Re: No Pain, No Gain
I agree that feeling the pain is important in uke's learning how to go to the painless place, ideally resulting in uke's submission via pin or throw. Uke's natural reaction also tells nage how to induce pain, and what the thresholds are among mild, moderate, and severe pain. Now, every uke has his or her own thresholds, but the variations here usually are not major. I like your allusion to classical conditioning (CS, CR, UCS, UCR), but I think operant conditioning (Skinner) may be relevant as well. A rat (so often used because their brains are so similar to that of humans) placed on one side of a cage, learns to press a lever on the other side to get a food reward. When an electrified grid is placed between the rat and the lever, not even a starving rat will cross the grid for its food reward. Setting up the cage differently by inserting an electrode into the rat's brain pleasure center (hypothalamus), and setting the lever to shock and stimulate pleasure, behavior is different. Not only will a rat cross the painfully electrified grid to get to the lever, but it will press it hundreds or thousands of times a minute.
The pain I've felt in paired practice has been mild-moderate, and it's usually quite temporary as long as I don't fight against nage's guidance. The pain we endure in the dojo reminds me of the rat's electrified grid. Most Aikidoka find frequent but abrupt discomfort to be well worth the pleasure of not only endorphins, but just as importantly the sense of accomplishment derived from doing our best and advancing one class at a time, one lever press at a time.