  It may be tempting to see the infant’s ability to add and subtract the number of objects in a display as evidence that infants already have something close to the adult concept of number, but a series of studies suggests that this is not the case. Most telling is the extremely limited set size (about 3 objects) over which the baby can add or subtract. To illustrate this set size limit, which has emerged in a variety of experiments, consider the following study that used crawling, rather than violation-of-expectancy, as an indicator of the baby’s representation (Feigenson &amp; Carey 2005). In this study, babies watched as graham crackers were placed, one at time, into 2 separate boxes. The babies were then allowed to crawl to the box of their choice and retrieve the crackers. When one box had 1 cracker and the other box had 2, babies crawled to the box with 2. Similarly, when one box had 3 crackers and the other had 2 or had 1, they crawled to the box with 3. The surprising finding, however, is that babies failed with 4 versus 3, 4 versus 2, and even 4 versus 1. Apparently, the ability to represent and keep track of exactly 4 objects is beyond the baby’s capability. Given the set size limit of 3 objects, it is arguable that the baby’s competence should be understood as an ability to track 3 different objects in working memory. One might argue that the baby can succeed in adding and subtracting very small numbers of objects without having a general concept of number or any general numerical competence. We return to this issue in section 2.3.