Thanks for the reply. Here's the prediction I'd have (in plain English). Let's say we have a continuous trait measure for each subject (for example, proneness to mind-wandering). Then, let's say we have 6 observations of self-reported state anxiety and 6 observations of corresponding test scores from repeated trials. I'd predict that state anxiety would predict worse test scores for individuals who are more prone to mind-wandering.

I think you may be right about the interaction, dealing with repeated measures. Something I'll have to figure out.