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Merrill’s Pebble-in-the Pond instructional design model focuses primarily on the design phase of the whole instructional development process most commonly referred to as ADDIE. It aims to implement his pedagogically oriented First Principles of Instruction and is based on the idea of successive approximations or cyclical iterations which have a lot in common with agile project management methods such as Scrum. It is also closely related to the whole problem 4C/ID instructional design model advocated by van Merriënboer and Kirschner. Although primarily designed for digital and online learning the Pebble model can also be used to design face-to-face teaching.

Critique of Instructional Design models

The main criticisms of instructional design models are that they are too linear, inflexible and time-consuming and often fail to design effective learning (Gordon & Zemke, 2000). The linear critique has been addressed to some extent by Michael Allen’s Successive Approximation Model (SAM). Merrill offers two additional criticism of traditional ADDIE approaches:

  1. The early specification of instructional objectives which are abstract representations of the knowledge to be taught rather than the knowledge itself lead to translation errors (learning activities and resources which do not align to the objectives).
  2. Abstract descriptions of the learning content and instructional strategies in design documents, storyboards and templates also lead to translation errors.

Wiggins and McTighe (2011) advocate an approach they term ‘backwards design’ which is similar to Merrill’s approach. Their approach also starts with learners’ performance after learning and teaching rather than abstract objectives.

Pebble-in-the-pond instructional design model

The Pebble model assumes a high-level goal, but not detailed objectives and starts from a representation of a whole problem or task which learners will be able to solve or execute following the instruction. This problem-centred approach is very different from many academic courses in UK higher education which provide information-heavy teaching but limited opportunities for application. Merrill advocates working with content (in the form of problems) early on in the instructional design process. Once the problem and related content are identified, then the instructional strategies, learner interactions and assessments are developed in the form of functioning prototypes rather than abstract and descriptive design documents.

Early problems in the progression are demonstrated to learners and as they progress through the problem sequence they are required to engage with more components of the problem and guidance is faded out. Merrill advocates designing a demonstration learning event for the first one or two problems; designing a combination of demonstration and learner application learning events for the next one or two problems and finally designing application for the remaining problems in the sequence. The model concludes with a functional prototype that serves as a specification for the production, implementation, and summative evaluation of the final version.

Pebble in the pond diagram

  1. Identify a problem
  2. The learning design process begins with identifying an instance of a structured or ill-structured real-world problem which learners will learn to solve, rather than with an abstract description of the problem and its solution. Designing an actual portrayal of the problem and a demonstration of its solution is less ambiguous than giving learners an abstract description of the problem. The result of this stage is a functional prototype with demonstration instructional events which show learners the consequence, conditions, and steps required for an instance of the problem.

  3. Design a progression of problems
  4. The second stage involves designing a series of increasingly complex problems that gradually increase in complexity, difficulty, or the number of component skills required to complete the task. Only one or two new components should be introduced for each new problem portrayal. This approach is based on Reigeluth’s Elaboration Theory.

    A skills complexity analysis is a procedure which can be used for sequencing the progression of portrayals from simple to complex determined by the number and type of conditions and steps required for each consequence in the problem progression. The result of this stage is a functional prototype with demonstration and application learning events for each portrayal in the progression which covers all of the integral component skills.

  5. Design instruction for component skills
  6. Next, the component skills specifically required to solve the problem should be identified and reviewed to ensure that, by solving each problem in the progression, learners will acquire all of the intended knowledge and skill required to meet the instructional goals. The result of this stage is a functional prototype with demonstration and application learning events for each component skill.

  7. Design instructional strategy enhancements
  8. (a) Design a structural framework for the problems in the progression. For Merrill, a structural framework is an organisation of previously learned information that learners can use to adapt an existing mental model or to build a new mental model for new content. Examples of structural frameworks include mnemonics, analogies, metaphors and checklists.

    (b) Design opportunities for peer collaboration and critique which help learners to acquire skills and to integrate their new knowledge by being required to reflect on, discuss, or defend their new knowledge or skill.

  9. Finalise the instructional design
  10. Design an appropriate interface, navigation and supporting resources for your functional prototype ready for evaluation, production, and implementation.

  11. Design evaluation

The final stage is to design an evaluation which involves data collection, formative evaluation and prototype revision.


There are four key properties of Merrill’s Pebble instructional design model:

  1. Oriented around learning principles (First Principles of Instruction) rather than oriented around steps in a traditional instructional design process such as ADDIE.
  2. A content-first approach as it uses the actual learning materials as the primary vehicle for designing learning rather than descriptions of the materials. The content needed for learning is identified near the start of the process, then teacher demonstrations and learner activities are designed and developed.
  3. A problem-centred approach as the learning and teaching activities are embedded in the context of problems to be solved rather than as a set of skills that will eventually be used to solve a problem toward the end of the learning sequence. Seeing a portrayal of an actual problem or task execution and a demonstration of its solution or execution is far more easily understood by learners than an abstract statement (learning outcomes) describing the problem or task.
  4. An iterative prototyping approach as a functional prototype of the learning is the primary design product rather than an abstract design specification. Both instructional designers and learners can see what the learning looks like, the instructional activities, assessment interactions and the interface. Rapidly iterating a prototype also has the advantage of not having to constantly update design specifications which in any case only describe the desired design changes. Lastly, working on a prototype enables formative evaluation by learners which provides valuable feedback which can be used to improve the design before it is implemented in its final form.

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Allen, M. (2012). Agile eLearning Development with SAM | Allen Interactions. Retrieved 8 August 2019, from Allen Interactions website: https://www.alleninteractions.com/sam-process

Clark, D. (2015). History of the ADDIE Model. Retrieved 8 August 2019, from http://www.nwlink.com/~donclark/history_isd/addie.html

Gordon, J., & Zemke, R. (2000). The attack on ISD. Training, 37, 43–53. Retrieved 8 August 2019, https://performancexdesign.files.wordpress.com/2011/03/gordon_attack-on-isd.pdf

Kirschner, P., & Neelen, M. (2018, March 20). Complex skills in the workplace and what it means to design for them. Retrieved 6 August 2019, from 3-Star learning experiences website: https://3starlearningexperiences.wordpress.com/2018/03/20/complex-skills-in-the-workplace-and-what-it-means-to-design-for-them/

Merriënboer, J. J. G. V., & Kirschner, P. A. (2018). 4CID.org – About 4C/ID. Retrieved 6 August 2019, from Four-Component Instructional Design (4C/ID) website: https://sites.google.com/view/4cid/about-4cid

Merrill, M. D. (2013). Pebble-in-the-Pond Instructional Design. Retrieved 6 August 2019, from https://www.youtube.com/watch?reload=9&v=SUg2u_v56l0

Potter, K. (n.d.). Formative Evaluation. Retrieved 8 August 2019, from Applied Theories of ID website: https://www.itma.vt.edu/courses/appliedid/lesson_10.php

Reigeluth, C. (n.d.). Elaboration Theory. Retrieved 7 March 2019, from InstructionalDesign.org website: https://www.instructionaldesign.org/theories/elaboration-theory/

Rimmer, T. (2016). An Introduction to SAM for Instructional Designers. Retrieved 8 August 2019, from E-Learning Heroes website: https://community.articulate.com/articles/an-introduction-to-sam-for-instructional-designers

What is Scrum? (n.d.). Retrieved 13 August 2019, from Scrum.org website: https://www.scrum.org/resources/what-is-scrum

Wiggins, G., & McTighe, J. (2011). The Understanding by Design Guide to Creating High-Quality Units. Alexandria, United States: Association for Supervision & Curriculum Development.

Posted by Thomas H

Learning technologist at the University of London. Interested in Instructional Design, Learning Design, Multimedia Learning, Educational Research, and Open Education. Follow @myBRAIN_isOPEN

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