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In recent years, there has been a growing body of research on nudging and nudge interventions, which are cost-effective alternatives compared to traditional interventions such as tax incentives or other financial inducements. Nudges are small changes in the environment, triggering heuristic processes in individuals, which in turn lead to a particular choice of a behavioural option (Thaler & Sunstein, 2008). Nudges can appear in different forms, such as visual interventions. A prominent example are pictorial warnings on cigarette packaging (e.g., Sunstein, 2014; Noar et al., 2016). Pictorial warnings and the negative emotions they cause have been proven to be effective when it comes to the reduction of cigarette consumption (Thrasher et al., 2007). Often visual intervention nudges are depicted on the behavioural option that should be avoided, but we were interested if the visual nudges are also effective when depicted on the desired behavioural option, in our case the consumption of a vegan product. Thus, the planned study thematises the consumption of milk in chocolate. As the consumption of meat and dairy products is considered as one of the most harmful behaviours for the climate and environment (e.g. Gardner & Stern, 2008; Gerber et al., 2013), a reduction of dairy products induced by nudges are also of special interest in climate crisis. Pictorial warnings have proven to be more effective than text-only warnings when it comes to cigarette consumption (Noar et al., 2016). We assume the same effect for pictures and prompts informing about the consumption of dairy products and its consequences. However, there are inconsistent findings for the effect of positive and negative pictures. Some studies found negatively valenced information to be more effective to shape people’s behavior than positively valenced information (e.g. Chang & Lee, 2009; Levin et al., 1998), while some authors argue that information with a negative valence can have discounting or boomerang effects (e.g. Chang, 2007; Sunstein, 2014). Hence, we expect people who get presented with positively valenced pictures to differ from people who are presented with negatively valenced pictures in regard to their consumption decision, but the direction of the effect is not clear yet. The WHO (2014) recommends the combination of pictures with prompts. (Therefore, we present the pictures in combination with a prompt.

Nudges are small changes in the environment, triggering heuristic processes in individuals. This leads to a particular choice of a behavioural option (Thaler & Sunstein, 2008). A prominent example are pictorial warnings on cigarette packaging (e.g., Sunstein, 2014; Noar et al., 2016). Pictorial warnings and the negative emotions they cause have been proven to be effective when it comes to the reduction of cigarette consumption (Thrasher et al., 2007). In order to test the effectiveness of nudge interventions on the desired behavioural option instead of the option which should be avoided, we conducted an online experiment on the effect of pictorial nudge valence on people’s product choice. A preregistration of the online study including more detailed descriptions is available open access at https://osf.io/5k8zw/. The study tested the effects of a prompt in combination with positive and aversive pictorial nudges on people’s decision for vegan products. The desired behavioural option was a vegan chocolate and the alternative option was a milk chocolate bar. The study revealed that the combination of a prompt and a positive pictorial nudge on the vegan chocolate bar packaging caused people to choose the vegan product more often than people who only got presented with a blank vegan chocolate bar packaging. The present field experiment aims at replicating the effect of the combination of a prompt and positive pictorial nudge on people’s real choice of vegan products.

Truelove and Parks (2012) investigated misconceptions on behaviours related to climate-change among U.S. students. They found that participants overestimated the impact of littering, but underestimated the impact of meat consumption and adjusting the thermostat. It is unclear, how much knowledge the German public has about behaviours related to climate-change. This study investigates what a German sample knows about the impact of behaviours to mitigate global warming. Additionally, we investigate if there is a relationship between effectiveness knowledge and self-reported environmental behaviour. We are further interested in possible differences among different age groups, living places (city or countryside), and educational background.

A nudge is an instrument that originates from the libertarian paternalism. Thus, by intervening in people’s choice architecture, their behaviour is adjusted in a predictable way (Thaler & Sunstein, 2008). On cigarette packages, pictorial warning nudges have been proven to be effective in order to reduce cigarette consumption (e.g. Thrasher et al., 2007). Noar et al. (2016) showed that pictorial warning nudges on cigarette packaging increased the knowledge about the negative health consequences of smoking and evoked negative attitudes towards the cigarette product and the smoking-behaviour. Transferring these effects to the environmental context, a picture on plastic pollution could activate environmental awareness but also negative emotions. Negative emotions have been proven to be highly effective in order to foster responsible behaviours, such as consuming responsible-minded alcohol or behaving environmental-friendly (Agrawal & Duhachek, 2010; Becheur et al., 2007) The planned study implements pictorial warning nudges in order to reduce plastic pollution. More precisely, we focus on the consumption of plastic bottles. We examine the effect of a pictorial warning nudge by embedding a pictorial warning nudge about plastic pollution on a plastic bottle. Further, we want to investigate whether the nudging effect results from an activated awareness on plastic pollution or from an activated feeling of shame (or a combination of both mechanisms). Thus, the plastic-nudge will be compared to an aversive picture nudge that is unrelated to plastic pollution. Following the negative valence and the potentially activated awareness on plastic pollution the constructs feelings of shame and awereness about plastic pollution will be examined as potential mechanisms of the nudging effect.

Online experiment to test the effect of a pictorial warning nudge on the decision to select a plastic bag or textile bag