The effects of phonics instruction on L2 phonological decoding and vocabulary learning

Phonological decoding, defined as the ability of using the systematic knowledge of a language’s grapheme-phoneme correspondences in order to generate pronunciation based on orthographic context, has been found to be facilitative of the acquisition of reading comprehension in both first language (L1) and second language (L2). Moreover, research into L1 learning has consistently demonstrated a strong relationship between decoding proficiency and vocabulary acquisition. Recently, the relationship between L2 decoding and word learning has begun to be explored. There is a strong theoretical support for a causal relationship between the variables: fast and accurate decoding of written forms provides reliable phonological representations which support the operation of phonological working memory; psycholinguistic evidence suggests that this, in turn, plays a central role in learning novel phonological forms. Further, knowledge of a language’s grapheme-phoneme correspondences allows the orthographic and phonological representations of new words to be mutually reinforcing. Previous studies have indeed found positive correlations between both the speed and accuracy of decoding on the one hand and success in intentional word learning on the other amongst learners with alphabetic but not morphemic L1 backgrounds. This is consistent with the view that morphemic learners are more likely to process words visually as whole units. However, there has been no experimental evidence thus far, which could prove the causal link between decoding and vocabulary learning. Against this backdrop, an intervention study was conducted in which a twelve-week programme of systematic phonics instruction, covering 101 English grapheme-phoneme correspondences, was implemented to three classes of first-year English majors in three universities in Wuhan, China. The comparison participants received a twelve-week English phonology instruction programme focusing on the pronunciation of 44 English phonemes and other pronunciation tips, but not explicit instruction on English grapheme-phoneme correspondences. To evaluate the effectiveness of the phonics instruction programme, two tests were administered both before and after the intervention: (a) an English decoding test; and (b) a vocabulary memorisation task, followed by immediate recall and recognition tests of the phonological and written forms of the new words. Participants’ scores at the two time points and between the two groups were compared. Participants who followed the phonics instruction programme demonstrated a clear and significant advantage over their counterparts in the comparison group in terms of the number of both (a) whole words and (b) individual graphemes that they pronounced correctly in the English decoding post-test. Moreover, comparison of participants’ realisations of English graphemes before and after the instruction programme suggests the influence of cross-linguistic transfer. For instance, the English graphemes that also exist in Pinyin and share the same pronunciations witnessed the highest accuracy at t1, while those that exist in Pinyin but have different pronunciations in the two languages appeared to be those associated with least improvement at t2. In the vocabulary memorisation task, the intervention participants achieved significantly higher scores at t2 in the oral recall, written recall and aural recognition test compared to the comparison groups. However, no significant differences between the two groups were observed in the written recognition test. The results suggest that explicit phonics instruction can be effective in improving the English decoding proficiency of Chinese university EFL learners. Further, the findings are consistent with the hypothesis of a causal link between L2 decoding and vocabulary learning. The study may also inform the design of future phonics instruction programmes for this population of learners: for example, certain English graphemes appeared to need more explicit instruction than others.