[R-sig-ME] lmer(): Higher weight in case of more measurements

[Susanne Susanne]

Dear Mr Bates and Mr Bolker, Dear R-list,
 
I have a question regarding the lme4 package and would be very thankful if you could help me.
My data consists of several clusters with repeated measurements x.
Therefore, I want to use the lmer() function to regress the data using a mixed model:
 
lmer(y ~ x + (x | cluster).
 
I want to weight clusters, which have more measurements than others, slightly higher, as they provide more information.
 
Is this done automatically in the lmer() function or should I do it manually by myself? And how could this be realized?
 
I tried out small examples with fictitious data (and quite a few with real data) but it seems impossible for me to decide whether lmer() is weighting these clusters higher.
If I weight some clusters higher with the “weights=” argument, it seems to matter how many measurements the cluster has. If I set default weights it doesn't seem to matter.
 
Many thanks in advance,
 
Yours sincerely,

Susanne