App-Based Morphological Training Produces Lasting Effects on Word Knowledge in Primary School Children: A Randomized Controlled Trial

Morphemes, the smallest meaning-bearing units of language, recur in many words. Therefore, morphological knowledge can facilitate the comprehension of novel words. This study tested the effectiveness of a morphological training program on children's learning and retention of exposed words and morphologically related unexposed words compared with an active control condition. Norwegian second graders (N = 717) unselected for ability were individually randomized to either a morphological (n = 366) or a mathematical training program (n = 351). Both programs lasted for 8 weeks and were delivered as self-contained apps in a classroom setting. The morphological training built on the principle that frequency of target elements together with variation of nontarget elements can support implicit learning. Treatment-blind examiners assessed participants' meaning-based knowledge (word comprehension and definitions) and code-based knowledge (word reading fluency and spelling) at pretraining, immediately post training, and at follow-up 6 months later. An intention-to-treat analysis showed lasting effects of the morphological training on meaning-based knowledge of exposed words (posttest: d = .37; follow-up: d = .31) and unexposed words containing trained morphemes (posttest: d = .27; follow-up: d = .27) and code-based knowledge of exposed words (posttest: d = .22; follow-up: d = .13). For code-based knowledge of unexposed words, there were significant training effects at the posttest (d = .12) but not follow-up (d = .05). There were no significant effects on a far-transfer measure of general vocabulary. These results demonstrate that a brief morphological training program can produce lasting and educationally meaningful gains in students' word knowledge. Educational Impact and Implications Statement Words can consist of several meaningful parts, or morphemes, such as -ist in guitarist and re- in reuse. Understanding common morphemes helps children infer the meanings of new words. In this study, we tested the effects of working with an educational application (app) focusing on morphemes. Children completed app exercises such as sorting words or pictures according to their meaning, combining morphemes to build words, or identifying the correct word or morpheme to fit a sentence or picture context. We found that the app was effective in improving Norwegian second graders' ability to explain, understand, read, and spell words, including words which were not shown in the app, but which contained trained morphemes. The brief low-cost training produced long-term effects with a minimal burden on teachers.