This paper contrasts a picoeconomic approach to theexplanation of akrasia with Davidson's divided-mind approach and defends theformer in a wider context. The distinctive merits of a picoeconomic model of mindlie in the following aspects: First, it relies on a scientifically well-groundeddiscovery about motivational dynamics of animals for its explanation of preference change,which elucidates or materializes some philosophers' speculations both about thepossible mismatch between valuation and motivation and about the relevance of temporalfactors to akrasia. Second, it grounds the necessity of endogenous (...) higher-order constraints,expressible in forms of judgment, in an intrapersonal dynamic process of interactivefirst-order temporary preferences. Thus the motivational basis for the normativeconstruction of the rationality of `best judgment' can also be illuminated with this model. (shrink)