Hi Kristin,

In BLOCK(6.5,1) vs. BLOCK(3.5,1), the ,1 means that
each curve's peak gets scaled to 1. Now imagine 2
identical stimuli, except that one lasts 3.5 s, while
the other lasts 6.5 s, and picture the result at one
location in the brain.

One would except identical responses, except that
the 6.5 s BOLD response would be bigger (it would
convolve to a wider and higher signal). But if one
wanted to answer the question of which stimulus the
brain responded more to, the answer should be neither,
the responses were the same. The comparison is not
fair if one stimulus lasted much longer.

But using BLOCK(6) vs BLOCK(3.5) _does_ result in a
valid comparison, because the betas are essentially
scaled down by the convolution height. It is more
like the betas reflect the signal change as if the
events were instantaneous.

- rick