Keeping my mouth shut when I'm trying to test something might be my biggest problem here. Trying not to help someone figure something out is just plain painful! Watching in horror through my first batch of usability testing, I realized something: every glitch that had never shown up before decided that it was the perfect time to make their presence known. The shortcuts didn't work, the timing was off and somehow things were moved around. I didn't even hand my computer to a second tester. There was no way I could.
The article definitely caught me at something I'm bad at doing: keeping my mouth shut. "By simply mentioning something in a question, you draw attention to it." Forcing myself not to say anything about the green portal or the decoy portals helped me to learn that people are naturally curious...or afraid of the consequences.
The one positive reaction my failed usability testing gave me (before all those annoying little glitches) was the idea to add a "repeat the riddle" option in the second level for those who didn't catch it the first time. Hopefully I can add that without the entire program exploding.