"Instructional Design (also called Instructional Systems Design (ISD)) is the practice of creating "instructional experiences which make the acquisition of knowledge and skill more efficient, effective, and appealing." Merrill, Drake, Lacy, and Pratt, 1996)
“The process consists broadly of determining the current state and needs of the learner, defining the end goal of instruction, and creating some "intervention" to assist in the transition. Ideally the process is informed by pedagogically (process of teaching) and andragogically (adult learning) tested theories of learning and may take place in student-only, teacher-led or community-based settings”. (Duffy, and Cunningham, 1996)
“The outcome of this instruction may be directly observable and scientifically measured or completely hidden and assumed. There are many instructional design models but many are based on the ADDIE model with the five phases: 1) analysis, 2) design, 3) development, 4) implementation, and 5) evaluation. As a field, instructional design is historically and traditionally rooted in cognitive and behavioral psychology, though recently Constructivism (learning theory) has influenced thinking in the field.” (Duffy, Cunningham and Jonassen,1992-1996).
Merrill, M. D., Drake, L., Lacy, M. J., Pratt, J., & ID2_Research_Group. (1996). Reclaiming instructional design. Educational Technology, 36(5), 5-7. http://mdavidmerrill.com/Papers/Reclaiming.PDF
Cognition and instruction: Their historic meeting within educational psychology. Mayer, Richard E. Journal of Educational Psychology, Vol 84(4), Dec 1992, 405-412. doi:10.1037/0022-0622.214.171.1245 http://psycnet.apa.org/journals/edu/84/4/405/
Duffy, T. M., & Cunningham, D. J. (1996). Constructivism: Implications for the design and delivery of instruction. In D. Jonassen (Ed.), Handbook of Research for Educational Communications and Technology (pp. 170-198). New York: Simon & Schuster Macmillan
Duffy, T. M. , & Jonassen, D. H. (1992). Constructivism: New implications for instructional technology. In T. Duffy & D. Jonassen (Eds.), Constructivism and the technology of instruction (pp. 1-16). Hillsdale, NJ: Erlbaum.