But smart people might conclude some specific individual is stupid because of consistently erroneous patterns of thought and analysis which do not improve with experience. There are a few individuals who I've spoken to on a variety of topics over the course of years who, as a rule, develop beliefs based on sketchy evidence and then retain those beliefs even in the face of mountains of contrary evidence. Even when they hold essentially the same views as I do, it's often for bad reasons; there isn't really a coherent thought process or a body of evidence that got them to that point. Such people really are stupid.