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Dear SPMers, I have a found the effect of my factor A (which has three levels; one for each group of subjects). Additionally, I found the effect of a covariate (a neuropsychological score). All effects are second-level. How can I now figure out, if the correlation with the covariate is different for the levels of factor A (three groups of subjects; different corralations with the covariate in each group of subjects). I was thinking of calculating the interaction between factor A and my covariate, but I can neither figure out how to do this in SPM5 nor if this is the correct approach. Thanks alot for your help! Best wishes, Tim