[1] PSI was conceived of as an application of Skinner's theories of learning, grounded in operant conditioning strategies of behaviorism.
[4] The Keller Plan has mainly been used in higher education, particularly as a more personalized form of instruction in large classes, but there is nothing inherent in Keller's formulation to restrict its application to particular grade levels, content, or types of courses;[4] for instance the papers [5] and [6] report on usage in elementary school and junior high school, respectively.
Education is still dominated by "same pace, different learning" approaches, and the number of new research publications about PSI gradually declined after its heyday in the 70's.
[4] Several possible reasons are given for this, not the least that PSI represented a too radical deviation from established teaching practices and educational management routines.
[12] However, it has been speculated that PSI might see a revival with modern educational technology, as information technology could gradually alleviate teacher burdens related to frequent testing and feedback, as well as mitigate the increased administrative complexity that courses with student self-pacing have over those with instructor-set pace.