Human performance modeling: Difference between revisions

Revision as of 13:28, 25 April 2017

Revision as of 16:21, 6 August 2017

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==== Pointing ====

Pointing at stationary targets such as buttons, windows, images, menu items, and controls on computer displays is commonplace and has a well-established modeling tool for analysis - [[Fitts's law|Fitt's law]] (Fitts, 1954) - which states that the time to make an aimed movement (MT) is a linear function of the index of difficulty of the movement: '''''MT = a + bID'''''. The index of difficulty (ID) for any given movement is a function of the ratio of distance to the target (D) and width of the target (W): '''''ID =''''' '''log₂''(2D/W) -''''' a relationship derivable from [[information theory]].<ref name=":1" /> Fitt's law is actually responsible for the ubiquity of the computer [[Mouse (computing)|mouse]], due to the research of Card, English, and Burr (1978). Extensions of Fitt's law also apply to pointing at spatially moving targets, via the ''[[steering law]]'' , originally discovered by C.G. Drury in 1971<ref>{{Cite journal|last=DRURY|first=C. G.|date=1971-03-01|title=Movements with Lateral Constraint|url=http://dx.doi.org/10.1080/00140137108931246|journal=Ergonomics|volume=14|issue=2|pages=293–305|doi=10.1080/00140137108931246|issn=0014-0139|pmid=5093722}}</ref><ref>{{Cite journal|last=Drury|first=C. G.|last2=Daniels|first2=E. B.|date=1975-07-01|title=Performance Limitations in Laterally Constrained Movements|url=http://dx.doi.org/10.1080/00140137508931472|journal=Ergonomics|volume=18|issue=4|pages=389–395|doi=10.1080/00140137508931472|issn=0014-0139}}</ref><ref>{{Cite web|url=http://ieeexplore.ieee.org/abstract/document/4309061/?reload=true|title=Self-Paced Path Control as an Optimization Task - IEEE Xplore Document|website=ieeexplore.ieee.org|language=en-US|access-date=2017-03-02}}</ref> and later on rediscovered in the context of human-computer interaction by Accott & Zhai (1997, 1999).<ref>{{Cite journal|last=Accot|first=Johnny|last2=Zhai|first2=Shumin|date=1997-01-01|title=Beyond Fitts' Law: Models for Trajectory-based HCI Tasks|url=http://doi.acm.org/10.1145/258549.258760|journal=Proceedings of the ACM SIGCHI Conference on Human Factors in Computing Systems|series=CHI '97|___location=New York, NY, USA|publisher=ACM|pages=295–302|doi=10.1145/258549.258760|isbn=0897918029}}</ref><ref>{{Cite journal|last=Accot|first=Johnny|last2=Zhai|first2=Shumin|date=1999-01-01|title=Performance Evaluation of Input Devices in Trajectory-based Tasks: An Application of the Steering Law|url=http://doi.acm.org/10.1145/302979.303133|journal=Proceedings of the SIGCHI Conference on Human Factors in Computing Systems|series=CHI '99|___location=New York, NY, USA|publisher=ACM|pages=466–472|doi=10.1145/302979.303133|isbn=0201485591}}</ref>

==== [[Control theory|Manual Control Theory]] ====

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One area of memory and cognition regards modeling routine cognitive skills; when an operator has the correct knowledge of how to perform a task and simply needs to execute that knowledge. This is widely applicable, as many operators are practiced enough that their procedures become routine. The GOMS (goals, operators, methods, and selection rules) family of Human Performance Models popularized and well-defined by researchers in the field (Card et al., 1983; John & Kieras, 1996a, 1996b) were originally applied to model users of computer interfaces, but have since been extended to other areas. They are useful HPM tools, suitable for a variety of different concerns and sizes of analysis, but are limited in regard to analyzing user error (see Wood & Kieras, 2002, for an effort to extend GOMS to handling errors).<ref name=":1" />

The simplest form of a GOMS model is a ''keystroke-level model'' (KLM) - in which all physical actions are listed (e,.g., keystrokes, mouse clicks), also termed operations, that a user must take in order to complete a given task. Mental operations (e.g., find an object on the screen) augment this using a straightforward set of rules. Each operations has a time associated with it (such as 280 ms for a keystroke), and the total time for the task is estimated by adding up operation times. The efficiency of two procedures may then be compared, using their respected estimated execution times. Although this form of model is highly approximate (many assumptions are taken at liberty), it is a form of model still used today (e.g., in-vehicle information systems and mobile phones).<ref name=":1" />

Detailed versions of GOMS exist, including:

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=== Abstraction ===

The abstraction necessary for understandable models competes with accuracy. While generality, simplicity, and understandability are important to the application of models in human factors practice, many valuable human performance models are inaccessible to those without graduate, or postdoctoral training. For example, while [[Fitts's law]] is straightforward for even undergraduates, the lens model requires an intimate understanding of multiple regression, and construction of an ACT-R type model requires extensive programming skills and years of experience. While the successes of complex models are considerable, a practitioner of HPM must be aware of the trade-offs between accuracy and usability.<ref name=":1" />

=== Free Parameters ===