This is a report of a research project to investigate vocabulary use by candidates in the current (since 2001) version of the IELTS Speaking Test, in which Lexical resource is one of the four criteria applied by examiners to rate candidate performance. For this purpose, a small corpus of texts was created from transcriptions of 88 IELTS Speaking Tests recorded under operational conditions at 21 test centres around the world. The candidates represented a range of proficiency levels from Band 8 down to Band 4 on the nine-band IELTS reporting scale. The data analysis involved two phases: the calculation of various lexical statistics based on the candidates’ speech, followed by a more qualitative analysis of the full transcripts to explore, in particular, the use of formulaic language. In the first phase, there were measures of lexical output, lexical variation and lexical sophistication, as well as an analysis of the vocabulary associated with particular topics in Parts 2 and 3 of the test.
The results showed that, while the mean values of the statistics showed a pattern of decline from Band 8 to Band 4, there was considerable variance within bands, meaning that the lexical statistics did not offer a reliable basis for distinguishing oral proficiency levels. The second phase of the analysis focused on candidates at Bands 8, 6 and 4. It showed that the sophistication in vocabulary use of high-proficiency candidates was characterised by the fluent use of various formulaic expressions, often composed of high-frequency words, perhaps more so than any noticeable amount of low-frequency words in their speech. Conversely, there was little obvious use of formulaic language among Band 4 candidates. The report concludes with a discussion of the implications of the findings, along with suggestions for further research.