Hannula and Lehtinen (2001, 2005) defined spontaneous focusing on numerosity (SFON) as the tendency to notice the relatively abstract attribute of number despite the presence of other attributes. According to nativists, an innate concept of one to three directs young children's attention to these “intuitive numbers” in everyday situations—even before they acquire language. If so, their tendency to attend to two and three should be comparable. If language in the form of the first few number words facilitates the construction of these number concepts, then toddlers' tendency to focus on two and three should parallel the staggered development of verbal number skills. The present study is the first to systematically examine if and how the size and makeup of a collection affect toddlers' tendencies to focus on number. For each of two types of attention tasks, each of 37 participants between the ages of 2 and 4.25 years old was shown 36 different collections of 2, 3, and 4 items that were homogeneous, semihomogeneous (the same shape but two different colors), or heterogeneous (two different shapes and two different colors). Age, size, and makeup had a significant effect on participants' tendency to attend to number. The significant drop off in this tendency with collections of more than two items is inconsistent with the nativists' hypothesis of an innate cardinal concept of three.