People NEVER change their behavior without either - a proverbial sword of Damocles hanging above their heads OR a big carrot on the end of a stick.

The problem with small scale tests of UBI is that it doesn't effect the majority's thinking about work and income. Everyone knows it is just 1) a test, 2) small, 3) doesn't change the cultural norms. As long as those things apply, the test is meaningless. Just like the 'stimulus' payments have a small short term impact individually, they don't change the culture: people don't change their long term behavior for short term gains.