The effects of word form variation and frequency on second language incidental vocabulary acquisition through reading

The purpose of this study was to investigate whether frequency of occurrence and the level of morphological form variation (i.e., none, inflectional, and derivational) exhibited by target words might interact to affect incidental acquisition through reading. An intact class of English as a foreign language learners (n=32) was given a copy of an unmodified 37,611-token English novel containing 49 target nonce words to read within two weeks. After reading, they were given two unexpected forms of assessment (meaning recall translation and meaning recognition multiple-choice). Meaning recall results indicate an average of 10 words having been acquired and meaning recognition results indicate an average of 25 words having been acquired. For the meaning recall data, a significant interaction effect between word form variation and frequency was found. Results point towards the conclusion that an increase in frequency may have a beneficial effect on acquisition for words whose tokens vary inflectionally, a marginal effect forwords that do not vary in form, and little to no effect on words that vary derivationally. Examination of the meaning recognition acquisition results for a subset of 29 target words occurring 2-4 times to control for frequency of exposure found a significant effect for word form variation. Post hoc comparisons indicated that participants acquired significantly more target words that did not vary in form. There was no significant difference in acquisition between those that varied inflectionally and derivationally. Taken as a whole, the results of the current study indicate that word form variation does affect incidental acquisition and it can indeed present second language learners with difficulties, especially when less frequent input is received of words that vary in form. Implications for future incidental vocabulary acquisition research and classroom pedagogy incorporating reading and vocabulary instruction are discussed.