Learning as a Function of Time

Measures of instructional time are grouped into four ranges-years, days, hours, and minutes-and the strength of the association to outcomes is reviewed within each grouping. Time predicts learning outcomes at a modest level in most of the research, but with exceptions. The use of composite or precise indicators of time-on-task and the use of content-specific outcome measures seem to strengthen the correlational evidence. Complexities such as diminishing returns, the existence of optimum amounts of time, the proper unit of analysis, and the question of causality imply that true experimental designs would clarify the nature of the relationship. The need to include time as one factor in a theory of educational productivity is presented.