Thanks for the replies. Today we tried praising him for eating without spitting and ignoring the spitting. We just stopped feeding him and stepped away for a few minutes. I'm pretty sure it's just a phase, as he does seem to get stuck on one thing for several days (tongue clicking, lip popping, etc) so we'll just hope it goes away. BTW, does anyone know at what age they do start to understand "no" or at least the tone of voice?