This research is part of the summative evaluation of the CPB-PBS Ready To Learn Initiative, which is supported by the U.S. Department of Education and seeks to develop engaging, high-quality educational programming and supports for two- to eight-year-old children living in low-income households. During the 2010-2015 grant cycle, Ready To Learn aimed to deliver early mathematics resources on both established technologies (computers, video displays, and gaming consoles) and emerging digital platforms (tablet computers, interactive whiteboards, and smartphones) to create anytime-anywhere learning experiences. (author abstract)