Sufficiency for sustainability: Determinants and strategies for reducing clothing consumption

This dissertation examines the psychological determinants for reduced clothing consumption, which is understood as one example of urgently needed behavioural change to mitigate climate change. It investigates how these determinants can be addressed with an intervention strategy to achieve a reduction in clothing items purchased by consumers. The overarching theoretical framework for this thesis is the comprehensive action determination model (CADM), and the dissertation comprises three articles, which successively contribute to the overall aim of identifying successful strategies for behavioural change. Paper I explores the normative part of the CADM in more depth and extends it with the role that identification with all humanity (IWAH) plays for the development of personal norms in a globalised consumption context. Paper II examines the applicability of the full CADM across different countries and reveals the relationship between the intention to reduce consumption and the actual number of items purchased. Paper III reports on an intervention strategy, which was developed based on the insight from Papers I and II and is aimed at encouraging reduced clothing consumption. The main findings of this thesis relate to insight about behavioural change and about intentions and personal norms, which in turn are hypothesised to influence behaviour. We find that it is possible to reduce the number of items purchased but that strategies aimed at increasing intention alone are not sufficient to induce such a behavioural change. In our study, goal setting, feedback, and commitment helped consumers reduce their clothing consumption. Moreover, personal norms were shown to be the strongest determinant for reduction intentions. Personal norms are strongly influenced by social norms (i.e. what relevant others are doing and expect one to do). They are related to problem awareness regarding environmental issues and the belief that one is able to alleviate these problems with one's behaviour. In multiple ways, the thesis contributes to the existing literature and delivers valuable insight for practitioners. First, a theory-driven intervention is tested in practice to identify successful avenues for reducing the consumption of clothing. Second, behaviour is measured in addition to measuring the intention to reduce clothing consumption, elucidating the intention-behaviour relationship and underlining the importance of strategies that help consumers translate their intentions into actions. Third, the role that IWAH plays for personal norm formation is examined. The existing norm activation model (NAM) is extended, which improves the understanding of personal norms in a context characterised by spatial and temporal psychological distance. Finally, previous cross-cultural studies are advanced by applying measurement invariance tests, and previous behaviour measurements are improved through the collection of diary data.