Very difficult, unless you finesse the problem by tying your measurement to a known physical measure such as time.
An anthropologist set up a boom box in a jungle and invited some villagers to come and listen. When he played Mozart, they wept. When he played disposable music, they left.
All he had to do was measure the time it took for individuals to leave, and he would have solved the OP's problem.
I've heard this story quite a few times, but I've done some pretty extensive searches, I have yet to find the source for this.
Do you have more information on the source for this?
I just get the idea, that this story might be apocryphal.