> I want to calculate the anger+fear activation map but I am confused how to average this
Do you get the average effect between anger and fear at the subject or population level? At the subject level, if you just want to get the effect estimate, do
3dcalc -a anger -b fear -expr “a+b” -prefix ...
If you want to get both the average effect and its statistical evidence, you would have to achieve that with -gltsym by running 3dDeconvolve with the option -xrestore
Gang