cognitive models Morten Fjeld HCI Course, Spring term 2006 chapter 12 Cognitive models Common assumptions about the architecture of the human mind

Transcription

1 Cognitive models chapter 12 cognitive models 1/42 They model aspects of user: understanding knowledge intentions processing Common categorisation: Competence: What users ideally should do versus Performance: What users actually do 2/42 Common assumptions about the architecture of the human mind Long-term/Short-term memory Problem spaces Interacting Cognitive Subsystems Connectionist Cognitive models 1 Goal and task hierarchies (GOMS, CCT) 2 Linguistic notations (BNF, TAG) 3 Physical and device models (KLM) 4 Automating Inspection Methods (Common assumptions from above are not necessary here) 3/42 4/42 1 Goal and task hierarchies (GOMS, CCT) Granularity Where exactly do we start? Where exactly do we stop? Routine learned behaviour, not problem solving The unit task Conflict More than one way to achieve a goal Error 5/ Goals, Operators, Methods and Selection (GOMS) Goals what the user wants to achieve Operators basic actions user performs Methods decomposition of a goal into subgoals/operators Selection means of choosing between competing methods 6/42 1

2 GOMS example 1.2 Cognitive Complexity Theory (CCT) GOAL: CLOSE-WINDOW. [select GOAL: USE-MENU-METHOD. MOVE-MOUSE-TO-FILE-MENU. PULL-DOWN-FILE-MENU. CLICK-OVER-CLOSE-OPTION GOAL: USE-CTRL-W-METHOD. PRESS-CONTROL-W-KEYS] For a particular user: Rule 1: Select USE-MENU-METHOD unless another rule applies Rule 2: If the application is GAME, select CTRL-W-METHOD 7/42 Two descriptions: User production rules Form: if condition then action (Device generalised transition networks) Example Cognitive model of editing with vi 8/42 CCT example: editing with vi CCT example: editing with vi Why many users like the vi-editor: Vi is available on many platforms; very important for system administrators because they often work on different systems You don't need X or mouse for high efficiency Vi is compact, fully developed, and runs on *any* Unix-system Vi supports syntax highlighting Vi is very well configurable 9/42 10/42 Four rules to model inserting a space Active rules: SELECT-INSERT-SPACE INSERT-SPACE-MOVE-FIRST INSERT-SPACE-DOIT INSERT-SPACE-DONE SELECT-INSERT-SPACE matches current working memory New working memory (GOAL insert space) (NOTE executing insert space) (LINE 5) (COLUMN 23) 2 Linguistic notations Understanding the user's behaviour and cognitive difficulty based on analysis of language between user and system. Similar in emphasis to dialogue models Example Backus Naur Form (BNF) (SELECT-INSERT-SPACE IF (AND (TEST-GOAL perform unit task) (TEST-TEXT task is insert space) (NOT (TEST-GOAL insert space)) (NOT (TEST-NOTE executing insert space))) THEN ( (ADD-GOAL insert space) (ADD-NOTE executing insert space) (LOOK-TEXT task is 11/42 at %LINE %COLUMN))) 12/42 2

3 2.1 Backus-Naur Form (BNF) Very common notation from computer science A purely syntactic view of the dialogue Terminals lowest level of user behaviour e.g. CLICK-MOUSE, MOVE-MOUSE Nonterminals ordering of terminals higher level of abstraction e.g. select-menu, position-mouse Example of BNF Basic syntax: nonterminal ::= expression An expression contains terminals and nonterminals combined in sequence (+) or as alternatives ( ) draw line ::= select line + choose points + last point select line ::= pos mouse + CLICK MOUSE choose points ::= choose one choose one + choose points choose one ::= pos mouse + CLICK MOUSE last point ::= pos mouse + DBL CLICK MOUSE pos mouse ::= NULL MOVE MOUSE+ pos mouse 13/42 14/42 Measurements with BNF Number of rules (not so good) Number of + and operators Complications same syntax for different semantics no reflection of user's perception minimal consistency checking 15/42 Backus-Naur Form (BNF), example Consider this BNF for a US postal address <postal-address> ::= <name-part> <street-address> <zip-part> <personal-part> ::= <name> <initial> ". <name-part> ::= <personal-part> <last-name> [<jr-part>] <EOL> <personal-part> <name-part> <street-address> ::= [<apt>] <house-num> <street-name> <EOL> <zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL> 16/42 Backus-Naur Form (BNF), example <postal-address> ::= <name-part> <street-address> <zip-part> <personal-part> ::= <name> <initial> ". <name-part> ::= <personal-part> <last-name> [<jr-part>] <EOL> <personal-part> <name-part>... This translates into English as "A postal-address consists of a name-part, followed by a street-address part, followed by a zip-code part. A personal-part consists of either a first name or an initial followed by a dot. A name-part consists of either: a personal-part followed by a last name followed by an optional "jr-part" (Jr., Sr., or dynastic number) and end-of-line, or a personal part followed by a name part (recursion in BNFs, covering the case of people who use multiple first and middle names and/or initials). 17/42 Backus-Naur Form (BNF), example... continued: <street-address> ::= [<apt>] <house-num> <street-name> <EOL> <zip-part> ::= <town-name> "," <state-code> <ZIP-code> <EOL> This translates into English as (continued) A street address consists of an optional apartment specifier, followed by a street number, followed by a street name. A zip-part consists of a town-name, followed by a comma, followed by a state code, followed by a ZIP-code followed by an end-of-line." 18/42 3

4 Short exercise 1) Describe a Swedish bank account in text. A Swedish bank account description consist of." 2) Then translate the text into Backus-Naur Form (BNF). Short exercise ENGLISH SWEDISH Bank Name Bankens namn t.ex. Nordea Bank Address Bankens Address Bank City Stad Bank Zip Code Postnummer Bank Country land Bank Phone tel nr. till banken Name on Bank Account Kontos ägare namn Account Number kontonummer Bank Routing No. sorteringskod för banken Check No. kontrollnummer Bank Swift Code Swift kod för banken, 8 el 11 tecken sök på banken eller swifts nätsidor Bank IBAN Code kontonummer i IBANform fås från banken 19/42 20/42 Apropos: Backus-Naur Form (BNF) examples comes from Foldoc 3 Physical and device models The Keystroke Level Model (KLM) Buxton's 3-state model FOLDOC is a searchable dictionary of acronyms, jargon, programming languages, tools, architecture, operating systems, networking, theory, conventions, standards, mathematics, telecoms, electronics, institutions, companies, projects, products, history, in fact anything to do with computing. Based on empirical knowledge of human motor system User's task: acquisition then execution. these only address execution Complementary with goal hierarchies 21/42 22/ Keystroke Level Model (KLM) six execution phase operators Physical motor: K - keystroking P - pointing (use Fitt s Law) H - homing D - drawing Mental M - mental preparation System R -response times are empirically determined. T execute = TK + TP + TH + TD + TM + TR 23/42 Fitt s Law for ann Estimation of Pointing Time T = a + b log2(d/s + 1) D: Distance to target S: Size of target a, b: Empirically estimated constants Original form of Fitt s Law, 1954, without a constant: T = log2(2a/w) 24/42 4

5 Fitt s Law, example 1: Fitt s Law, example 2: Demo application intro page Demo application program Width 40, Height 37 time = 0.0 Width 29, Height 22 time =? Width 63, Height 92 time =? 25/42 26/42 Keystroke Level Model (KLM) 1. Move hand to mouse H[mouse] 2. Position mouse after bad character PB[LEFT] 3. Return to keyboard H[keyboard] 4. Delete character MK[DELETE] 5. Type correction K[char] 6. Reposition insertion point H[mouse]MPB[LEFT] KLM example GOAL: ICONISE-WINDOW [select GOAL: USE-CLOSE-METHOD. MOVE-MOUSE-TO- FILE-MENU. PULL-DOWN-FILE-MENU. CLICK-OVER-CLOSE-OPTION GOAL: USE-CTRL-W-METHOD PRESS-CONTROL-W-KEY] compare alternatives: USE-CTRL-W-METHOD vs. USE-CLOSE-METHOD assume hand starts on mouse USE-CTRL-W-METHOD H[to kbd] 0.40 K[ctrlW key] 0.28 Total 2.03 s USE-CLOSE-METHOD P[to menu] 1.1 B[LEFT down] 0.1 P[to option] 1.1 B[LEFT up] 0.1 Total 3.75 s 27/42 28/42 Exercise: Apply KLM Scenario: -- train ride ends, the user wants to delete all desk-top icons starting with T (temporary). -- Find and delete all icons starting with T -- Two conditions: Pad and Pin Exercise: -- Establish a KLM Model aiming to compare Pad and Pin -- Is clutching an issue for this task? Regarding Train Ride Scenario Touch & Type 29/42 USE-PAD-METHOD USE-PIN-METHOD P[to menu] 1.1 H[to kbd] 0.40 B[LEFT down] 0.1 K[ctrlW key] 0.28 P[to option] 1.1 B[LEFT up] 0.1 Total z.x s Total x.y s 30/42 Fallot-Burghardt, Fjeld, Ziegenspeck, Speirs, Läubli ETH Zurich and FBZS Interface h l 5

6 Typing mode Touch mode Typing mode: both hands type on the keyboard Mouse mode: left hand starts mouse mode by touching the mouse buttons, right hand steers mouse pointer by gliding over the keys (keys are not depressed) 31/42 32/42 Isometric Rate Control vs. Elastic Position Control 6DOF Input Devices SpaceCat Martin Sundin (Ph.D. 2001) Morten Fjeld (discussions & advice) ZIP and IHA, ETH Zurich SpaceBall Space Mouse SpaceCat 33/42 34/42 Product Docking Task 35/42 36/42 6

7 3.2 Buxton's 3-state model Mouse vs. light-pen transitions 3.2 Buxton's 3-state model 37/42 38/ Buxton's 3-state model 4: Automating Inspection Methods -- Analysis Support Web UIs 39/42 40/42 4: Automating Inspection Methods -- Analysis Support Web UIs 4: Automating Inspection Methods But also for what pilots do 41/42 42/42 7