It's already extremely well established that people will work far beyond what they need to maintain basic necessities. There are all sorts of strong motivations for humans outside of basic survival. In addition if you look at groups with steady income streams and no perverse incentives (ex. retirees, trust funders) the vast majority remains productive in some capacity. If you are making the claim that UBI would so drastically change human behavior as to invalidate all this observed behavior than the burden of proof should be on you.