Abstract
When to teach technical terms in content area classes to maximize learning of their meanings was studied using 36 ninth-grade biology classes, 12 twelfth-grade government classes, and 12 twelfth-grade economics classes assigned randomly by subject area to one of three treatment conditions: (1) vocabulary instruction before reading, (2)glossary available during reading, or (3) vocabulary instruction after reading. The teacher of each class used investigator-constructed materials to teach 11 terms from a chapter in the assigned textbook while continuing to provide regular instruction related to the chapter. The materials of the “before” and “after” groups differed from those of the “during” group primarily by being presented with an overhead projector rather than on paper. Learning was assessed by requiring the students to write each definition when cued solely by the term itself. Posttest raw scores were converted to z-scores within each subject area, and z-scores of class means were used in four main analyses of variance—one involving all 60 classes, two focusing on one grade level at a time, and one involving nine sets of 3 classes taught by the same teacher. No significant differences attributable to the time of instruction were found. Further analyses with student as the unit of analysis revealed a strong teacher effect. The main conclusion drawn was that, if the objective is the learning of definitions, the manner in which a content area teacher delivers vocabulary instruction is more important than when it is delivered.