No abstract

Type/Token Ratios have been extensively used in child language research as an index of lexical diversity. This paper shows that the measure has frequently failed to discriminate between children at widely different stages of language development, and that the ratio may in fact fall as children get older. It is suggested here that such effects are caused by a negative, though non-linear, relationship between sample size (i.e. number of tokens) and Type/Token Ratio. Effects of open and closed class items are considered and an alternative Verbal Diversity measure is examined. Standardization of the number of tokens before computing Type/Token Ratios is recommended.

Lexical diversity is an important indicator of language learners’ active vocabulary and how it is deployed. Traditionally it has been measured by the Type-Token Ratio (TTR), the ratio of different words to total words used. Unfortunately, TTR is a function of sample size: larger samples of words will give a lower TTR and even commonly used measures derived from TTR which are claimed to be independent of sample size are problematic. To overcome this, the authors have developed an innovative measure of vocabulary diversity, D, based on mathematically modelling how new words are introduced into larger and larger language samples, and have produced software (vocd) to calculate it. Previous research by the authors into language proficiency interviews (Richards and Malvern, 2000) investigated linguistic and discourse accommodation of teacher-testers using a wide range of student and teacher variables. In a study of teenage learners of French, the aspect of teachers’ language in oral interviews that was most responsive to the ability of their students was lexical diversity. The analysis reported here focuses on this finding in greater depth using the new measure, D. The relationship between D and other measures of foreign language proficiency is investigated, the Ds of students and teachers are compared and the correlations between teachers’ D and students’ proficiency are computed. Results firstly demonstrate the validity of D as a measure of vocabulary diversity and the effectiveness of vocd as a tool to analyse language data. Secondly, with regard to accommodation processes in oral testing, the two teachers did not finely tune their vocabulary diversity to the proficiency of individual students. Instead, each teacher roughly adjusted his or her language to the ability of the class they examined.

A current debate in the literature is whether all declarative memories and associated memory processes rely on the same neural substrate. Here, we show that H.C., a developmental amnesic person with selective bilateral hippocampal volume loss, has a mild deficit in personal episodic memory, and a more pronounced deficit in public event memory; semantic memory for personal and general knowledge was unimpaired. This was accompanied by a subtle difference in impairment between recollection and familiarity on lab-based tests of recognition memory. Strikingly, H.C.'s recognition did not benefit from a levels-of-processing manipulation. Thus, not all types of declarative memory and related processes can exist independently of the hippocampus even if it is damaged early in life.

No abstract