I agree with Diane. I think the majority of the time spooking comes
from: boredom (trying to entertain themselves), feeling good/silly from too much
"hot" feed or not enough exercise or both, being defiant (trying to get you
off).
My 11 year old QH/Trak. cross will still "spook" at
things I know he is not afraid of; fly spray, the saddle pad, the poop
fork...but he only does it when I haven't ridden him regularly. If I let
him go more than 2 weeks I know he will be "spooky". I also think he is
being naughty, so when he "spooks" I make him work ( lots of backing up,
figure 8's, transitions, anything he thinks is work). If he
truly is afraid of something new, the working will get his mind off the scary
thing and back on me, I become bigger than the scary thing. And if
he's just being silly and naughty, the working will be the consequences of
his silliness. Very soon the "spooking" will stop because he
will know that hard work will follow and it's just not worth the "fun"
of spooking. Now, with this horse anyway, if I feel a "spook" coming on, I
give him a stern "Don't even try it!" in my "big, dominant" voice and a swift
kick if needed with it, and he stops his spooky behavior.