ozspit,
What pimminz just said and..........

the science of aerodynamics offers some explanation with something they call pitching moment. They offer measurements of it in plots and formulas to predict what'll happen because of it. And in effect, what happens because of it depends on lots of things, most just mentioned.

The wings configuration at any moment gives you an airfoil that's a resolution of the position of all it's parts. If the flaps are up, the spoilers down, no inspection covers flapping, etc you've got an airfoil that probably is producing a pitching moment, and it's probably more or less stabilized by the entire airframe and specifically by the horizontal tail. When some of those movable parts are moved all that changes. And one of the forces in play is a new pitching moment. And if you can find a plot that matches the new configuration, you just might find a pitching moment quantified. With pencil and paper you can figure it all out. And get a better insight into the whys and whats. And you're going to have to take more than just the pitching moment into consideration.

Of if you know a pilot, and especially one with hours in the particular subject airplane, you can just ask what happens. You'll certainly find out the "what".

And a number of people have mentioned that different things happen with different airplanes. And different things happen with the same airplane when different amounts of different things like settings or speeds are part of the picture. There isn't going to be one simple answer to cover even one simple configuration of flaps. or spoilers. or airspeeds. etc