MLU counts

[Brian MacWhinney]

Dear Nina, Yonata, and Info-CHILDES,
  The discussion of how to handle MLU in morphologically rich languages has
been on the table since the 1960s without any real resolution.  Yonata's
guidelines seem to reflect current state of the art and seem just about
right.  However, it seems to me that people working with morphologically
rich languages should really compute two indices.  The first would not be
cross-linguistically meaningful, but would be maximally meaningful within
the language.  That index would count morphemes in terms of what they
express.  Here, you still may wish to be a bit conservative.  For example,
do you really want to count the German article "die" as four morphemes
(definite, case, number, gender)?  I would say not.  Maybe two morphemes
would be about right (definiteness and case-number-gender).
  The second MLU for morphologically rich languages should be constructed on
the basis of a real comparative program of research.  Comparing normal
children of similar ages in similar urban (or rural) environments and
similar (mutually culturally relevant) activities, can you come up with a
method of scoring that yields parallel counts across morphologically rich
language (Hebrew, Inuktitut, Hungarian) and an analytic one (English,
Chinese).  As far as I can tell no one has yet attempted this obviously
important but perfectly feasible study.

--Brian MacWhinney