Effects of morphological instruction on vocabulary acquisition

The effects of a 20-session intervention targeting morphological word structure on vocabulary knowledge were investigated in four Grade 4 and 5 classes, assigned randomly to treatment and control conditions. Hierarchical regression analyses controlling for initial vocabulary showed significant instructional effects on morphological analysis and vocabulary with words that were taught directly and novel words built on bases that were taught in the context of other derivations, but not for words with untaught bases. Results indicated that the treatment group made better use of pre-test vocabulary knowledge in learning new vocabulary. Results are discussed in light of the growing debate regarding whether to teach many words in a shallow way or to provide deep, rich instruction about fewer words.