This article offers a definition of involvement based on a spreading activation model of human memory processing. Involvement is viewed as the spread of activation through working and long-term memory. Topics resulting in more extensive and/or stronger activation result in higher involvement. As a first test of the definition offered, an experiment was conducted to explore the effects of involvement and limited prior knowledge on cued recall and recognition memory for elements of persuasive messages common in investor relations. Evidence from the measurement of reaction time for recognition supported the model. Theoretical and practical implications of the differences in the effects of prior knowledge and involvement on different types of memory performance are discussed.