks
A-D go on a ways as the analysis have lots of ways to show how to improve
Ahh, look for where the system response time is killing you

7. GOMS Operator Times 280 ms 1,500 ms 300 ms 230 ms 1,200 ms 25,000 ms
Press key on keyboard
280 ms
Use mouse to point to object on screen
1,500 ms
Move hand to pointing device
300 ms
Move eyes to location on screen
230 ms
Retrieve item from memory
1,200 ms
Learn a single step in a procedure
25,000 ms
Select among methods
More available in FDUCS, GOMSL and CM&N

8. Summary of GOMS
A method to describe tasks and how a user performs those tasks with a specific design
bridges task analysis with a specific interface design
assumes error-free, goal-directed, and rational behavior
Views humans as information processors
small number of cognitive, perceptual, and motor operators characterize user behavior
To apply GOMS
analyze task to identify user goals (hierarchical)
identify operators to achieve goals
sum operator times to predict performance

9. KLM Times To do the KLM, keep track of 80-1200 ms 1,100 ms 400 ms
Press key on keyboard ms
Use mouse to point to object on screen
1,100 ms
Move hand to pointing device
400 ms
Mental OP:
Retrieve item from memory
1,350 ms
Select among methods
1,200 ms
Slightly different numbers, because slightly different theory

10. M Heuristics placement
Do all physical ops
0. Insert Mop before all K’s not part of strings (e.g., shift to new field) and P’s that select a command (not argument)
Remove all Mops fully anticipated as part of commands (PMK-> PK)
Remove all after first letter of a command (CR M K M K M K M-> CR M K K K K)
Remove redundant command terminators (CR M command M CR -> CR M command CR)
Don’t remove variable terminators (no change)

11. Conclusion: KLM and GOMS, an inexpensive way to improve about interfaces
Cheap way to evaluate expert, error-free performance (GOMS) in interfaces
Cheaper way to evaluate interfaces (KLM)
If done fairly, typically tells you the best interface
Typically tells where improvements are possible
Less movements, less keys, less Mop
Keep parallel and consistent
Shift from mouse to keyboard for experts
Apply Fitts law where appropriate to improve targets
Change users (faster Ks) or hardware (better mouse or autokeypress, etc.)