Abstract
Two approaches to word learning were investigated in 1214 6th- to 12th-grade students. Definitions were provided, followed either by two sentences that were semantically correct exemplars, called semantic reinforcement learning, or by one correct sentence and a contrasting incorrect sentence (i.e., example followed by a structurally aligned non-example), called semantic discrimination learning. Type of learning was blocked, and examples and non-examples were explained. Effects of affix frequency were also assessed. Students were taught words, followed by assessments of abilities to recall the meanings of the words immediately after learning them, to choose the correct words among distractors to match given definitions after all words had been instructed, and to judge the semantic veracity of new sentences containing taught words 1-3 days later. Explanatory item response models were used to predict word learning using student and item characteristics along with their interactions. Few grade-related differences emerged. Higher-frequency affixes were generally beneficial for learning and retention across comprehension skill levels and measures. Immediate recall of word meanings was facilitated by semantic reinforcement learning. In contrast, performance after all the words had been instructed was facilitated by semantic discrimination learning, but only for more highly skilled comprehenders. The ability to learn the meanings of new words accounted for unique variance on one measure of reading comprehension, controlling for decoding, previously acquired vocabulary knowledge, and working memory. Results are discussed with reference to models of vocabulary learning and implications for vocabulary instruction for adolescents.