Error message when estimating group level interactions lmer When estimating a group level interaction I get the following error:
 model <-lmer(rtln ~ + ifIncongruent + gender + ifIncongruent:gender + (1|subj:ifIncongruent), data=dataset)
Error in validObject(.Object) : 
  invalid class "mer" object: Slot Zt must by dims['q']  by dims['n']*dims['s']
In addition: Warning messages:
1: In subj:ifIncongruent :
  numerical expression has 1789 elements: only the first used
2: In subj:ifIncongruent :
  numerical expression has 1789 elements: only the first used

I'm sure there is some obvious reason, I need to specify something. Does anyone know?
thanks,
 A: You're specifying ifIncongruent as both an effect and the grouping for the multi-level model.  When you put ifIncongruent after the "|" that was telling it that your data is nested within it's interaction with subj.  I doubt that's what you want.  Even if it is, you can't also have it as an effect as well.  Maybe you meant?
model <- lmer( rtln ~ ifIncongruent + gender + ifIncongruent:gender + (1 + ifIncongruent|subj), data=dataset )

EDIT:
Looking at your Stata output you may have meant
model <- lmer( rtln ~ ifIncongruent + gender + ifIncongruent:gender + (1|subj) + (0 + ifIncongruent|subj), data=dataset )

or shorter
model <- lmer( rtln ~ gender * ifIncongruent + (1|subj) + (0 + ifIncongruent|subj), data=dataset )

You DO NOT have separate intercepts for your random effects in the output shown here for your Stata model.  You'd need to print the random effects for that (in R that ranef(model)).  You do have seperate estimates of the standard deviation of random subject and ifIncongruent effects.  
You should really try to specify in regular language... not lmer... what you're trying to accomplish if this isn't it.  Describe the complete model you're trying to test.  At least describe the structure of your data or something.  All of these arbitrary variables you keep posting in your questions don't mean anything.  Craft a proper question and you can get a proper answer.
