John Gierach is a writer I usually enjoy, but when I was sent a review copy of his new book the other day, one small line touched a real sore point.

“If you wanted a fish that could sip white wine and discuss Italian poetry, you’d look for a trout,” Gierach wrote. “If you needed a ditch dug, you’d hire a carp.”

That kind of statement defies common sense and biology. If you could have a conversation with a trout, it would more likely swill Budweiser and discuss “Who Wants to Marry a Millionaire?”

Trout can be so hard to catch because they are dumb, at least by the standard of ability to learn. These are creatures that can be dying of malnutrition and yet fail to recognize food in front of their noses. Every veteran fly angler has had the experience of watching trout ignore a new fly for the first hours or even days of a hatch before the fish figure out it’s something to eat.

Tests show that carp, when measured by the learning-ability standard used to measure human intelligence, are probably the smartest fish in fresh water. An English company that makes fish-attracting scents kept carp in a big tank and tested new flavors by putting them on bits of bread and dropping them in the water to see how the fish liked them.

The researchers ran out of bread one day, so they grabbed some cotton balls, put the flavoring on them and dropped them into the tank. They learned they could fool a carp into eating a cotton ball — but only once. After the initial experience, the carp ignored cotton balls, no matter what flavor was on them.

Trout, on the other hand, seem to ignore food offerings not because they are wary but because they don’t recognize food unless it looks and acts exactly like something they have seen before.

Trout will ignore an artificial fly if it doesn’t move exactly like a real fly would. I’ve also found that even if you stick them with a hook and miss them, most trout will be willing to hit a fly again in 30 minutes or less if a good hatch is on.

But where they are heavily fished in Europe, carp are so well-educated and have such long memories from their bad experiences that anglers use sinkers that are irregularly shaped and painted to look like stones.

In fact, carp fishing didn’t really take off in England until about 15 years ago, when some bright spark came up with the idea of putting baits not directly on the hook but on a hair rig, a short length of line attached to the hook near the eye. That’s because carp had learned to feel a bait with the barbels under their mouths and reject it if they felt metal.

I’m making this distinction between carp and trout not because I think one is inherently superior to the other. Sure, trout are dumb, but that doesn’t make it any less fun to catch them.

Sometimes it makes it more challenging, and I usually find that to be a good thing.