From NYmag's Science of Us blog:
As all that history implies, basic income serves as a Rorschach test for your account of human nature. If given the chance, will people be as lazy as possible? Will they abandon work? Or will having security enable them to contribute, rather than take, from social resources? Are the poor impoverished because of their lack of effort and competence or because of systemic, even unconscious disadvantage? The problem is that large-scale, long-term, methodologically rigorous studies of basic income are yet to be done.
Still, the evidence that’s already out there looks good.