Introduction to the spillover effectThe aim of this chapter is threefold. Firstly, the chapter aims to introduce the term 'spillover' and its different conceptualisation, as well as providing an overview of current research developments. This chapter will overall provide the reader both a broad understanding of the different concepts of the spillover effect alongside its implications for environmentally friendy behaviours in the workplace.Secondly, the chapter aims to give an overview of underlying factors that influence spillover and a discussion of how the spillover effects might influence social marketing campaigns and behavioural change programmes that promote pro-environmental behaviours in organisations. Finally, the chapter aims to assess the methodological approaches used to investigate spillover effects, inclusive of quantitative, qualitative and mixed methods.The psychological concept of spillover could be simply understood as the flow and propulsion of cognitive thoughts, emotions or actions from one area to another. In relation to the latter aspect, Nillson et al. (2016: 1) consider that "the spillover effect proposes that engaging in one behavior affects the probability of engagement or disengaging in a second behaviour". The idea of the spillover effect is not new and has been applied in a number of areas such as knowledge (Acs et al., 2009), emotional conflicts between the workplace and the family (Grunberg et al., 1998; Westman, 2002) and health behaviour (Dolan and Galizzi, 2014). More recently, research in the fields of ethical marketing and environmental psychology has been investigating the spillover phenomenon in the context of sustainable lifestyles; here an increasing interest in understanding secondary behaviour
Cognitive dissonance and self-perception theoryAccording to cognitive dissonance theory (Festinger, 1957) people experience discomfort when holding two contrasting cognitions and are motivated to reduce the psychological uneasiness they experience. This can be achieved in a number of ways, including changing attitudes, behaviours, externalising responsibility or reducing the importance of dissonant elements (Gregory-Smith et al., 2013). In the pro-environmental context, this means a person holding pro-environmental views but acting unsustainably will experience a psychological discomfort. This may be reduced by acting in an environmentally-friendly way (Thøgersen, 2004). Therefore, the need for consistency might lead to positive spillover between environmentally-friendly behaviours and between settings. Inconsistent