Think in 2D about averaging two sine waves that are shifted 90 degrees from one another.
The length of of the resulting line will be far less than that of either curve.
On 05/11/2011 11:20 PM, Michael Waskom wrote:
Hi Bruce,
I've seen this brought up on the list a few times, and, I have to admit, I've never really been able to wrap my head around it. The naive part of my brain feel like, if fsaverage is an "average" subject, it should be smaller than about half of subjects but also larger than about half of them. I'm sure I'm just not thinking about it quite the right way, but would you mind unpacking this a little bit? I suspect I'm not the only one for whom this is somewhat unintuitive.
Thanks!
Michael
On Wed, May 11, 2011 at 6:05 PM, Bruce Fischl <fischl@nmr.mgh.harvard.edu mailto:fischl@nmr.mgh.harvard.edu> wrote:
2. The surface area of fsaverage is less than any individual, so you *definitely* don't want to use it.