Is five years long enough to get a real reaction? Unless somebody is on the verge of retirement, and they want to keep working after the experiment, they must consider staying in the job pool or have difficulty getting hired in five years. To see how people would react to a government-provided basic income, which would presumably be fore life, the study may have to emulate that more perfectly.
Nevertheless, I'm very excited by this project and seeing what comes of it.
Does the basic income prevent people from doing work? Or from doing work they hate?
A correctly designed study will attempt to teach the participants to (1) have basic spending/expenses that match their income (2) procure the basic income from already-available sources (e.g. food stamps, subsidised health care, social security...) and (3) form income-pooling groups that provide/insure a basic income for their members. All three have already been done at a small scale. 100s of people in the United States currently practice #3, e.g. Federation of Egalitarian Communities. 1000s of people practice #2, e.g. Puna Hawaii or your local trailer park.
I think basic income would have the effect of insurance, to allow individuals to take bigger risks and follow their dreams more.
Nevertheless, I'm very excited by this project and seeing what comes of it.