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In 1993, Tessmer and Wedman conducted a study that was validated two years later by Winer and Vasquez and "both studies confirmed that instructional designers use ID models, but not in their entirety nor exclusively" (Vannoy, 2008, p. 14).

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MED-542 (1996, October). Staff Development Slide Shows: Curriculum and Instruction [online]. Retrieved from http://207.87.31.133/med-54/MED542.htm

Tessmer, M., & Wedman, J. F. (1990). A layers-of-necessity instructional development model. Educational Technology Research and Development, 38(2), 77-85.

Vannoy, K. E. H. (2008, June). Instructional design using course management systems (Doctoral dissertation, Capella University, 2008). Retrieved May 26, 2016, from https://books.google.com/books?id=Ekkms4pY5EwC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false. (UMI No. 3310887)

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The US Military uses Layers-of-necessity as a model for its training programs, specifically for training medical technicians in the Navy (MED-542, 1996).

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Due to time and resources limitations, one of the caveats of this method is that instructional designers have to develop the “good enough for now” attitude (p. 78).

Tessmer and Wedman acknowledge the disadvantages of their model when they write that “in-depth subskills analysis, objectives writing, and test development are not conducted unless additional time and resources are available” (p. 82). New materials are only developed if time allows. The faster-cheaper-(better?) mentality may not serve students appropriately if resources are so scarce that proper materials are not able to be generated.

This model is not complete - it essentially serves as a resource to let instructional designers into the reality of our world. What is the best may not always be practical, so instructional designers should do their best with what they have.

With less planning and objectives, there may be gaps in the knowledge acquired by participants in the training program/students in the classroom.

This model should not be independent of other learning models. Other learning models, such as ADDIE, should be considered by instructional designers to ensure that important components are not omitted.

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Layers-of-necessity is a very practical learning theory. Tessmer & Wedman (1990) write that “instruction evolves over time rather than emerges fully developed, the model offers an alternative means of achieving quality instruction” (p. 77).

Instructional designers do not have to wait until their project is fully developed before implementing it. In this model, as time and resources improve, the instructional designer can add more layers as appropriate.

This learning theory is applicable to an instructional designer in any field (from industry to K-12).

Unlike other learning theories, there are optional steps. As Tessmer and Wedman write “[in other theories], each component is fully executed. No component has a ‘good enough for now’ indicator that adjusts to the exigencies of time and resources” (p. 78).

This theory is customizable. The instructional designer chooses a layer that is “matched to the necessities of the project” (p. 79).

Layering allows instructional designers to revisit earlier material and add to it to enhance instruction, versus other models that advocate for closure of components.

Project components can be reduced based on project limitations, without the stress of failure.

Tessmer and Wedman write that layers-of-necessity is a “cost-benefit approach to design: select activities that are likely to have the greatest instructional benefit for the least resource/time costs” (p. 81).

Effectiveness activities are based on what can be done as opposed to what theoretically should be done.

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Layers of necessity can be used in just about any context due to its adaptability. Instead of ID processes being presented sequentially phase-by-phase, different processes are clustered together in “layers,” with the bare necessities comprising Layer 1 and more complex and in-depth processes comprising each subsequent layer.

When facing significant constraints on time and/or resources, IDers may choose to use Layer 1, which includes the bare necessities of situational assessment, goal analysis, instructional strategy development, materials development, and evaluation & revision (Tessmer & Wedman, 1990, p. 82). If there are fewer constraints on time and/or resources, IDers may choose to move on to the next layers, adding a higher level of depth and complexity to the end product.

Layers of Necessity can be used in any setting whether corporate, K-12, higher education, government, non-profit, etc., as it is not specific to any particular field. Tessmer and Wedman (1990) explain, “In many respects the layers-of-necessity model is not a new model but rather a new approach to using existing (and presumed familiar) models and strategies in an integrated, practical manner” (p. 84).

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Published in Educational technology research and development in May 1990

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Martin Tessmer, Associate Professor of ID at University of Colorado at Denver

John F. Wedman, Associate Professor of Educational Technology, University of Missouri

Layers-of-necessity was developed following the need for a more practical ID model that could be adapted to various contexts and constraints. Tessmer and Wedman examined Dick & Carey’s model of ID in depth and developed an alternative that is less lockstep and more customizable to fit different situations. Layers-of-Necessity is considered a “‘practitioner’s model’ of instructional design and development” (Tessmer & Wedman, 1990, p. 78).

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Layers-of-necessity is represented by the chameleon due to its ability to adapt to different contexts with various constraints.