The field of instructional design developed in the 1960s and early 1970s at a time when behaviorism still dominated mainstream psychology. ID shared those behaviorist roots and at the time was closer to mainstream psychology in the U. S. ID theorists such as Gagné, Briggs, Merrill, and Scandura all were educational psychologists. With the cognitive revolution of the 1970s, instructional psychology differentiated itself from ID and drifted more to the cognitive mainstream, leaving ID relatively isolated with concerns of design. In a review of instructional psychology in 1981, Lauren Resnick (who only a few years earlier had developed Gagné-style learning hierarchies) observed: