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Hi Helmut,

Thanks for your help! Much appreciated. You actually brought up some very interesting questions that I've been considering in theory based on past research, but haven't pinned down as a model. Just to clear up a few things, please see my comments inline:

Well, there are different options. E.g. set up one contrast [1 -1 ...] on single-subject level to test for "first five" > "second five" and a second contrast [0.5 0.5 ...] corresponding to "average" = (first five + second five)/2.
I'm wondering what it would mean to look at 'average'? Is the hypothesis here that first five = last five? (ie that activation doesnt actually change from early to late trials). 
 

To test for differences between first and second five trials on second level set up a two sample t-test based on the first con images (first bunch of files selected = group 1, second selection = group 2).
Do you mean group 1 would be my young subjects and group 2 my old, right?
Within this second level model, [0.5 0.5] corresponds to "first five" > "second five" across groups, [-0.5 -0.5] corresponds to "first five" < "second five" across groups,
Got it!
[1 -1] corresponds to "(group 1 first five - group 1 second five) > (group 2 first five - group 2 second five)", [-1 1] corresponds to "(group 1 first five - group 1 second five) < (group 2 first five - group 2 second five)"
That's actually an interesting hypothesis! Basically we'd be asking whether the difference in activation between early and late stages of learning change as a factor of age.. right? That's really great!

To test for group differences across conditions set up a two-sample t-test based on the second con images, the corresponding contrast vector within the second-level model is [1 -1] for group 1 > group 2 and [-1 1] for group 2 > group 1.
I guess this model would be asking how much difference there is between groups across the whole task period, and doesn't really account for any changes from early to late. In fact, would this be too different from just having, on the first level, 1 condition with 10 onsets (ie not dividing into early and late conditions), and forwarding this into a simple two sample t-test with ie [1 -1] for group 1 > group 2?

Many thanks for your help!!!
Joelle