Dear Experts,

I’d like to explore an interaction analysis which I created using SPM8 for EEG. Specifically, I’d like to represent what I can see by eyeballing the contrast estimates (plotting the effects of interest) from a significant peak, with data that can be statistically tested. To do this I was wondering how the data in the variable named ‘contrast.contrast’ is generated when I plot the effects of interest contrast for a peak of activation, and whether the underlying data that generates variable this is accessible to me?

I realise I could explore the interaction further by masking the interaction by another (simpler) contrast, but interpretation in this manner gets messy because of the data being distributed in both space and time (i.e masking might highlight the contribution of a simple effect to the interaction but at a different place / time, and cannot determine that this *drives* the interaction, only that it is present).

Any help to locate the data that create contrast.contrast would be greatly appreciated, plus I’d love to hear any other (non-masking) solutions to this problem.

Many thanks,

Gemma.

Miss Gemma E. Barnacle

PhD Candidate

103E Zochonis Building

School of Psychological Sciences

The University of Manchester

M13 9PL.

tel: (0161) 275 0953

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