Reducing the use of disposable plastics through public engagement campaigns: An experimental study of the effectiveness of different types of message appeals, modalities, and sources

Using a representative survey with an embedded experiment among 1001 Hong Kong residents, this study aims to provide empirically derived strategies for effective public engagement campaigns to reduce plastic pollution. Specifically, this study employed a 2 (frame:
gain vs. loss) * 3 (modality: text vs. image vs. infographic) * 2 (source: government vs. NGO) experimental design to (1) assess the attitudes, knowledge, and past behaviours of Hong Kong residents regarding the environmental impact of single-use plastics, and identify distinct segments that can be targeted by public campaigns; (2) analyze media use habits of Hong Kong residents and determine effective ways of reaching the above segments of Hong Kong residents with pro-environmental messages; and (3) examine the effectiveness of different types of message frames (gain vs. loss), media modalities (text vs. image vs. infographic), and information sources (government vs. NGO) in reducing the use of disposable plastics and encouraging re-use and recycling.

A series of analysis of variance (ANOVA) tests were conducted to determine the effect of message frames, modality, and information source on behavioral intentions. The results indicated that participants exposed to messages with loss frames (M = 5.14, SD = .897)
and those exposed to gain frames (M = 5.01, SD = .950) reported higher intentions than control group (M = 4.89, SD = .923; F(2, 998) =3.91, p < .05). Meanwhile, compared with image-based messages (M = 4.96, SD = .895), text-based (M = 5.15, SD = .930) and infographic-based messages (M = 5.13, SD = .926) were more effective in increasing people’s intention to reduce single-use plastics use (F(2, 917) = 3.91, p < .05). Information source, however, did not show significant difference in affecting people’s intentions (Mgov = 5.11, SDgov = .886; MNGO = 5.05, SDNGO = .963; t = 1.03, p > .05).

Based on respondents’ environmental concerns and their disposable plastics use habits, the data were then subjected to a cluster analysis to produce three distinctive segments of the population, the passive cluster (n =375, Mconcern = 4.97, Mhabit = 4.40), the moderate cluster (n = 403, Mconcern = 5.27, Mhabit = 3.10), and the concerned cluster (n =223, Mconcern = 5.57, Mhabit = 1.99). To gain further insights regarding the campaign strategies aimed at the passive cluster, a series of analysis of variance (ANOVA) tests were conducted and the results indicated that compared with the control group, both loss frame and gain frame were more effective in persuading the passive cluster to refrain from using single-use plastics. Meanwhile, text-based and infographic-based messages were more effective than image-based messages. Information source did not show significant difference in affecting behavioral intentions of the passive cluster. It also demonstrated that compared with the control group, the loss frame would be mostly effective for passive group when it was conveyed by text with NGO source (B = .376, SE = .185, p < .05 ), while the gain frame is most persuasive when paired with infographics and NGO source (B = .501, SE = .243, p < .05).