Cognitive Models

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Cognitive Models
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Agenda

• Questions
• Model Human Processor
• GOMS
• KLM-GOMS
• Project Group Time?

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Models of Human Cognition

• Human as information processing system
• Predict performance
• Dont describe actual cognition
• Formulated by Card, Moran and Newell in The
  Psychology of Human-Computer Interaction (1983)

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Other models

• Task analysis modeling human tasks
• Fitts Law modeling physical capabilities
  (movement time)
• Distributed cognition
• Situated action
• Activity theory

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Model Human Processor

• 3 systems perceptual, cognitive and motor
  systems
• Each system has processor and memory
• Principles of operation

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The MHP model
Perceptual System
Cognitive System
Motor System
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The MHP model

• What does MHP sound like?
• Not meant to explain how the human brain works
• Intended to help understand, predict and
  calculate human performance in human-computer
  interaction

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Perceptual System

• Create internal representations of physical
  sensations
• Stores temporary information in buffers
• Auditory Image Store, Visual Image Store
• Transfers info in buffers to WM

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Perceptual Processor

• Cycle time time between when stimulus is
  presented and when it is available in buffers
• Multiple similar stimuli can combine during one
  cycle
• Principle Cycle time varies inversely with
  stimulus intensity

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Cognitive System

• Connects inputs from Perceptual System to outputs
  of Motor System
• Handles learning, remembering, and problem
  solving
• Includes WM and LTM

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Cognitive Processor

• Recognize-act cycle contents of WM trigger
  actions in LTM which modify WM
• Principle CP cycle time is shorter when greater
  effort is induced by task or information. Cycle
  time diminishes with practice.

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Motor System

• Thought is translated into physical (muscular)
  actions
• Motor system corrections require cycles of
  perceptual and cognitive systems

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GOMS

• G
• O
• M
• S

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GOMS analysis

• Start by building goal decomposition
• Times can be assigned to individual operators to
  predict execution times
• Path lengths can be compared
• Performance can be verified against real use

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The GOMS family

• KLM GOMS
• CMN-GOMS
• Cognitive Complexity Theory
• Natural GOMS Language
• Cognitive Perceptual Motor-GOMS

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Cognitive Complexity Theory

• A flavor of GOMS that measures interface
  complexity
• Production rules
• Executable
• Performance
• measures of memory requirements

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Keystroke-Level Model (KLM)

• KLM - developed by Card, Moran Newell, see
  their book
• Skilled users performing routine tasks
• Assigns times to basic human operations -
  experimentally verified
• Based on MHP - Model Human Processor

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KLM Accounts for

• Keystroking TK
• Mouse button press TB
• Pointing (typically with mouse) TP
• Hand movement betweenkeyboard and mouse TH
• Drawing straight line segments TD
• Mental preparation TM
• System Response time TR

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Using KLM - Step One

• Decompose task into sequence of operations - K,
  B, P, H, D (no M operators yet R can be used
  always or not at all)

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Step One MS Word Find Command

• Use Find Command to locate a six character word
• H (Home on mouse)
• P (Edit)
• B (click on mouse button - press/release)
• P (Find)
• B (click on mouse button)
• H (Home on keyboard)
• 6K (Type six characters into Find dialogue box)
• K (Return key on dialogue box starts the find)

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Using KLM - Step Two

• Place M operators
• Rule 0a. In front of all Ks that are NOT part of
  argument strings (ie, not part of text or
  numbers)
• Rule 0b. In front of all Ps that select commands
  (not arguments)

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Step Two MS Word Find Command

• H (Home on mouse)
• MP (Edit)
• B (click on mouse button)
• MP (Find)
• B (click on mouse button)
• H (Home on keyboard)
• 6K (Type six characters)
• MK (Return key on dialogue box starts the find)

Rule 0b Pselects command
Rule 0b Pselects command
Rule 0a Kis argument
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Using KLM - Step 3

• Remove Ms according to heuristic rules
• (Rules relate to chunking of
  actions)
• Rule 1. Anticipated by prior operation
• PMK -gtPK (point and then click is a chunk)
• Rule 2. If string of MKs is a single cognitive
  unit (such as a command name), delete all but
  first
• MKMKMK -gt MKKK (same as M3K) (type run rtn is a
  chunk)
• Rule 3. Redundant terminator, such as )) or rtn
  rtn
• Rule 4. If K terminates a constant string, such
  as command-rtn, then delete M
• M2K(ls)MK(rtn) -gt M2K(ls)K(rtn) (typing ls
  command in Unix followed by rtn is a chunk)

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Step 3 MS Word Find Command
H (Home on mouse) MP (Edit) B (click on mouse
button) MP (Find) B (click on mouse button) H
(Home on keyboard) 6K (Type six characters) MK
(Return key on dialogue box starts the find)
Rule 1 delete M H anticipates P
Rule 1 delete M H anticipates P
Rule 4 Keep M
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Using KLM - Step 4

• Plug in real numbers from experiments
• K .08 sec for best typists, .28 average, 1.2 if
  unfamiliar with keyboard
• B down or up - 0.1 secs click - 0.2 secs
• P 1.1 secs
• H 0.4 secs
• M 1.35 secs
• R depends on system often less than .05 secs

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Step 4 MS Word Find Command

• H (Home on mouse)
• P (Edit)
• B (click on mouse button - press/release)
• P (Find)
• B (click on mouse button)
• H (Home on keyboard)
• 6K (Type six characters into Find dialogue box)
• MK (Return key on dialogue box starts the find)
• Timings
• H 0.40, P 1.10, B 0.20, M 1.35, K 0.28
• 2H, 2P, 2B, 1M, 6K
• Predicted time 6.43 secs

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Example MS Windows Menu Selection

• Get hands on mouse
• Select from menu bar with click of mouse button
• The pull down menu appears
• Select desired item from the pull down menu

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Step 1 MS Windows Menu

• H (Home on mouse)
• P (point to menu bar item)
• B (left-click with mouse button)
• P (point to menu item)
• B (left-click with mouse button)

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Step 2 MS Windows Menu - Add Ms

• H (get hand on mouse)
• MP (point to menu bar item)
• B (left-click with mouse button)
• MP (point to menu item)
• B (left-click with mouse button)

Rule 0b Pselects command
Rule 0b Pselects command
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Step 3 MS Windows Menu - Delete Ms

• H (get hand on mouse)
• MP (point to menu bar item)
• B (left-click with mouse button)
• MP (point to menu item)
• B (left-click with mouse button)

Rule 1 Manticipated by P
Keep M
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Step 4 MS Windows Menu Calculate Time

• H (get hand on mouse)
• P (point to menu bar item)
• B (left-click with mouse button)
• MP (point to menu item)
• B (left-click with mouse button)
• Textbook timings (all in seconds)
• H 0.40, P 1.10, B 0.20, M 1.35
• H, 2P, 2B, 1 M
• Total predicted time 4.35 sec

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Macintosh Menu Selection

• Operator sequence
• H(mouse)P(to menu item)B(down)PB(up)
• Now place Ms
• H(mouse)MP(to menu item)B(down)MPB(up)
• Selectively remove Ms
• H(mouse)MP(to menu item)B(down)MPB(up)
• Textbook timings (all in seconds)
• H 0.40, P 1.10, B 0.10 for up or down, M
  1.35
• H, 2P, 2 B, 1 M
• Total predicted time 4.15 sec
• Macintosh is predicted to be .2 secs faster than
  MS Windows, about 5

Rule 0b
Rule 0b
Rule 1 Delete H anticipates P
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Using KLM

• Skilled users
• Performing routine tasks
• The user has done it many times before
• No real learning going on
• Some modest thinking as captured by Ms
• Rules for placing Ms are heuristics
• Best use is for comparing alternatives
• Sometimes predictions are off
• But rankings of faster - slower tend to be
  accurate

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Issues with GOMS family

• What limitations do you see?

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Project time?
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Upcoming

• No class Monday
• Project Part 1 due Wednesday
• DOET 3-4
• Description of Part 2