This thesis by publication incorporates three papers that address ongoing debate about the influence of social and individual level factors on sustainable consumption. Comprehensive yet parsimonious conceptual frameworks were developed for each of the papers pulling together extant gaps from social marketing and sustainable communication literature. The first paper investigates the influence of three major types of social norms on moral obligation to buy a sustainable product, taking in-group and environmental identity into consideration. The second paper investigates the influence of inspiration and in-group identity on purchase intention of a sustainable product. The third paper examines the effects of in-group framing and social comparison on the intention to increase number of sustainable actions. The frameworks have undergone an extensive validation process, including quantitative assessment using randomised controlled online experiments. Based on our findings across three studies, the sustainable messages will be most effective when emphasising: (a) both injunctive and descriptive norm appeals, (b) appealing to salient group identity, (c) feeling inspired by the behaviour of the reference group, and (d) upward comparison in a negatively framed social message. The results of our research extend previous research, providing insights into sustainable consumption and practical implications for social marketers in promoting sustainable behaviour with their marketing efforts. In particular, this research indicates that: (a) combined social norm appeals increase intention to purchase a sustainable product contingent on strength of environmental identity and in-group identity (paper I), (b) inspiration has a mediating effect on the relationship between combined social norm appeal and intention to purchase a sustainable product sooner (paper II), (c) social comparison has a moderating effect on the relationship between in-group framing and intention to increaser number of sustainable behaviours (paper III). Understanding the effects of novel moderators such as environmental identity, in-group identity (paper I) and social comparison (paper III) on the relationship between social norm appeals and behavioural uptake as well as investigating the effects of novel mediators of that influence adds further contributions (paper II) of this thesis. The results of the third paper show an important factor in overcoming the negative effects of upward comparison to other relevant group members - positively framed descriptive norms message. The findings extend previous research, providing insights into sustainable consumption. In addition, when consumers experience downward social comparison, framed messages do not create a significant increase in consumer‘s behavioural uptake of sustainable intentions. Finally, this research demonstrates that the use of salient identities for positive and negative in-group framing participants can help marketers and public policy managers to increase levels of sustainable consumption.Thesis (Ph.D.) -- University of Adelaide, Business School, 202
