> If 3dLME is recommended, could you provide an example of the syntax for a dyadic analysis with covariates at both
> level 1 (between individual subjects) and level 2 (between dyads) and using a compound symmetry error structure?

Try 3dLMEr. First, create a data table with columns like this:

dyad behavior relationship InputFile

The four columns code the dyad labels, behavior measure, dyad relationship and the FMRI data. For any two subjects within a dyad, use the same dyad label for both subjects and mark their relationship as 1; for a subject without a dyad, code the relationship as 0. Then, specify the model as

-model 'behavior + (1 | dyad) + (0 + relationship | dyad)'

> could you clarify whether this warning might apply to my situation: "Between-subjects covariates are generally
> acceptable. However EXTREME caution should be taken when the groups differ significantly in the average
> value of the covariate." Would "groups" in this case refer to different dyads?

If your effect of interest is the association of behavior with brain response regardless of a subject belonging to a dyad, the warning does not seem to apply to your case. In other words, the dyad relationship only comes into play when you account for the correlation within each pair in the model.

Gang



Edited 1 time(s). Last edit at 04/22/2020 09:59AM by Gang.