This study investigated middle school students' Artificial Intelligence (AI) literacy, focusing on cognitive and affective dimensions with regard to learning about AI. Fourteen middle school students participated in a five-day summer camp. They engaged in a project-based AI literacy program with hands-on activities, data collection and modeling, and group projects and presentations. For the cognitive dimension of learning about AI, the students' conceptual understandings of AI and their applied reasoning skills in AI-infused problem-solving were investigated. For the affective dimension, attitudinal aspects relating to learning about AI were studied based on the expectancy-value theory. For this study, multiple-choice tests, proposal planning worksheets for constructed responses, a survey questionnaire, and an interview protocol were developed and employed to measure or capture the students' conceptual understandings of AI, applied reasoning with AI, and productive dispositions with learning about AI, respectively. The study confirmed the efficacy of the project-based AI literacy program through both cognitive and affective gains. First, the students' understanding of AI concepts significantly increased after the intervention, as the pre- and post-tests suggested. Social semiotic multimodal analysis of the student artifacts as well as project development and presentation revealed that they were able to apply AI concepts in their collaborative problem-solving for their school community. This qualitative analysis provided detailed evidence of learning and areas for improvement in AI literacy. Secondly, regarding the affective dimension, the pre- and post-surveys demonstrate that the project-based AI literacy program was effective in increasing the students' productive dispositions, specifically their ability beliefs and task values toward learning about AI. The student focus group interview supported the increase in the productive disposition scales, and the student reflections are presented with interpretation. From these findings, implications for designing student-centered AI literacy education were derived, including ways to augment students' cognitive engagement with AI concepts and tools as well as productive dispositions to motivate and sustain student learning. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]