Within western societies the act of consumption is not merely concerned with satisfying basic human needs. Rather, consumption has become a source of leisure and self expression for the masses (Belk, 1988). This has meant that humankind’s wants have tended to outstrip the world’s finite resources available, leading to environmental damage, questionable farming practice and the widespread abuse of human labour. In response to these issues the phenomena of ethical consumption was born. Ethical consumption attempts to limit the environmental, human and animal costs of our spending via the favouring of products that are deemed to be for the betterment of wider society. At face value ethical consumption has been hugely successful in terms of market share, with sales of products stressing their ethical credentials having grown rapidly in recent years (Cooperative Bank 2011). However, despite this success, ethically branded products still represent a minority of purchases (Thøgersen, 2006). Psychological research exploring the reasons why consumers purchase ethically is dominated by papers focusing upon consumers’ attitudes, values and intentions (Andorfer & Liebe, 2012, Milfont & Duckitt, 2004). However, consumers’ attitudes do not always mirror actual spending (Auger, Burke, Devinney & Louviere., 2003; Auger & Devinney, 2007). Whilst one third of consumers describe themselves as being ethical spenders, only 1-3% of products purchased are Fair Trade certified (Cowe & Williams, 2000). The divergence between attitude and behaviour has been referred to as the ‘ethical purchasing gap’ (Andorfer & Liebe, 2012, Clayton & Brook, 2005). One factor that may be partially responsible for the divergence between purchase intention and actual behaviours is self-regulatory fatigue (ego depletion). Chapter one of the thesis presents the argument for ethical spending being affected by, amongst other things, our ability to suppress our impulsive desires via a process known as self-regulation (Bagozzi, 1992; Baumeister, 2002; Baumeister & Vohs, 2007). According to the self-regulatory fatigue literature, self-control requires the expenditure of blood glucose (Gailliot, 2008, Inzlicht & Gutsell, 2007). However, the available level of blood glucose temporarily diminishes with continued use of the self-regulatory system. In response to the lower availability of blood glucose, individuals begin to limit all non-essential cognitive expenditure, including further acts of self-regulation. Individuals who have exhausted their capacity for self control are said to be ego depleted or in a state of self-regulatory fatigue (Baumeister & Heatherton, 1996; Hofmann. Friese & Strack, 2009; Muraven & Baumeister, 2000) Chapter one argues that self-regulatory fatigue may restrict an individual’s capacity to consider the social and long-term impacts of their spending to resist the temptation of cheap consumer goods. As a result, it is predicted that ethical spending may be negatively affected by self-regulation fatigue. Following this theoretical foundation, Chapter two presents the methodological rationale for the research project that set out to test various aspects of this foundational hypothesis. Chapter three presents the findings of the first empirical study. The purpose of the study was to use open-ended questionnaires to explore the principles that guided participants’ spending, as well gaining an insight into instances where there was a discrepancy between spending and principle. The study is included within the thesis primarily to show the genesis of the research agenda. The study indicated that consumers within the sample were primarily concerned with traditional forms of ethical consumption, namely environmental, human and animal welfare concerns. Participants justified non-principled purchasing as being a result of financial consideration or impulsive urge. It was thus decided to explore the possibility that self-regulation fatigue may have a potentially negative impact upon ethical spending, due to its known relationship with impulsive spending (Vohs & Faber, 2007). Chapter four explores the effects of self-regulation fatigue upon socially-minded economic behaviour within the controlled setting of a social dilemma game. Ethical consumption can be considered to be a prime example of a ‘social dilemma’ in the sense that decisions relating to whether or not to consume ethically involve a direct conflict between an individual’s short term interests (e.g. to save money) and the collective interests of wider society (Gattig & Hendrickx, 2007; Milfont & Gouveiac, 2006). Therefore it was decided to measure the effects of self-regulatory fatigue within an experimental social dilemma task. The task used was based upon the forest game, which was first outlined by Sheldon and McGregor (2000), with the white bear thought suppression task (Wegner, Schneider, Carter, & White, 1987) being utilised to manipulate self-regulatory fatigue. The results revealed a clear divergence in behaviour within the game as a function of the manipulation of self-regulatory fatigue, with non-depleted groups sustaining the central resource longer than their depleted counterparts. Chapter five builds on the findings of chapter four through an exploration of the relationship between ego depletion and participants’ willingness to pay for ethical goods. The study utilised a discrete choice measure in order to measure participant’s willingness to pay for ethical goods. The findings did not show a significant effect of self-regulatory fatigue on the willingness to pay for ethical goods. However a potential explanation for this result was the fact that the decision-making processes involved in this study were less arduous than those required within a real-life shopping environment (or, for that matter, than the decisions required in the forest game reported in chapter four). It is possible that the complexity of the choice presented may have been insufficient for the decision to be negatively affected by self-regulatory fatigue. The study is thus included in order to illustrate the importance of utilising more realistic measures of spending that incorporate more of the complexity of decision-making required in real-world contexts. Chapter six presents four separate experiments exploring the relationship between self-regulatory fatigue and ethical spending. The first study utilised an online supermarket simulation and asked participants to go shopping for one week’s worth of groceries after either completing, or not completing, the white bear thought suppression task. The simulated supermarket allowed participants to select from a range of over 1900 products. The pattern of results indicated that participants in a state of self-regulatory fatigue spent significantly less on ethically branded products than their non-depleted counterparts. However, this was only true for individuals with a high food budget. Those with a low budget were not significantly affected, presumably due to having relatively little flexibility in terms of product choice and/or having established shopping habits focusing upon value. The second study in chapter six explored the ways in which social appeals interact with self-regulatory fatigue. Participants were presented with an attention control task before reading either an article praising students for their ethical behaviours or a control article. Participants were then asked to “go shopping” within the online store. Results once again indicated that self-regulatory fatigue reduced spending on ethically branded goods. However, contrary to predictions, the social appeal had no significant effect on levels of ethical spending either as a main effect or in interaction with self-regulatory fatigue. The study also explored the effect that self-regulatory fatigue had upon the relationship between behavioural intentions and subsequent ethical spending behaviour. The findings revealed that behavioural intention was shown to predict ethical spending only at times when self-regulatory fatigue was low. When self-regulatory fatigue was high, the frequency of previous ethical purchasing was shown to be a more important determinant of ethical spending than behavioural intention. The third study further investigated the influence of self-regulatory fatigue on ethical spending by comparing the effects of an article stressing the fact that engaging in ethical spending would bring social approval with an article stressing that ethical spending was an individual’s personal responsibility. Chapter six sets out the argument that since personal norms are internalized appealing to an individual’s sense of personal responsibility, they may have a relatively automatic influence upon individual’s behaviour. In contrast, social approval may have less influence under the influence of ego depletion as it requires the consideration of others points of view (Moore and Loewenstein, 2004). The analysis revealed a marginally significant interaction between self-regulation fatigue and article type in relation to rates of ethical spending. At times of high self-regulatory fatigue, stressing personal responsibility appeared to be more effective in increasing ethical spending than stressing social approval. The final empirical study in the thesis aimed to explore the impact of self-regulatory fatigue on ethical purchasing in a real-world context by comparing shopping receipts with self-reported levels of self-regulatory and mental fatigue during actual supermarket shopping trips. The results indicated that self-regulatory and mental fatigue did indeed have a negative impact upon ethical spending and this effect was detectable even in the face of the increased background noise that is associated with taking such measures in a naturalistic context rather than in the lab. The final chapter of the thesis integrates all of these empirical results and considers their potential implications, limitations and the directions that they offer for future research. The thesis concludes that under the specific circumstances, where consumers have some discretion over their spending, self-regulatory fatigue has a negative effect upon consumers’ rates of ethical spending. The findings suggest that to fully understand ethical spending researchers are required to consider the economic, habitual and social psychological factors (such as attitudes and levels of self-regulatory fatigue) that may be involved. However, the relationship between self-regulation and ethical behaviour, identified for the first time in the current research, represents an exciting finding and a potential building block for future research in this area.