Next best step decisions in clinical practice are grounded in systematic clinical reasoning processes that integrate pattern recognition (System 1 thinking) with analytical deliberation (System 2 thinking). Understanding how clinicians process clinical information is essential for developing sound decision-making and avoiding diagnostic error. The hypothetico-deductive model describes how clinicians generate and test diagnostic hypotheses. Upon encountering a clinical presentation, the clinician rapidly generates a limited set of diagnostic possibilities (usually 3-5) based on the chief complaint, key history features, and initial vital signs. Subsequent data collection (focused examination, targeted diagnostics) is designed to confirm or exclude these hypotheses. This model is efficient but vulnerable to cognitive biases: anchoring bias (fixating on the initial hypothesis and ignoring disconfirming evidence), premature closure (accepting a diagnosis before sufficient data is gathered), and availability bias (overweighting diagnoses that are recent, memorable, or emotionally salient). Clinical decision rules (CDRs) are evidence-based scoring systems derived from large patient cohorts that standardize decision-making for specific clinical scenarios. They reduce cognitive bias by providing objective criteria. Examples include: Wells criteria for PE/DVT (assigns points for clinical features to...