Neither of our female companions would agree to sleep with Eric. So I said I would.

He laid down on his side of the bed, I laid down on mine and turned off the lights. After a few moments, my breathing slowed and I started to drift, floating in that weightless place between not yet sleep and no longer fully awake. I was thinking happy thoughts.

And then Eric kicked me in my kidneys.

It was a hard shot, heel first, and my eyes flew open. I muttered something impolite. Not that Eric heard me. My 7-year-old grandson was sound asleep. In the darkness I could hear my wife and daughter slumbering peacefully in their bed on the other side of the hotel room.

I listened for the sound of snickering, waited for one of them to say, “I told you the boy sleeps like something out of a kung fu movie.” Hearing nothing of the sort, I lowered my head gingerly back to the pillow and closed my eyes. Soon I was drifting toward dream world again. I remember that I was accepting my Nobel Prize with a humble and eloquent speech.

Then Eric kicked me in the ribs.

He left the foot there this time, wedged fast against my vertebrae. I reached around and grabbed his shin, shoving it harder than strictly necessary back to his side of the bed.

Obviously, the boy was channeling the spirit of Bruce Lee. But I’d be ready for him next time. I grabbed a spare pillow and planted it firmly between his feet and my torso, then closed my eyes and lay back with a sigh. Soon I was floating pleasantly again, trying to figure out how much of my new lottery winnings it would take to purchase a modest island in the Caribbean.

And Eric punched me in the head.

So you can appreciate my interest in a new British study on the way we sleep and what that says about our personalities. The study was authored by Chris Idzikowski, director of the Sleep Assessment and Advisory Service and a visiting professor at the University of Surrey. He surveyed 1,000 sleepers and reports that he found a high correlation between favorite sleep position and personality type.

For instance, people who sleep on their backs with their arms at their sides (the “soldier” position, the professor calls it) are said to be quiet and reserved, demanding of themselves and others. “Starfish” — people who sleep on their backs with their limbs splayed — are attentive to others but don’t like to receive attention themselves. “Freefallers” sleep on their stomachs and might seem outgoing but are very touchy about criticism. “Yearners” lie on their sides with arms extended; they are rational and open-minded, but also given to cynicism and suspicion.

And so on.

Anyway, while the study is interesting and all, its obvious flaw is that it sheds no light on what I will call the “Jackie Chan” position — spasmodic kicks and sucker punches. It would be nice to know more about that, especially since I keep finding myself lying next to those kinds of sleepers on family vacations.

A few years ago at Disney World, my middle son beat me black and blue over the course of two nights. Finally, we paired him with Eric. May the best man win.

This year, though, I wound up next to Eric with nothing but a pillow for protection. And as it turns out, a pillow is pretty useless for blocking a roundhouse kick. Sometime after 1 in the morning, I finally realized that. Staggering out of bed, I got two armchairs and sat them facing each other, found a pillow and a blanket, then lifted Eric from the bed and laid him in that little cocoon.

I hobbled back to bed, determined to salvage what was left of the night. My eyes closed, my mind roamed and Halle Berry reached for me, pleading for me to take her in my arms. I wanted to, but I couldn’t.

My body was killing me.