I was riding to racquetball the other day, and the memory of a commercial popped into my head.

The spot — which played ad nauseum on my favorite radio station — was for a soft drink. In it, the pitchmen “secretly placed a microphone” in a curmudgeon’s noggin. As he sipped the magic elixir, though he still appeared grumpy on the outside, the microphone picked up his uncontrollable inner glee brought on by the miracle beverage.

Egad, I hated that ad.

But it popped in my head because I wondered just what my sick brain would broadcast as I pedaled about if I had a mic secretly planted in my gourd.

I assumed most of my saddle-bound thoughts likely would get me slugged — like, “Nice driving, $&%#,” or, “Thanks for cutting me off, “&^%#.” So I tried to be cognizant of my cognizance and actually pay attention to my thoughts.

It was no idle exercise.

I know some folks swear they do their best thinking while out for a run.

My thoughts when I run are along the lines of, “Oh, my … gosh … how much … farther? Ow … this … hurts.” I even pant in my head.

On the bike is another matter.

I find cycle commuting far less taxing than running, so I figured all that extra energy would lend itself to cranial flexing.

I thought I’d find I actually carry out some pretty decent conversations in my head while riding, which is something of a surprise. Anybody who ever has talked to me pretty quickly figures out I’m not the best conversationalist.

In my head, I weave some of the most beautiful, intricate verbal tapestries … then I open my mouth, and the words tumble out like Scrabble tiles and clatter about the floor.

Unfortunately, most of my between-the-ears linguistic jousts are the synaptic equivalent of talking about the weather. All I seem to want to chat myself up about is the wind or the sun or the heat or the cold.

Man, am I dull.

When I’m not dazzling myself with observations about the relative humidity, I’ve found my mind’s churning far faster than my legs.

Trouble is, those thoughts are even more shallow than ponderings about the weather.

The one time I carried on a serious train of thought, I was closing in on a solution to the whole world-peace thing, solving nuclear fusion and oh-so-near to a cure for cancer when … I looked up and saw an import, stopped at a red light, growing awfully large in my field of view. I slammed on the brakes, swerved, veered, just missed the bumper, glanced off the curb, and — poof! — all those deep thoughts just disappeared.

Ever since, my cycling gray matter has been more occupied with Fido-worthy musings than Nobel Prize-type stuff.

As in, “Ohhh, pretty. BUTTERFLY! Um, hungry. Pretty. BIRDIE! LEAF! Pretty. I have an itch.”

Now that I, um, think about it, that microphone might not be such a good idea after all.

Then again, one thing this thoughtless little thought experiment proved is, there’s nothing quite like thinking about thinking to make your thoughts turn turtle, hiding away in their little shells until they can plod forward again, unmolested.

I think, anyway.