ReviewDecisions , Decisions , Decisions : Choosing a

might be measured on a single scale. In human applica-New York, New York 10003 tions this measure is provided by 'utility'—a somewhat artificial and uncomfortable concept: In biology, Darwin-ian fitness provides a natural and genuinely one-dimen-Behavioral ecologists argue that evolution drives ani-sional scale. " mal behavior to efficiently solve the problems animals By anchoring economic theory to Darwinian notions of face in their environmental niches. The ultimate evolu-fitness, these behavioral ecologists undertook to explain tionary causes of decision making, they contend, can the ultimate causes of human and animal behavior. be found in economic analyses of organisms and their Whether a moose decides to eat algae or grass on a environments. Neurobiologists interested in how ani-particular day (Belovsky, 1984), with whom a monkey mals make decisons have, in contrast, focused their decides to mate (Dunbar, 1984), or whether a young efforts on understanding the neurobiological hard-salmon decides to forage or hide (Bull et al., 1996) can ware that serves as a more proximal cause of that all, these scientists contend, be viewed as decisions same behavior. Describing the flow of information which are the products of evolution acting to maximize within the nervous system without regard to these fitness in the face of uncertainty. Behavioral ecologists larger goals has been their focus. Recent work in a explain behavior in evolutionary terms by quantitatively number of laboratories has begun to suggest that analyzing the decisions animals make and correlating these two approaches are beginning to fuse. It may the outcomes of those decisions with theoretical or em-soon be possible to view the nervous system as a pirical measurements of fitness. Their goal is to relate representational process that solves the mathemati-a theoretical assessment of what an animal should do cally defined economic problems animals face by with behavioral data about what animals actually do. making efficient decisions. These developments in the They try to understand what causes a behavior by under-neurobiological theory of choice, and the new schema standing the evolutionary constraints under which that they imply, form the subject of this article. behavior evolved. In contrast, neurobiologists devote their resources to Introduction understanding what causes behavior to occur in a more In the 1650s, Blaise Pascal puzzled over one of the most proximal sense. Neurobiologists seek to understand the complicated decisions faced by enlightenment philoso-mechanistic cellular processes by which the brain pro-phers: " Either God is or he is not, …