The American Academy of Pediatrics (1999, 2011) recommends no screen time for children under two years and limited screen time for three-and four-year-olds. Despite these recommendations, most young children have easy access to various types of screens. In particular, children's use of mobile media, including tablets and other touch screen devices, is increasing (Common Sense Media, 2013). Even though scholars have highlighted positive uses for mobile media (Christakis, 2014; Radesky, Schumacher, & Zuckerman, 2015) and there are recommendations in place for using mobile media with young children in active, open-ended ways (NAEYC & Fred Rogers Center, 2012), there has been very limited research conducted on the impact of mobile media on young children's development. What is more, as early childhood professionals are beginning to incorporate mobile media into their classrooms, they are struggling with the ability to use these devices in developmentally appropriate ways (Marklund, 2015; Nuttall, Edwards, Mantilla, Grieshaber, & Wood, 2015). The primary purpose of the present study was to examine the efficacy of using different types of mobile media apps to increase the receptive and expressive vocabulary development of preschool children living in economically disadvantaged communities. Children and teachers in four Head Start classrooms participated in the quasiexperimental study, which included an eight-week intervention in which the children interacted with one of two types of apps: one classroom used direct instruction vocabulary apps (n = 16) and one classroom used open-ended vocabulary apps (n = 15). Two classrooms served as control groups (n = 18; n = 14) which used apps that were Kushner, Stephanie Propst, Brooke Rusoff, Rachel Sherman, and Cathy Twyman for your professionalism, flexibility, and enthusiasm for assessment. In particular, thank you viii to Amanda Barnes, whose eagerness to learn about research was inspiring and who went above and beyond to ensure the quality of my data. I am forever grateful to my mentors, committee members, and UCF ECDE family. Thank you to Lap Nguyen, who embarked on this PhD journey with me and helped me to realize when it was time to take a break. I am grateful to Dr. Judit Szente who encouraged me to enroll in the PhD program, supported publication efforts, and was always willing to assist me. Thank you to Dr. Judy Levin who believed in me throughout my undergraduate, masters, and doctoral careers and who, despite being the hardest working person I know, was never too busy to listen. Thank you to Dr. Debbie Hahs-Vaughn for her expertise in statistics and always finding time to assist when I needed guidance. Thank you to Dr. Rex Culp for his encouragement and enthusiasm. Thank you to Dr. Laurie Campbell for being a wonderful mentor and support system. I would also like to thank Ms. Jill Goodman for providing expert advice on the apps chosen for this study and guiding me in the development of the iPad assessments and intervention plans. Finally, thank you to my chair, Dr. A...
