Cognitive euroscience: scalar variability in price estimation and the cognitive consequences of switching to the euro.

The present paper examines the ability to evaluate prices in a familiar currency (French francs, Portugese escudos, or Irish punt) and in an unfamiliar currency (euro). Participants evaluated prices for different items either by selecting the most appropriate price from a set of alternatives (in a timed or not-timed version) or by directly producing a price estimate for each item. The results followed Weber's law: The standard deviation of estimated prices was proportional to their mean. The Weber fraction was stable for the familiar currency in different countries, but was significantly higher for the unfamiliar currency. We suggest that price estimation relies on a learned mapping between items and their prices as represented by distributions of activation on an internal number line. The observed Weber fraction reflects the degree of expertise with a given currency as well as a minimal variability intrinsic to the number line itself.