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Date of Award


Document Type

Thesis-ISU Access Only

Degree Name

Master of Science (MS)


School of Communication

First Advisor

Daniel C. Davis


This thesis investigates how communication and design of persuasive health messages influence people's attitude, intention, and dietary habits in relation to a scientifically proven disease prevention diet: the whole-grains, plant-based diet. The discussion of plant-based diet addressed the medical, nutritional, psycho-ethical, sociological, and environmental concerns. The Extended Parallel Process Model (EPPM) is a communicative framework using fear and danger appeals to provide danger prevention alternatives, thus helping people to adopt new behaviors. The application of the EPPM will further analyze how communication messages can motivate and convince people in adopting a plant-based diet.

A quantitative and qualitative data collection process was conducted to analyze the usefulness of the EPPM for promoting the whole-grains, plant-based diet (Fehrenbach, 2015; Witte & Allen, 2000). Quantitative research participants were assigned randomly to one of the five groups with varied threat and efficacy message parameters and filled out an immediate post-test survey about danger control (i.e., attitude, intention, and behavior) and fear control outcomes (i.e., perceived manipulative intent, message derogation, and defensive avoidance). Survey participants were contacted again after one weeks to take a Time 2 survey for tracking actual behavioral changes. One-Way ANOVA and MANOVA were used in testing the significance of threat and efficacy in health messages. This thesis focused on implications of the findings for optimal rhetorical design of persuasive messages about plant-based diets.


Imported from ProQuest Cheong_ilstu_0092N_11127.pdf


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