Instructional Development Timeline
M. D. Merrill

Component Display Theory (M.D. Merrill)


Component Display Theory (CDT) classifies learning along two dimensions: content (facts, concepts, procedures, and principles) and performance (remembering, using, generalities). The theory specifies four primary presentation forms: rules (expository presentation of a generality), examples (expository presentation of instances), recall (inquisitory generality) and practice (inquisitory instance). Secondary presentation forms include: prerequisites, objectives, helps, mnemonics, and feedback.

The theory specifies that instruction is more effective to the extent that it contains all necessary primary and secondary forms. Thus, a complete lesson would consist of objective followed by some combination of rules, examples, recall, practice, feedback, helps and mnemonics appropriate to the subject matter and learning task. Indeed, the theory suggests that for a given objective and learner, there is a unique combination of presentation forms that results in the most effective learning experience.

Merrill (1983) explains the assumptions about cognition that underlie CDT. While acknowledging a number of different types of memory, Merrill claims that associative and algorithmic memory structures are directly related to the performance components of Remember and Use/Find respectively. Associative memory is a hierarchial network structure; algorithmic memory consists of schema or rules. The distinction between Use and Find performances in algorithmic memory is the use of existing schema to process input versus creating a new schema through reorganization of existing rules.

A significant aspect of the CDT framework is learner control, i.e., the idea that learners can select their own instructional strategies in terms of content and presentation components. In this sense, instruction designed according to CDT provides a high degree of individualization since students can adapt learning to meet their own preferences and styles.

In recent years, Merrill has presented a new version of CDT called Component Design Theory (Merrill, 1994). This new version has a more macro focus than the original theory with the emphasis on course structures (instead of lessons) and instructional transactions rather than presentation forms. In addition, advisor strategies have taken the place of learner control strategies. Development of the new CDT theory has been closely related to work on expert systems and authoring tools for instructional design (e.g., Li & Merrill, 1991; Merrill, Li, & Jones, 1991)


CDT specifies how to design instruction for any cognitive domain. CDT provided the basis for the lesson design in the TICCIT computer based learning system (Merrill, 1980). It also was the basis for the Instructional Quality Profile, a quality control tool for instructional materials (Merrill, Reigeluth & Faust, 1979).


If we were designing a complete lesson on equilateral triangles according to CDT, it would have the following minimum components:

  • Objective - Define an equilateral triangle (Remember-Use)
  • Generality - Definition (attributes, relationships)
  • Instance - Examples (attributes present, representations)
  • Generality Practice - State definition
  • Instance Practice - Classify (attributes present)
  • Feedback - Correct generalities/instances
  • Elaborations - Helps, Prerequisities, Context

If the generality was presented by an explanation or illustration, followed by practice examples, this would be an expository strategy (EG,Eeg). On the other hand, if the students were required to discover the generality on the basis of practice examples, this would be an inquisitory strategy (IG, Ieg).


1. Instruction will be more effective if all three primary performance forms (remember, use, generality) are present.

2. Primary forms can be presented by either an explanatory or inquisitory learning strategy

3. The sequence of primary forms is not critical provided they are all present.

4. Students should be given control over the number of instances or practice items they receive.


Li, Z. & Merrill, M.D. (1991). ID Expert 2.0: Design theory and process. Educational Technology Research & Development, 39(2), 53-69.

Merrill, M.D. (1980). Learner control in computer based learning. Computers and Education, 4, 77-95.

Merrill, M.D. (1983). Component Display Theory. In C. Reigeluth (ed.), Instructional Design Theories and Models. Hillsdale, NJ: Erlbaum Associates.

Merrill, M.D. (1987). A lesson based upon Component Display Theory. In C. Reigeluth (ed.), Instructional Design Theories in Action. Hillsdale, NJ: Erlbaum Associates.

Merrill, M.D. (1994). Instructional Design Theory. Englewood Cliffs, NJ: Educational Technology Publications.

Merrill, M.D., Li, Z. & Jones, M. (1991). Instructional transaction theory: An introduction. Educational Technology, 31(6), 7-12.

Merrill, M.D., Reigeluth, C., & Faust, G. (1979). The instructional quality profile: Curriculum evaluation and design tool. In H. O'Neil (ed.), Procedures for Instructional Systems Development. New York: Academic Press.

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