Why do some people lack a sense of humor?

[AFTT47]

There's probably a technical term for this but for the lack of knowing what it is, I'll call it 'Stimulation Resistance'. Here's how it works:

Let's say there is a Stimulation Threshold for everything and we can assign it a number. If it's for something we like, the Stimulation Threshold starts really low. You meet someone you like of the opposite sex and the Stimulation Resistance for kissing them is very low - practically zero. If you do kiss them - wow, there are church bells. But the next time you kiss them, it takes a little more to get the same effect. Been there, done that, right? The wow factor decreases every time you do it. There is more Stimulation Resistance. It takes more and more to get the same effect. It may level off eventually. It's still nice but no big deal. Or it may even get to the point that you would get more excited about kissing Barbara Bush/Donald Trump. That's why people "cheat". It overcomes your Stimulation Resistance.

It's no different with humor. The first time you are exposed to a particular piece of humor, it may tickle your funny bone. The next time, not so much. If you hear it enough times, it may even become tedious.

As a person gets older, his/her Stimulation Resistance to any specific thing is going to get higher and higher. Eventually, nothing of familiar experience is going to have much of a positive effect. It may even have a negative effect.

By the time you get to be my age, it may take a lot to make you laugh. It used to be as simple as someone farting in an elevator. Now it would take the thought of Donald Trump having sex with Barbara Bush on a railroad track and right before they simultaneously come, they are run over by a freight train - and the event was being televised to a world-wide audience and commented on by a panel of Republicans and members of the Vatican who all thought the tracks were inactive.