My 2 cents:
1. The ball and the pins know when you've delivered the ball in a relaxed manner. (Remember the last time the game was out of the wood and your last 3 strikes came so easily?)
2. When the ball, ball speed or line played is not quite right, the pins tell you: unless you're leaving dead stoned 8 pin (or 9 pins for lefties), any leaves have a reason. After the above (wrong ball, wrong ball speed, wrong line), there are these reasons:
- missed your target by too much
- too much or too little ball speed, as it varies from you had been throwing the past few frames
- too much hitting up on the ball or just too much "hand" or revs, as it varies from what you had been doing.
The right ball and the right line can make up for some degree of variance in target or ball speed or rev rate, but too much variance and the pins that remain standing tell you you're doing one or more of these things too differently than you had been or should be doing.
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"None are so blind as those who will not see."