Vincenzo Crupi (Turin) gives a talk at the MCMP Colloquium (16 April, 2014) titled "Models of rationality and the psychology of reasoning (From is to ought, and back)". Abstract: Diagnoses of (ir)rationality often arise from the experimental investigation of human reasoning. Relying on joint work with Vittorio Girotto, I will suggest that such diagnoses can be disputed on various grounds, and provide a classification. I will then argue that much fruitful research done with classical experimental paradigms was triggered by normative concerns and yet fostered insight in properly psychological terms. My examples include the selection task, the conjunction fallacy, and so-called pseudodiagnosticity. Conclusion: normative considerations retain a constructive role for the psychology of reasoning, contrary to recent complaints in the literature.