Human Computer Interaction Lecture 23 Cognitive Models

Cognitive Models Cognitive models claim to have some representation of users as they interact with an interface, that is they model some aspects of the user’s: understanding, knowledge, intentions or mental processing. Level of representation differs from technique to technique.

Goals vs. Tasks Goals – intentions what you would like to be true. Goals can be divided into sub-goals. Tasks – actions how to achieve the goal or sub-goals. Task can also be divided into sub-task or smaller tasks(task analysis)

Goal and task hierarchies Mental processing as divide-and-conquer Example: sales report produce report gather data . find book names . . do keywords search of names database . . . … further sub-goals . . filter through names and abstracts by hand . search sales database - further sub-goals layout tables and histograms - further sub-goals write description - further sub-goals

Techniques (Models) Cognitive models are classified as below: Hierarchical models GOMS(Goals, Operators, Methods, Selection) Cognitive Complexity Theory (CCT) Linguistic and grammatical models BNF (Backus-Naur Form) Task-Action Grammar (TAG) Physical and device-level models Keystroke-Level Model Three State Model  

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

GOMS Example-1 GOAL: CLOSE-WINDOW . [select Sub GOAL: USE-MENU-METHOD . MOVE-MOUSE-TO-FILE-MENU . PULL-DOWN-FILE-MENU . CLICK-OVER-CLOSE-OPTION Sub 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

GOMS Example-2 Goal: delete a word in a sentence Method-1 for accomplishing goal of deleting a word using menu option: Step1. Recall that word to be deleted has to be highlighted Step2. Recall that command is “cut” Step3. Recall that the command “cut” is in edit menu Step4. Accomplishing goal of selecting and executing the “cut” command Step5. Return with goal accomplished

GOMS Example-2 Method-2 for accomplishing goal of deleting a word using delete key: Step1. Recall where to position cursor in relation to word to be deleted Step2. Recall which key to delete each letter Step3. Press “delete” key to delete each letter Step4. Return with goal accomplished

GOMS Example-2 Operators to use in above methods: Click mouse Drag cursor over text Select menu Move cursor to command Press keyboard key

GOMS Example-2 Selection Rules to decide which method to use: 1: Delete text mouse and selecting from menu if large amount of text is to be deleted 2: Delete text using delete key if small number of letters are to be deleted

Cognitive Complexity Theory Cognitive complexity is the psychological characteristic or variable that shows how complex or simple the frame and perceptual skill of a person are. It is the extent to which a person differentiates and integrates an event. Two parallel descriptions: User production rules Device generalised transition networks Production rules are of the form: if condition then action