Microcomputers were accepted by schools in the 1980s. Instructional television was used in the early-to-mid 20th century for both educational and wartime purposes. The Educational Television and Radio Center invested $170 million in educational television. Educational psychologist Richard Clark concluded that media are vehicles that deliver instruction but do not influence student achievement. Behaviorism was the dominant pedagogical theory used in the first part of the 20th century. Educational technology is the study and ethical practice of facilitating learning through appropriate use of technology.