I'd say that's an extremely crude understanding of what computers can actually model. There are ways that humans stream through thoughts that depend on tacit knowledge and unconscious connections, and there's no reason why those can't be modeled by a computer. And the equilavence betweeen "rational" (in some informal, human sense of the term, as in talking out loud like spock), and "computable" is just a misunderstanding. Computable contains much more than this naiive conception of what is rational.