I only know the basics of Buddhism (and I really love and respect the teachings I do know). But from what I understand, Karma could be seen as this reward. Also the ultimate goal is to reach the reward of Nirvana. One could also argue that having to be reincarnated because a soul did not reach enlightenment would be an example of negative reinforcement “you have to keep trying in this imperfect world until you get it right”. But like I said, I only know the surface. Buddha is very wise and may have spoken in this.