I hope you don't mind CC'ing the SPM mailing list so others can benefit.
I assume this is DCM for fMRI? You should indeed have one DCM containing all your conditions, unless there's good reason not to. So yes, I would recommend creating a single model. Feel free to post the details of your task / DCM design if you'd like them scrutinised.
From: Toshi Kawagoe [mailto:[log in to unmask]]
Sent: 16 February 2017 04:34
To: Zeidman, Peter <[log in to unmask]>
Subject: Re: different DCM results between simple averaging and BPA averaging
Thank you for your kind reply.
Your explanation was easy to understand.
At first, I did option 2 but I did not found the "Contrast of connections" button.
I create one DCM file containing one condition. So there are 2 DCM file per a subject because I had 2 conditions.
Maybe this way of creating DCM*.mat was not good, was it?
Then, should I redo making the DCM .mat file?
My best, Toshi