Do Perceived Message Effectiveness Ratings Change in Response to Repeated Message Exposures?

Perceived message effectiveness (PME) is used in message pre-testing and as an indicator of campaign receptivity. Studies have yet to examine whether PME changes in response to repeated exposures to messages and whether the pattern of change differs for effects perceptions (i.e., perceived impact of messages on intended outcomes) versus message perceptions (i.e., judgments of a message's ability to foster message processing). To address these gaps, we conducted a 3-week randomized clinical trial (RCT) with parallel assignment among 1,514 US adolescents aged 13-17 years who were susceptible to vaping or used e-cigarettes in the past 30 days. Repeated exposures to vaping prevention video ads over time increased both effects perceptions (<i>p</i> < .001) and message perceptions (<i>p</i> < .05), with a larger mean increase for effects perceptions than message perception (mean difference of .32 vs .05). Our findings suggest that effects perception measures are more likely to change in response to repeated message exposures over time. Understanding distinct patterns in PME following repeated exposure could help researchers better interpret PME data in both formative and process evaluations, particularly for health campaigns aimed at behavior change.