VOCD manual

[Brian MacWhinney]

Dear ChiBolts,

    Comparing across these various studies and their new analyses, Fergadiotis et al. support the conclusion from the earlier study by Owen and Leonard regarding the fact that VOCD is still sensitive to sample size, although less that TTR.  However, both MATTR and MLTD seem to avoid this problem to the extent that they do not correlate with TTR, but rather with each other.  Given that both MATTR and MLTD are relatively sample-size-independent measures, one may want to turn to other criteria to decide which to use.  The advantage of MATTR is that its computation and interpretation is so transparent.  The advantage of MTLD is that it has been used more widely in the recent literature (outside of child language).  We have implemented MATTR in CLAN.  Whether or not we should implement MTLD is unclear.

Best,

—Brian MacWhinney
> On Aug 20, 2015, at 9:31 AM, Amanda Owen Van Horne <ajowen at gmail.com> wrote:
> 
> Also see 
> 
> Owen, A. J., & Leonard, L. B. (2002). Lexical Diversity in the Spontaneous Speech of Children With Specific Language ImpairmentApplication of D.Journal of Speech, Language, and Hearing Research, 45(5), 927-937.  
> Bottom line is that VOCD is better than TTR, but less transparent.  It does still vary with sample size, but to a lesser degree. 
> 
> McCarthy, P. M., & Jarvis, S. (2010). MTLD, vocd-D, and HD-D: A validation study of sophisticated approaches to lexical diversity assessment. Behavior research methods, 42(2), 381-392.
> Compares various methods of computing D.  Recommends  a variety of measures. 
> 
> Koizumi, R. (2012). Relationships between text length and lexical diversity measures: can we use short texts of less than 100 tokens. Vocabulary Learning and Instruction, 1(1), 60-69.
> Recommends MLTD
> 
> 
> 
> On Wednesday, August 19, 2015 at 9:46:58 AM UTC-5, Amber wrote:
> In fact, perhaps I should just post my question on here. The CHAT manual talks about calculating D and states that it can be done on samples as small as 50 tokens. However, reliability is less good for small samples. Could anyone advise me on whether VOCD is still a more valid measure than TTR, even for small transcripts (e.g., during a shared-book reading session)? I assume that as long as the sample is large enough for KIDEVAL to be able to give me VOCD values then it is OK?
> Thanks
> Amber
> 
> On Wednesday, 19 August 2015 15:36:05 UTC+1, Amber wrote:
> Dear all
> 
> The CLAN manual contains the following link, which no longer appears to work. 
> 
> http://childes.psy.cmu.edu/manuals/vocd.doc <http://childes.psy.cmu.edu/manuals/vocd.doc>
> 
> Is there a new link to the VOCD manual/another similar article? 
> 
> Many thanks
> Amber
> 
> 
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