Student Instruction Should Be Distributed Over Long Time Periods

In many academic courses, students encounter a particular fact or concept many times over a period of a few weeks and then do not see it again during the remainder of the course. Are these brief instructional periods sufficient, or should the same amount of instruction be distributed over longer periods of time? This question was the focus of several recent studies in which a fixed amount of instruction was distributed over time periods of varying duration and followed by a delayed posttest. With few exceptions, the results showed that longer instructional periods produced greater posttest scores if the posttest was delayed by at least a month or so. Notably, the search criteria for this review excluded several oft-cited studies favoring short foreign language courses over longer ones, but a closer look at these studies reveals limitations (e.g., no delayed posttest or confounding variables). In brief, the best reading of the data is that long-term learning is best achieved when the exposures to a concept are distributed over time periods that are longer rather than shorter.