Brush Shape Dynamics

Hi Everyone,

Am I misunderstanding an option in the Brush Shape Dynamics palette?
I'm trying to create a brush that rotates 360º continuously as I
paint. I could have sworn I've come across similar brushes before, but
when I try to set the brush up myself with a custom tip I can't get it
to rotate. It looks great in the brush options palette, but when I try
to paint the options don't seem to affect the brush.

Here is a screenshot (http://benjaminshepard.com/dump/psbrush1.gif) of
the
palette with an example of what is actually drawn below it. I get the
same results with a tablet or mouse. I can up the angle jitter (from
1-100%) and the
brush will rotate erratically, but I'm looking for a nice
uniform stroke that rotates like in the screenshot of the brush
palette.

Am I missing an option somewhere or is this impossible?

.