Can Nudge Plus help us encourage sustainable pro-social behaviour change?

By Sanchayan Banerjee, PhD student at the London School of Economics and Political Science * |

Nudges are low-cost, high-impact behavioural strategies that encourage people to make welfare-improving individual decisions, but can we promote persistent yet autonomous pro-social behaviour with them? Sanchayan explains the theory of nudge-plus, and why it may have the answer.

The introduction of Nudge Theory by Thaler and Sunstein (2009)[i]  has revolutionised the way we encourage positive behaviour in public policy. Humans tend to be quite myopic and as such fail to account for the temporality of their actions. This can lead to, amongst other things, present bias, our tendency to settle for a smaller reward if we get it earlier, as well as a whole load of other biases. Nudges aim to exploit these biases and use this understanding to present choices to individuals in such a way as to encourage positive behaviour. However, ensuring a long-lasting change behaviour change can be difficult with reflexive nudges alone.

Nudges only go as far as changes to the choice architecture will allow and can limit autonomy and human agency

Nudges can fail to achieve long lasting, persistent behavioural changes because they work by only manipulating the choice architecture and, as such, leave citizens out of the behavioural change mechanism. Human agency and autonomy can also be reasonably compromised as well.  Consider a simple commitment contract to tackle the problem of student attendance at lectures. Individuals signing these contracts lock themselves in to a certain level of attendance throughout the year, thereby aiming to overcome their present bias. Someone who has enrolled on the course may sign the contract and start adhering to the attendance agreement they signed up to, with the intention of aligning to the long-term goal of high attendance, however, they may occasionally regret this action as they’ve lost their autonomy, this could lead to ‘cheat days’ to reward themselves for their hard work, reasserting their autonomy, but undoing the good work of the commitment device and potentially harming their degree.

So, while the attendance pledge overcomes a student’s preferential inconsistencies by locking their present self into an action plan that aligns them with their long-term goal, the contract fails to engage them in the process of the behaviour change. This has been recently acknowledged by Sunstein (2017)[ii] as he accounts for various reasons for which nudges might fail[iii].

Embedding a reflective element in a nudge can help sustain behavioural changes

The idea of nudge-plus, put forward by John[iv] and Stoker[v] aims to rectify this issue by embedding a reflective strategy in the nudge. This theory is rooted in a hybrid functioning of our  cognitive dual processes: the fast and slow brain. Take for instance, the commitment pledge discussed earlier. According to dual-self theory, humans can be thought to comprise of a short-run doer self, who is myopic; and a long-run planner self, that is rational. Most often, these short-and long-run selves are inconsistent in their preferences, leading to biased decision making. Nudge plus facilitates these two selves in the behavioural change process by engaging that rational self through reflection alongside the nudges that target the myopic self.

To apply this idea to the commitment device, we propose a dual-self pledge[vi]. The student would now be given two contracts; one where the student signs up for a present-self pledge with a short-term attendance goal in mind (say termly); and a future-self pledge with a long-run attendance target (say yearly). The student is also given the option to review the present-self pledge after the end of the term when they can revisit their current goals and update them in line with their long-run goals.  This should help the student retain their autonomy and agency by updating their goals. Furthermore, after every period, as the student updates their goals, they undergo a transformation of their perspectives, feeding back into the process of behaviour change that they now own.

Where do we stand currently with nudge plus?

Banerjee, John and colleagues[1] are systematically testing multiple variants of nudge pluses. For example, looking at how they may promote the uptake of sustainable diets. Sustainable diets, as defined by them, are environmentally sustainable in nature such that the carbon footprint of the diets promoted is below their median level as measured by the (lifecycle) carbon emissions embedded in their menu available to the respondents. This experimental survey, currently undergoing pilot testing, will be administered through Prolific, a leading digital crowdsourcing platform, to a sample of 3,000 citizens in the United Kingdom, and will help us in holistically understanding the effectiveness of these instruments against one another.

Can we use nudge plus to encourage sustainable pro-social behaviour?

This study will be influential in understanding how reflection in nudge pluses help individuals to adopt a sustainable behaviour.  We’re also interested in assessing whether a further theoretical advantage of embedding reflection in nudges is that it can lead to rippling effects across several behavioural domains, often known to scholars as a behavioural spill over. For instance, if a student successfully adheres to their attendance plan for one course, will it improve their overall attendance? Will they adopt other pro-social behaviours? For instance, will they follow through on other plans they might otherwise have cancelled, such as to volunteer?

This is exciting work and we look forward to communicating our results when we have them. We hope that nudge-plus will help us understand how we can encourage pro-social behaviour, including sustainable living and help us to put back a bit of humanity into our economic system.


Click here to join our mailing list.
Follow us on Twitter: @KCLWhatWorks


[1] Susana Mourato, Professor of Environmental Economics and Dr. Matteo Galizzi, Assistant Professor of Behavioural Science at the London School of Economics and Political Science.

[i] Thaler, R., & Sunstein, C. (2009). Nudge. Penguin Books

[ii] Sunstein, C. (2017). Nudges that fail. Behavioural Public Policy, 1(1), 4-25.

[iii] To take a real-world example, a pledge has recently been used as a nudge by What Works to overcome present bias in the PACT trial . A trial to encourage parents to talk about university with their children. As described in their recent summary report, this trial had a null result, and one possible reason What Works give is that parents felt they didn’t feel properly engaged with the process.

[iv] John, P. (2018). How far to nudge? Assessing behavioural public policy. Edward Elgar

[v] John, P., & Stoker, G. (2019). Rethinking the Role of Experts and Expertise in Behavioural Public Policy. Policy & Politics, 47(2), 209-226.×15526371698257

[vi] Banerjee S and John P (2020) Nudge plus: incorporating reflection into behavioural public policy. Grantham Research Institute on Climate Change and the Environment Working Paper 332. London: London School of Economics and Political Science

Acknowledgment: All views expressed in this article belong to the author. The author would like to express his sincere gratitude to Prof. Peter John for his insightful comments and feedback on this article, and to Ms. Vanessa Todman for extending this opportunity to write for this blog and for her excellent editorial inputs.

*Sanchayan is a third year PhD student at the London School of Economics and Political Science. His research lies at the intersection of environmental, behavioural and experimental economics in extending the theory of nudge-plus and testing it. Sanchayan is an Associate Fellow of the Higher Education Academy (AFHEA) and is a teaching assistant at LSE.

Be the first to comment

Leave a Reply

Your email address will not be published.