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Hi Esther,

In the 1st level, the contrasts you already have are:

S11 vs S21: 1 0 -1 0
S12 vs S22: 0 1 0 -1

Now you'd just add, for each subject:

(S11 vs S21) vs (S12 vs S22): 1 -1 -1 1

It should do what you need. These can be passed up to the higher level and used to make group inferences.

All the best,

Anderson



On 27 August 2015 at 14:23, Esther Heckendorf <[log in to unmask]> wrote:
Hi,

I have a question about the set up of a three level analysis in FSL. I have two stimuli with each two levels (S11, S12, S21, S22) and I have created the contrasts S11 vs. S21 and S12 vs. S22 in the lower-level analyses. Now, I would like to calculate the following contrast: (S11 vs. S21) vs. (S12 vs. S22). Is it possible to calculate this contrast in a higher-level analysis using the COPEs of the contrasts S11 vs. S21 (contrast 1) and S12 vs. S22 (contrast 2) as inputs? For an example with 3 participants I would set up the following model:

                   EV1 EV2 EV3
Input 1         1      0     0
Input 2         0      1     0
Input 3         0      0     1
Input 4        -1      0     0
Input 5         0     -1     0
Input 6         0      0    -1

Input 1 = First contrast for subject 1
Input 2 = First contrast for subject 2
Input 3 = First contrast for subject 3
Input 4 = Second contrast for subject 1
Input 5 = Second contrast for subject 2
Input 6 = Second contrast for subject 3

Contrasts and F-tests:
                 EV1 EV2 EV3
subject 1     1     0     0
subject 2     0     1     0
subject 3     0     0     1

Is it possible to calculate the contrast (S11 vs. S21) vs. (S12 vs. S22) in this way or is it necessary to set up the model for each subject separately?

Thanks,
Esther