Falling into the ravine. It's easy to say, "Look for a better strategy," but it's not so easy to do. You may have an idea that playing three balls would be better, but perhaps if you try for that setup, you'll fall into one of the machine's traps. To find a better pinball strategy, you have to test your idea in practice, but to do that, you have to deviate from the strategy you already know how to do so well. Figure 4.2 shows my average progress on the Black Knight, but Figure 4.3 shows the same progress without averaging out some of the details. In front of each plateau is a ravine. Whenever I tried to improve, I didn't experience a great leap forward until I had experienced a small stumble backward.

Withhold quick criticism of teammates' ideas, in order to keep the ideas flowing. Although testing is crucial, few ideas are so dangerous they can't be allowed to live for the few moments it takes to reconsider our initial reaction to them.