Infants apparently do not get motion sickness, not that they can express their relief at their resistance — nor lord it over the rest of us.

But it has been suggested that the old also have some degree of immunity to the condition.

I am still waiting for that geriatric benefit. So far, my sense is that the older I get, the less resistance I have to the condition.

What is particularly interesting is that scientists still are not sure what causes motion sickness.

They know the conditions likely to produce it, but why a heaving ship or buffeted airplane or swaying car should produce those reactions … that’s what they don’t get.

What seems to be suggested most often is that motion sickness is a result of the brain receiving conflicting signals — feeling movement without seeing it. And the eyes and ears send the brain different information, which leads to confusion and then nausea.

Another suggestion is that the nausea that accompanies motion sickness stems from the brain believing the host may have consumed something toxic.

The brain, then, doesn’t know “poisoning” from “motion sickness” and deals with both by ordering up some vomiting.

If anything, I am more susceptible to motion sickness right now than I have ever been.

I have pretty much sworn off theme-park rides — or wish I had. I was a fairly keen roller-coaster rider until age 50 or so when an early-morning ride on Disneyland’s Space Mountain left me feeling queasy for the rest of the day.

So, no more roller-coasters.

Now, more rides are out, including the “shaking and spinning” sort many people find to be fun.

In a recent episode, I was impressed, in a very unpleasant way, at how quickly I showed symptoms of motion sickness.

First came the realization that this was going to be a shaking and spinning ride, and that my looking at the images would make the condition worse.

Still, my pulse skyrocketed. Within 25 seconds I felt sweat break out all over my face, perhaps a first for me, and certainly the fastest it has ever come over me.

The dread and horror of motion sickness was upon me. Many of those stuck at sea while it goes on practically lose their will to live.

So, on the ride, I immediately wondered “how long can this last?” and “can I told on till the end?”

The ride was perhaps two minutes in length, but it seemed far, far longer as I fought a desperate battle with my inner ear and/or brain.

I coped with it by closing my eyes or staring at my hands, which were motionless. (I also clenched up; which does no good at all but seems part of the typical reaction.)

I made it to the end, and didn’t feel dizzy when I climbed out of the “car”, but it was a new low for me — because it wasn’t that long ago I could stand these sorts of rides.

I have been seasick pretty much forever, which brought a degree of cruelty to my father’s jolly attempts to have the family sail from Long Beach to Catalina. I was semi-sick throughout. One of my brothers was often profoundly sick. My father, perhaps, was among the 30 percent of people who do not get motion sickness easily — though apparently nearly all humans will get motion sickness in extreme conditions.

I was hoping my advancing decrepitude would provide the relief some writings on the subject suggest is waiting for the aged. Not yet.

Meantime, I remain jealous of infants.