Legal scholars increasingly rely on a behavioral analysis of judgment and decision making to explain legal phenomena and argue for legal reforms. The. main argument of this new behavioral analysis of the law is twofold: (1)All human cognition is beset by systematic flaws in the way that judgments and decisions are made, and theseflaws lead to predictable irrational behaviors and (2) these widespread and systematic nonrational tendencies bring into serious question the assumption of procedural rationality underlying much legal doctrine. This Article examines the psychological research relied on by legal behavioralistst o form this argumenta nd demonstratest hat this research does not support the bleak and simple portrait of pervasivei rrationalityp ainted by these scholars.C areful scrutiny of the psychological research reveals greater adherence to norms of rationality than that implied by the legal behavioralists, and the methodological and interpretive limitations on this psychological research make extrapolation from experimental settings to real world legal settings often inappropriate. Accordingly, this Article argues that legal scholars should exercise greater care and precision in their uses of psychological data to avoid advocating further legal reforms based on flawed understandings of psychological research.