  If one steps back from the theoretical heat of the Empiricist-Nativist debates, it should not be surprising that we have an innate system for discriminating sets by their approximate size, and that this system is found in other animals too. Animals typically need to take some measure, for example, of the relative size of food sources, of the relative number of predators on their left and right flanks, and so on. In some animals, these abilities may be part of an encapsulated system devoted to a specific task. The bee’s awareness of the relative size of a discovered food source—information communicated in the scout’s dance—is a popular example of this sort of ability (Frisch 1953). In other animals, the system operates more broadly, and different sorts of inputs can be measured in this way (heard sounds, perceived jumps, and so on). It is as if the brain has an ‘accumulator’; a bar graph system of some kind that maps input arrays into some neutral format and appends the elements together into a stack, and a scanner that judges relative stack size. Gelman and Gallistel and others have explored such systems extensively (starting with Gelman &amp; Gallistel 1978).