Objective: There is insufficient evidence for the effectiveness of various tones of communication in modifying health behaviours. We examine the moderating role of assertiveness in the effect of positive/negative language on emotional responses (optimism, self-efficacy, and guilt), and resulting preventive health behaviours.
Design: Three experiments were employed. An online experiment tests the relationship between positive/negative language and assertiveness when people communicate about healthful eating. Next, a field study examines the moderating effect of assertiveness in positive and negative language encouraging using sunscreen among street passers-by. Third, an online study explores whether the effect of assertiveness in positive and negative messages on hand-washing intentions is mediated by increased optimism and self-efficacy, and decreased guilt, respectively.
Results: Positive language increases compliance when expressed assertively because the assertive tone emphasises optimism and self-efficacy. Conversely, negative communication is more effective when expressed non-assertively, because of the replenishing effect of the gentler tone on the guilt evoked by the negative communication.
Conclusion: Assertiveness serves as an intensifier of what is being communicated. When considering whether to employ positive or negative language in health messaging, assertiveness should be considered as part of the design of effective health communication strategies leading to health promoting behaviour change.
Keywords: Health communication; assertiveness; guilt; language; optimism; self-efficacy.