You should be using the flexible factorial module and including a subject factor in the design matrix.

Best Regards, 
Donald McLaren, PhD

On Wed, Sep 9, 2015 at 4:45 AM, 栩Xu龚Gong <[log in to unmask]> wrote:
Dear SPM experts,

My experiment is a 2*3 within-subject design. In the 2nd-level analysis, I use the 2*3 full factorial model. I found the brain activation in the interaction(F-contrast). However, I am not sure how to explain this 2*3 interaction?  Would you please give me more information about this? Thanks!

Best regards,