Data processing: measuring – calibrating – or testing – Measurement system – Performance or efficiency evaluation
Reexamination Certificate
1998-10-13
2001-09-25
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Performance or efficiency evaluation
C345S215000, C345S215000, C707S793000, C707S793000, C707S793000
Reexamination Certificate
active
06295509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the usability of the computer-human interface and, more specifically, to defining and utilizing a method that provides an objective, quantitative measurement of the mental effort expended during manipulation of a computer-human interface.
2. Prior Art
Software systems designed for a general purpose computer provide a component to accomplish the functionality specified for the system and a component to expedite both the declaration of data to the computer and the specification of transformations to these data. Software of this latter component plus the input-output devices employed during communication with the computer will comprise the computer-human interface (CHI). Great effort has been expended by cognitive psychologists and software engineers to investigate cognitive factors involved in designing productive CHI that are easily learned, easily retained, and not prone to error. It is apparent that if an objective, quantitative technique were available for measuring the mental effort while manipulating a computer it would advance our ability to design CHI of high usability. Such a tool would find ready application in the areas of: (1) designing interfaces for new application software, (2) comparing the usability of extant software of equivalent functionality, and (3) the screening of applicants for computer based employment and evaluation of employees engaged in computer based employment.
The review of the current state of the cognitive arts relating to computer-human interface design presented below shows that these arts have not articulated an objective, quantitative technique for measuring the mental effort expended by a user while manipulating a CHI. It will then be shown how the present invention overcomes this failure.
Cognitive Aspects of the Computer-Human Interface
The Goals, Operations, Methods, and Selections (GOMS) model proposed by Card, Moran, and Newell (
The Psychology of Human
-
Computer Interaction,
1983) underpins most research into cognitive aspects of user-computer interaction. GOMS presumes a user employs the computer during a “work session” to attain a goal-oriented activity which GOMS terms the “primary goal.” It is posited that users devolve the primary goal into a set of cognitively comprehensible “sub-goals” that, when individually achieved, accomplish the work session's primary goal. Each sub-goal is achieved when the user correctly performs an appropriate “method” provided by the software designers. A method, in turn, comprises one or more “tasks” which, in their turn, comprise one or more permitted sequences of “physical operations” that accomplish a task. Card, et. al. (op. cit., p. 264) identify the “Key/Button Press”, “Mouse-Point”, “Hand-home”, and “Draw-Straight-Line” as the physical operators provided by input devices of a computer and identify a “mentally prepare” operator that is activated when the user appraises results of prior actions, determines the next sub-goal, and develops an actualization plan. After promulgating heuristics to predict the occurrence of the mental operator within sequences of physical operators, Card, et al. (op. cit. pp.147-161; 167-179; 270-278) appraise whether knowledge of cognitive psychology is sufficiently advanced to permit acceptably accurate predictions of the methods selected and the time required to perform each. Many researchers conclude substantial problems remain.
Olson and Olson (The Growth of Cognitive Modeling in Human-Computer Interaction Since GOMS,
Human
-
Computer Interaction,
1990, pp. 221-265) find that when employed by those skilled with GOMS usage, GOMS provides reasonable predictions of the type and occurrence of physical operator execution but is less successful in predicting mental activity. Observing that an estimated 40% of a work session is expended to comprehend, devolve and resolve the primary goal, Allen and Scerbo (Details of Command-Line Language Keystrokes,
ACM Transactions on Office Information Systems,
1983, pp. 159-178) contend that successful application GOMS requires that the occurrence and duration of each mental operator be accurately predicted. To appraise whether GOMS meets these requirements Allen and Scerbo appraise the Card, et al. heuristics. The heuristics are found on, logical grounds, to contain definitional inconsistencies and, on empirical grounds, to not adequately predict either the occurrence or duration of mental activity.
The Cognitive Complexity Theory (CCT) model proposed by Kieras and Polson (An Approach to the Formal Analysis of User Complexity,
International Journal of Man
-
Machine Studies,
1985, pp, 365-394) provides a relevant extension to the original GOMS model. CCT recasts GOMS to permit appraising the “mental load” of using computer interfaces by incorporating user how-to-do-it knowledge into production rules of the following structure:
NAME: IF( Condition 1 is true AND
: : : :
Condition k is true) THEN
PERFORM (set of specified physical operations)
Under CCT users are presumed to have in memory production rules necessary to accomplish each sub-goal of the primary goal. As external stimuli—exemplified by deciding the next sub-goal or reacting to error—are received they are compared against the set of production rule conditions. Any production rule having its conditions met is performed, thus altering the environment which, in turn, alters the external stimuli. The cycle repeats until the primary goal is attained.
To ascertain learnability of a production rule set Bovair, Kieras, and Polson (The Acquisition of Text Editing Skill: A Production System Analysis,
Human
-
Computer Interaction,
1990, p. 1-48) posit that: (1) it is possible to define individual productions of a production rule set to embody equal knowledge content and (2) given the preceding ability the quantity of knowledge implicit in a rule is a linear function of the time required to learn the production rule set. Based on results of their experiments these authors conclude significant correlation exists between the number of new rules and total learning effort. Karat, Fowler, and Granville (Evaluating User Interface Complexity, in Bullinger and Shackel (eds.)
Human
-
Computer Interaction—INTERACT
'87, 1987, p. 489-495) however contend that while formulation of production rules is not difficult, successful formulation of productions of equal knowledge content is unlikely until an exogenous criterion is available that objectively quantifies such knowledge content. Absence of such a criterion produces a conundrum; namely: the logic of top-down problem decomposition dictates that productions should reflect user mental processes and not be crafted by the researcher to achieve production rule equivalence. Designing for equivalence suggests that production rules are developed to meet the criterion under test in order to test whether the criterion is valid.
The CCT presumption of zero learning load to activate different combinations of productions has been investigated by questioning whether user assimilation of complete production systems is an additive function of the learning time of individual productions. Vossen, Sifter, Ziegler (An Empirical Validation of the Cognitive Complexity Theory with Respect to Text, Graphics and Table Editing, in Bullinger and Shackel (eds.)
Human
-
Computer Interaction—INTERACT
'87, 1987, p. 71-75) justify this concern by presenting experimental evidence showing that learning time is not explained solely by a linear relationship of production rules. These authors conclude there is a burden to learning additional productions even though the new productions are deemed equivalent; a learning burden that can be lowered by increased consistency of interface design. Payne and Green (Task-Action Grammar: the model and its development, in Drapier, Dan (ed.)
Task Analysis for Human
-
Computer Interaction,
1989, pp. 75-107) hypothesize that if productions contain equivalent learning loads, persons employing a sys
Hoff Marc S.
Vo Hien
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