Consider a bird.
A real Keatsian fowl.
Something that can warble
from dusk to dawn,
a constant warbler.
Now what I’m going to do
is take the bird
and touch the tip of my pinky
to its anus,
apply a little pressure.
What we want to observe
is the effect of this pressure
on the warble:
does the pitch drop?
does it do so continuously?
or does it stay constant till a break point?
Warbling and the pressure could be
completly independent.
Maybe the pressure has no effect?
But, we want answers to these questions.
That is why we perform these tests.