This dissertation encourages adoption of a message-oriented receiver perspective when developing new instructional communication theories and proposes a causal-process model derived from Knowledge Acquisition Theory to demonstrate how this perspective can be used to predict student cognitive learning outcomes. Three hypotheses are generated to test the propositions of the derived model. The first hypothesis seeks to determine which dimensions of instructional message clarity and course content relevance best predict student interactions with instructional content. The second hypothesis predicts that student self-reported knowledge gains are a function of student interactions with content. The third hypothesis predicts that a significant proportion of the variance in knowledge gains can be explained by the combination of message characteristics with student content interactions both in and outside the classroom. A cross-sectional survey research design was used to collect responses from undergraduate students at a large southern public research university (n=333). The hypotheses were tested using linear and hierarchical regression and results demonstrated statistical support for all three hypotheses. The first hypothesis revealed the dimensions of instructional message clarity and course content relevance that significantly predicted student interactions with content inside and outside of class. Support for the second hypothesis illustrated that both in class and out of class content interactions significantly predicted student self-reports of knowledge gains. Finally, hypothesis 3 tested the comprehensive causalprocess model derived from Knowledge Acquisition Theory. The derived model received strong support and ultimately accounted for 65% of the variance in student perceptions of knowledge gains. Student perceptions of knowledge gains increased when students perceived textbook messages as clear, course goals and expectations as clear, content as relevant to their own lives, and when students enacted knowledge acquisition behaviors outside of class. Surprisingly, in class content interaction, presentation clarity, and procedural clarity dropped out of the model. Implications and limitations of the present study are discussed, directions for future research are suggested, and a persuasive argument is presented for why instructional communication researchers should continue to develop a message effects research agenda supporting the development of strong instructional communication theories that produce practical results to inform educational practices.