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  During WWII, a large number of psychologist and educator who had training and experience in conducting experimental research were called upon to conduct research and development training materials for the military services.
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  This allowed instructional designers to measure the amount of knowledge acquired as a result of instruction.
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  Led to the notion that learners should acquire lower level skills before they attempt higher level ones.
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  Many began producing computer based instruction. Computers began to be used to automate some instructional design task.
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  Since the beginning of the twenty-first century, the increased use of the internet has led to utilizing it as a means of providing instruction to learners through online courses and a variety of other means.