Hi Donald and Cyril,
Thanks for the feedback. Let me explain a little more what I currently have: I have a single-subjects model for each subject, where I input 10 conditions, and set up a contrast to compare condition 1 with condition 10 (ie 1 0 0 0 0 0 0 0 0 -1 with T-test)
Then I forward all subjects .con.nii's into a second-level, where I want to test the effect of a behavioural score, and how it changes between Trial1 and Trial10 (presumably using an F-test such as 1 0 0 0 0 0 0 0 0 -1). Based on some discussions on the SPM list, I thought I would look at it by entering a behavioural covariate (ie Trial10Performance - Trial1Performance). Hence, I thought I would have 1 value per subject.
Do you have any suggestions of how to include this covariate? I guess it's more of a time-varying covariate? Or a repeated measures with one behavioural value?