I read that the default setting of lme4 is listwise deletion. My data is in long format (repeated measures with two time points) and it doesn’t appear that it really deletes listwise (as I understand it, this would mean that subjects with missing values on the dependent variable at either T0 or T3 are not taken into account in the analysis). I get this impression when I look at the ‘number of observations’ on the output. This number corresponds exactly to the number of my data points, but only if I take into account the observations of the subjects who only have data for either T0 or T3. Any help?