Psychological studies of early numerical development fill a void in mathematics education research. However, conflations between magnitude awareness and number, and over-attributions of researcher conceptions to children, have led to psychological models that are at odds with findings from mathematics educators on later numerical development. In this chapter, we use the approximate number system as an example of a psychological construct that would benefit the mathematics education community if reframed to account for distinctions between number and magnitude. We provide such a reframing that also accounts for the role of children's sensorimotor activity in the construction of number. [For the complete volume, "Constructing Number: Merging Perspectives from Psychology and Mathematics Education. Research in Mathematics Education," see ED616587.]