I'm not enough of an aviation know it all/historian so the only example I can
site off the top of my head is the Quickie, Q-2/200, Dragonfly, Flying Flea
family.

While the "little wing in the rear" isn't so little the physics are the same.
As long as the moment of the 2 "wings" move aft with an increasing angle of
attack, and forward with decreasing pitch the plane will be pitch stable at one
particular speed. This can be done simply by having the tail provide a down
force, but by properly selecting the airfoils so that the lift of the rear wing
increases faster than the front with increasing angle of attack you get the
same result.

I'm not a professional aerodynamisist, maybe even a poor amateur, and not a
very good teacher - so if your just learning about all of this in your PPL
ground school it might be a bit simpler to forget all about anything but
"conventional" airplanes for a while...........or find someone that can explain
it better than me.......which shouldn't be hard.

If you really want some interesting pitch stability mental exercise think about
a flying wing with negative sweep..........


Well well I am learning again.
My PPL ground school certainly disagrees with you!
Do you have any example of such a design?

TIA,
Karel