Hi Roger and Emilia, and others,

I just wanted to say that in Emilia's data, she has 36 subjects and 20
items. Roger, would you agree that it is very difficult with this amount of
data to accurately estimate the full variance-covariance matrices for
subjects and for items random effects, especially the correlation
parameters? The numbers that lmer returns, for such sizes of data, are
pretty wild estimates, and often have no bearing to the true underlying
correlations. I think that in this situation we might be asking too much
from lmer, without giving it enough data. If, on the other hand, we have a
lot of data by subjects and items, it becomes possible to estimate these
parameters.

I believe this may have been, at least partly, the intent of Douglas Bates'
original message about overparameterization.

--
Shravan Vasishth
Professor for Psycholinguistics and Neurolinguistics
Department of Linguistics
University of Potsdam, Germany
http://www.ling.uni-potsdam.de/~vasishth

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