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Design Models Reference

March 20, 2009

As in the previous post Mental Models (conceptual models) (user’s model) this post will document the discourse upon what Cooper et al refers to as Represented Models and what Norman calls Designer’s Models. The same two writers’ definitions will be listed here for future reference and analysis. Implementation models will be discussed at a later stage separately as my project research focus is on mental and designer’s models.
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NORMAN, D.A. (1983) Some observations on Mental Models. In D. GENTNER, and A.L. STEVENS, eds. Mental Models. Lawrence Erlbaum Associates Inc. pp7-14

RE: The System Image
In the ideal world, when a system is constructed, the design will be based around a conceptual model. This conceptual model should govern the entire human interface with the system, so that the image of that system seen by the user is consistent, cohesive, and intelligible. I call this image the system image to distinguish it from the conceptual model upon which it is based, and the mental model one hopes the user will form of the system. (…) if the system image is consistent with that [underlying conceptual model to the user] model, the user’s mental model will also be consistent.” (p13)

Our conceptualization of a target sytem should not be confused with a mental model that a user creates of that system. The designer’s conceptualization may also differ from the image that the system itself presents to the user. In the ideal world, the system image will be consistent with the designer’s conceptualization, and the user’smental model will thereby be consistent with both.” (p14)

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YOUNG, R.M. (1983) Surrogates and Mappings: Two Kinds of Conceptual Models for Interactive Devices. In D. GENTNER, and A.L. STEVENS, eds. Mental Models. Lawrence Erlbaum Associates Inc. pp35-52

RE: User’s Conceptual Model (UCM)
Is the purpose of the UCM [ ”user’s conceptual model”]to help the User employ the device more easily and effectively, or to help the Psychologist make better predictions of the User’s behaviour? Although these aims are not necessarily contradictory, we have to allow the possibility that their differing requirements will shape the UCM in different ways. Whether the Designer can, or should, share the same UCM as the Psychologist (or the User) is at present unclear. One can argue that the Designer should be encouraged to do so in order to achieve a satisfactory interface design. Alternatively, one can believe that that for the model to remain tractable, the Designer will need to employ a cruder UCM which incorporates assumptions about the tasks to be tackled and the methods to be employed in a way which invalidates it as a psychological model. At present we simply do not understand the issues well enough or have enough evidence to choose between these opposed views. Indeed, the formulation of the question in these terms is itself quite new.” (pp36-37)

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Taken from: About Face 3
COOPER, A., REIMAN, R. and CRONIN, D. (2007) About Face 3: The Essentials of Interaction Design. Indianapolis: Wiley Publishing Inc.

[The] “ability to represent the computer’s functioning independent of its true actions is far more pronounced in software than in any other medium. It allows a clever designer to hide some of the more unsavoury facts of how the software is really getting the job done. This disconnection between what is implemented and what is offered as an explanation gives rise to a third model in the digital world, the designer’s represented model – the way the designers chooses to represent a program’s functioning to the user. Donald Norman refers to this simply as the designer’s model. (…) In the world of software, a program’s represented model can (and often should) be quite different from the actual processing structure of the program. (…) This concept of the represented model has no widespread counterpart in the mechanical world. (…) The closer the represented model comes to the user’s mental model, the easier he will find the program to use and to understand. Generally, offering a represented model that follows the implementation model too closely significantly reduces the user’s ability to learn and use the program.” (p29)

One of the most important goals of the designer should be to make the represented model match the mental model of users as closely as possible.” (p30)

Intelligent people always learn better when they understand cause and effect, so you must give them an understanding of why things work as they do. We use mental models to bridge the contradiction. If the represented model of the interface closely follows the user’s mental model it will provide the understanding the user needs without forcing him to figure out the implementation model.” (p46)

It’s absolutely critical that the represented model of the interface – how the design behaves and presents itself – should match the user’s mental model as closely as possible, rather than reflecting the implementation model of how the product is actually constructed internally. In order to accomplish this, we must formally record these expectations. (attitudes, experiences, aspirations – social, cultural, environmental, cognitive factors that influence expectations).” (p118)

Everything a user does is something he or she considers to be valid and reasonable. Most people don’t like to admit to mistakes in their own minds, so the program shouldn’t contradict this mindset in its interactions with users.” (p336)

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Taken from: The Design of Everyday Things
NORMAN, D.A. (1998) The Design of Everyday Things. MIT Press

In his book Norman is discussing product design but his observations can be equally applied to digital products.

The design model is the designer’s conceptual model. (…) The designer expects the user’s model to be identical to the design model. But the designer doesn’t talk directly to the user – all communication takes place through the system image. If the system image does not make the design model clear and consistent, then the user will end up with the wrong mental model.” (p16)

Designers should provide users with appropriate models when they are not supplied, people are likely to make up inappropriate ones.” (p70)

The design model is the conceptualization that the designer has in mind. The user’s model is what the user develops to explain the operation of the system. Ideally, the user’s model and the design model are equivalent. However the user and designer communicate only through the system itself: its physical appearance, its operation, the way it responds, and the manuals and instructions that accompany it. Thus the system image is critical: the designer must ensure that everything about the product is consistent with and exemplifies the operation of the proper conceptual model. ” (pp189-190)


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