Galactic Odyssey by Keith Laumer is an enjoyable sf adventure story that includes a number of memorable ideas. My favorite appears in Chapter Nine when the protagonist, captured by alien slavers, gets put to work sorting apparently-identical glowing spheres into categories. He's strapped into an electricified training harness next to the conveyor belt, and then:
... A bulb came toward me and a sensation like a hot needle stabbed the middle finger on my right hand. I punched the key under it and the pain stopped, but there was another bulb coming, and the needle stabbed my little finger this time, and I jabbed with it, and there was another bulb coming. . . .
"It's a surefire teaching system," Fsha-fsha said in his cheery, sub-cellar voice. "Your hands learn to sort without even bringing the forebrain into it. You can't beat pain-association for fast results."
For the rest of the shift, I watched glorm-bulbs sail at me, trying to second-guess the pain circuits that were activated by Fsha-fsha's selections. All I had to do was recognize a left-forefinger or right ring-finger bulb before he did, and punch the key first. By the end of the first hour my hands ached like unlanced boils. By the second hour, my arms were numb to the elbow. At the end of three hours I was throbbing all over.
"You did fine," Fsha-fsha told me when the gong rang that meant the shift was ended. "Old Hruba knew what he was doing when he assigned you here. You're a quick study. You were coding ten percent above random the last few minutes."
That's typical Laumerian understatement, tongue-in-cheek humor with a twist of philosophy. After a rest Our Hero returns to the sorting line:
The training sessions got worse for the next three shifts; then I started to catch on --- or my eye and fingers did; I still couldn't consciously tell one glorm-bulb from another. By the time I'd been at it for six weeks, I was as good as Fsha-fsha. I was promoted to a bulb-line of my own, and the harness went back in the locker.
The Sorting training, as it turned out, didn't only apply to glorm-bulbs. One day the line appeared with what looked like tangles of colored spaghetti riding on it.
"Watch," Fsha-fsha said, and I followed through as he sorted them into six categories. Then I tried it, without much luck.
"You have to key-in your response patterns," he said. "Tie this one . . ." he flipped his sorting key, " . . . to one of your learned circuits. And this one . . ." he coded another gob of wires, " . . . to another. . . ."
I didn't really understand all that, but I tried making analogies to my subliminal distinctions among apparently identical glorm-bulbs --- and it worked. After that, I sorted all kinds of things, and found that after a single run-through, I could pick them out unerringly.
"You've trained a new section of your brain," Fsha-fsha said. "And it isn't just a Sorting line where this works; you can use it on any kind of categorical analysis."
And of course, this new mental power comes in quite handy at a critical juncture many pages later --- just as, in Real Life, it's valuable to learn how to walk, talk, and do a variety of other activities at a non-conscious level ...