  If current thinking about these systems is on the right track, we have two innate systems, each of which deals with number in some sense. The analog system takes a range of perceptual presentations and assigns an ordering by relative magnitude. The second system identifies and tracks (a limited number of) discrete elements in an environment. A current research question that is of particular interest to philosophers is this: what is the relation of these innate systems to the adult concept of number. Notice that the analog system does not get us to the concept of an exact number. Only ranges are detected—the system can judge that two sets are in the same range (below the ratio-threshold for discrimination), but two arrays that are “the same” in this way need not have the same number of elements. The second system is not approximative. If the subject has tracked 2 objects and 1 is added, as in Wynn’s studies, the difference is noted and the subject’s expectations change accordingly. So this object-tracking system is sensitive to the number of units in play, and in this respect is closer to the adult notion of number. But it has an extremely constricted range, and is useless when it comes to problems that extend beyond its range. The crawling infant in the study cited earlier doesn’t represent an added 4th cracker as one more than the 3 previously tracked. The infant doesn’t even track the 4th element: the system seems to (eccentrically) shut down completely when its range is exceeded. So the concept of number—the successor function and all that it brings in its wake—is not implemented in this system.