M. David Merrill (Marriner David Merill) is an education researcher specializing in instructional design and technology.
Merrill's Component Display Theory (CDT) (1983) describes the micro elements of instruction (single ideas and methods for teaching them). It is designed to work in conjunction with Reigeluth's theory.
CDT is comprised of three parts:
Merrill further classifies learning into two dimensions:
By forming a matrix using the two dimensions of content and performance, the instructor determines which elements on the matrix are the goals for the learner:
The theory also identifies four primary presentation forms:
And some secondary presentation forms:
The matrix is set up to determine the level of performance needed for an area of content. For each of the categories in the matrix, it can be assumed in CRT that there is a combination of primary and secondary presentation forms that will provide the most effective and efficient acquisition of skills and knowledge available. CRT specifies that instruction is more effective when it contains all the necessary primary and secondary forms. Thus, a complete lesson would consist of an objective, followed by some combination of rules, examples, recall, practice, feedback, helps, and mnemonics appropriate to the subject matter and learning task.
The theory is primarily designed for use by groups of learners. Several components are provided so that a wide variety of learners may participate, however each learner only needs the components which specifically work for her to achieve the goals of instruction.