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The Use of Behavioral Science in International Law and Policymaking

Published online by Cambridge University Press:  04 February 2026

Anne van Aaken
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The United Nations (UN) as well as specialized UN agencies are turning to behavioral science. The UN clearly states that behavioral sciences should be included in its work to achieve its goals.1 In that, it follows the World Bank, which devoted its World Development Report 2015, “Mind, Society, and Behavior,” to behavioral insights in order to promote development.2 Let me stress from the outset that I deem this development necessary. It is highly promising that more realistic behavioral assumptions3 and insights underpin policies of international organizations (IOs), their member states, and international law.4 Still, when behavioral insights, especially nudges, are used, careful consideration of relevant scientific and normative limitations are needed to uphold legitimacy and accountability of those regulatory tools. Nudges and other behavioral interventions have been used nationally around the world5 and a lively discussion on their ethical and legal limitations has ensued on the national level.6

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Proceedings of the ASIL Annual Meeting , Volume 119 , 2025 , pp. 25 - 34
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Behavioral Sciences and International Law: A Roadmap and Some Stop Signs

The United Nations (UN) as well as specialized UN agencies are turning to behavioral science. The UN clearly states that behavioral sciences should be included in its work to achieve its goals.Footnote 1 In that, it follows the World Bank, which devoted its World Development Report 2015, “Mind, Society, and Behavior,” to behavioral insights in order to promote development.Footnote 2 Let me stress from the outset that I deem this development necessary. It is highly promising that more realistic behavioral assumptionsFootnote 3 and insights underpin policies of international organizations (IOs), their member states, and international law.Footnote 4 Still, when behavioral insights, especially nudges, are used, careful consideration of relevant scientific and normative limitations are needed to uphold legitimacy and accountability of those regulatory tools. Nudges and other behavioral interventions have been used nationally around the worldFootnote 5 and a lively discussion on their ethical and legal limitations has ensued on the national level.Footnote 6

A nudge is “an aspect of choice architecture that alters people’s behavior in a predictable way without forbidding any options or significantly changing their economic incentives.”Footnote 7 International nudges are regulatory tools used by international actors to influence the behavior of other actors, “either by nudging individuals who are vested with political power directly, or by nudging the public at large, which in turn influences policy-makers indirectly.”Footnote 8 Both give rise to questions of legitimacy of using behavioral sciences and matter for the accountability and responsibility of the (international) users of behavioral sciences. Although the constitutional and ethical implications of the use of nudges has been discussed on the national plane, almost no such discussion on human rights implications has been taking place in the international sphere.Footnote 9 This contribution aims at starting to fill that gap. It aims to show the many ways of using behavioral insights on the international plane (the roadmap). Secondly, it aims to raise awareness of potential scientific and legal limitations for behavioral interventions, especially nudges (the stop signs).

This contribution proceeds as follows. At the outset, it maps the relevant actors and applications since this allows for a differentiated view on scientific and normative concerns (I). It then draws attention to stop signs to be considered when using behavioral sciences in the international realm (II): first, a cursory discussion on validity and replication problems of experimental research underpinning much of the research background of the behavioral turn (II.A); and second, given certain human rights obligations of international organizations, normative considerations to be deliberated upon when using behavioral insights (II.B). The last part looks out for possible ways forward (III).

I. A Roadmap: Actors and Norms

Different actors are involved when using behavioral insights in international law. The first category of actors concerns those using behavioral insights for their policy goals. The actors can be divided between the national (or local) and the international level. At the national level, regulators on all level of government can use behavioral tools that are informed by international policies or norms, such as guidelines.Footnote 10 On the international level, it can be international negotiators and diplomats who use behavioral insights in negotiations,Footnote 11 be it with other states, be it with their home states.Footnote 12 It can also be IOs that use behavioral insights for the functioning of their own organization or to implement policies either directly or being used by the states as intermediaries. Indeed, the use of behavioral insights are often developed and implemented by so-called “behavioral units” of IOs. Prominent examples with such units are, inter alia, the Organization for Economic Co-operation and Development (OECD),Footnote 13 the European Union (EU),Footnote 14 the World Bank,Footnote 15 and the UNFootnote 16 and its agencies, such as the World Health Organization (WHO)Footnote 17 and the UN International Children’s Emergency Fund (UNICEF).Footnote 18 Already in 2017, the UN Environmental Programme (UNEP) issued a report on the use of behavioral insights for sustainable consumption with concrete examples from food, energy, water, transportation, and mobility, as well as wasteFootnote 19 and the OECD did so as well.Footnote 20

The second category of actors concerns those to whom the behavioral intervention is addressed. Those can be on the national (or local) level states respectively their governments. It can also be businessesFootnote 21 or consumers/citizens. On the international level, those can again be states, respectively their negotiators, e.g., when an international secretariat sets agendas or is involved in interstate negotiations. For the negotiation of environmental treaties, such as the Paris Agreement, behavioral insights have been discussedFootnote 22 and they have been used for the 12th Ministerial Conference at the WTO.Footnote 23

When contemplating the actors using behavioral insights and those targeted, the measures can take very different forms and can play out at different levels. On the international interstate level,Footnote 24 behavioral insights can be used in treaties. Here, it can play out in two ways. First, behavioral insights can be used in negotiation strategies (departing from rationalist negotiation theories). Or they can, secondly, use behavioral insights for the design of lawmaking, e.g., making use of default rules, based on insights concerning the status quo bias. Research demonstrates that states will opt-in significantly less frequently than opting-out; yet this may influence the willingness to commit.Footnote 25 Also compliance design can benefit from behavioral insights.Footnote 26 Furthermore, the use of soft law can be considered.Footnote 27 This has been explored for the Paris Agreement’s goal of keeping global temperature change below 2 degrees Celsius, it sets a psychologically powerful baseline against which future policy failures can be measured.Footnote 28 The WHO and its members have, e.g., used soft law based on behavioral insights successfully in the WHO Guidelines on packaging and labeling of tobacco productsFootnote 29 (e.g., when the World Trade Organization (WTO) Appellate Body upheld a Dispute Settlement Panel’s use of non-binding provisions of the guidelines as evidence of emerging tobacco control practices on plain packaging, thus turning soft law into hard law).Footnote 30 Plain packing laws are now found in many countries. Furthermore, IOs can gather best practices from states and distribute them as an information device—this would be a bottom-up approach to international guidance on the use of behavioral insights.

On the national level, many countries have behavioral insights units. Sometimes they are inspired by international norms,Footnote 31 but national regulatory practices may also in turn inspire international norms. They again can take different legal forms, such as formal laws, regulatory guidelines of national or sub-national agencies or just be regulatory practices—with different significance for their legitimacy and accountability toward the targeted actors.

II. Scientific and Normative Stop Signs for Behavioral Interventions

Clearly, the use of behavioral insights is on the rise in international law and policy. Those insights are sometimes used through the regulatory tool of nudging, but they are not confined thereto. Given this development, there is a need to reconsider their scientific (II.A) and normative limitations (II.B) with a special view to distinctive scientific and normative challenges when applying behavioral science to international law and policy.

A. Scientific Stop Signs

The origins of insights of behavioral sciences in departures from rational choice assumptions derive from experimental or survey research in controlled circumstances, employed to observe (individual or collective) actors’ cognition and real preferences and thus confer a high degree of internal validity to their findings.Footnote 32 Many experiments show systematic digressions from rationality assumptions on cognitive and motivational grounds, with significant implications for international law. Yet, there is some caution to be introduced and effectiveness of behavioral interventions matter for their legal and ethical assessment.

The external validity of experiments—the generalized applicability of implications beyond specific situations and outside of the laboratory—needs to be approached with caution. First, it is important to be mindful of the fact that people and societies are highly complex and learning systems. Most of the experiments are conducted in the Global North but their insights may be applied through behavioral policies of IOs all over the world. But unlike in natural sciences, a stone does not always fall everywhere on earth: gravity applies throughout the world, while behavior may differ depending on, e.g., different cultures as well as personalities.Footnote 33 A behavioral intervention working in the UK may not work in India.

What do we know about the effectiveness of nudges? First, alleviating the external validity problems, ever more research is conducted also in the field with Randomized Controlled Trials (RCTs).Footnote 34 Evidence is mixed. Sometimes, effectiveness of nudges could be shown.Footnote 35 But other studies indicated limited influences of nudging or even report backfiring effects with unintended consequences.Footnote 36 And of course, as has been lamented, ineffective behavioral studies are seldom reported.Footnote 37 One recent meta-study on the effects of behavioral interventions revealed that “only 62% of nudging treatments are statistically significant”Footnote 38—whether this is good or bad result lies in the eyes of the beholder. Another meta-study found that nudges are most effective in the food sector but less effective for other sectors, such as the environment, and that effectiveness varies across the type of nudge.Footnote 39

If behavioral interventions are proposed by IOs, they should be applicable everywhere in the world. And this should be less of a problem for universal cognitive biases, such as loss aversion, the availability bias, or anchoring. But if there are interventions built on phenomena that are clearly social in nature (e.g., social comparisons, as often used in the environmental sphere,Footnote 40 and other regarding behavior), cultural differences may matter. To my knowledge there is no cross-country study evaluating specifically similar behavioral interventions in different countries or regions of the world taking into account cultural context. Used as a proxy here, one survey finds different attitudes toward a variety of nudges in Europe and the United States.Footnote 41 It is plausible to expect that the effectiveness of behavioral interventions for people who reject certain behavioral interventions may be diminished and even counterproductive.

Not all types of nudges are created equal, and some have been proven to be more effective than others, e.g., default rules.Footnote 42 Furthermore, the same biases and heuristics may not be relevant for all application contexts. Environmental law and policy, be it on the national or international level, present special psychological and behavioral challenges since it is also psychologically distinctive as argued by Rowell and Bilz,Footnote 43 and may make environmental applications of behavioral science thornier than non-environmental goals. The human brain is not well adapted to tackle complex and diffuse future phenomena. People neglect in their decisions diffuse consequences harming others. They also tend to neglect long-term consequences, e.g., using plastic (present biasFootnote 44). Social comparisons, often used to nudge people into action for contributing to a public good, such as the environment, are less effective.Footnote 45 Some behavioral nudges may thus not work as well in the environmental sphere as in other applications.

Furthermore, internal validity of experiments has been questioned given the replication crisis in experimental research. It basically means that once an experiment is replicated, no statistically significant result is found. But does that necessarily imply a false positive result? It may be owed to the insights on external validity if subjects are different (e.g., from different cultures) in the replication studies rather than to the research design or outright cheating by researchers. Another plausible explanation is low statistical power in either the original study or single replication studies.Footnote 46 The awareness of the problem has already led to a worldwide endeavor to replicate and consolidate behavioral insights.Footnote 47 Since replication efforts are under way and pre-registration of experiments is happening more often,Footnote 48 this should help to confer reliability and precision of the results. Pre-registration would also diminish the positive results bias for publication that occurs when authors are more likely to submit, or editors are more likely to accept, positive results than negative or inconclusive results, even though the latter would also advance knowledge.

All those scientific stop signs need to be taken into account when using those insights in international law. Thus, a few desiderata can be formulated: (1) if international actors rely on behavioral insights, well documented empirical and settled knowledge should guide them; (2) the context and actors where those insights are used have to be well defined and understood; and (3) a possibility of exchange of good practices and knowledge about behavioral insights (including negative results) needs to be established—and to an extent this is beginning to take place in the innovation network of the UN in that in-house behavioral research is bundled in one unit.Footnote 49 Furthermore, experimental research has to be further complemented as far as possible with other types of research if fitting the research question, e.g., RCTs—as far as this is ethically permissible—and other social science methods, such as network analysis and agent-based modeling, both of which are research methods adapted to highly complex problems and can include behavioral assumptions. All this would confer confidence and trust in the insights gained by experimental studies specifically and behavioral policy tools generally.

B. Normative Stop Signs

The use of behavioral insights for regulation, especially “nudging” and its normative implications have been extensively and controversially discussed in legal, philosophical, and behavioral economic scholarship, but hitherto have been primarily confined to the national realm.Footnote 50 What has been less discussed is the use of behavioral science by IOs. This needs special attention due to two reasons. First, IOs have a much broader reach and thus more people will be affected by their regulatory policies and tools. Second, the democratic legitimacy of IOs is diminished in comparison with national governments in generalFootnote 51 and thus specifically also the legitimacy of the use of behavioral insights for regulation is not as strong as in the national realm. “The perception of legitimacy matters, because, in a democratic era, multilateral institutions will only thrive if they are viewed as legitimate by democratic publics.”Footnote 52 Although implementation of international policy mostly, but not exclusively, occurs at the domestic level, guidelines may thus exert a high influence on national regulators with less scrutiny by national regulators, potentially producing an accountability gap—if the IOs does not assess human rights compatibility and the state relies on the IOs to do so.

Thus, the human rights obligations of IOs themselves come to the fore. Can IOs have human rights obligations, and, if so, what are their sources?Footnote 53 Three sources need to be considered in our context. First, constituent instruments and mandates. For the UN, the UN Charter tasks the organization with promoting and universal respect for fundamental rights (Articles 1(3), 55(c)–56) and the prevailing view is that UN is bound by human rights under the UN Charter. The EU explicitly is bound by human rights (Article 6 TEU and the Charter of Fundamental Rights of the EU). For UNICEF, the respect for children’s rights evolves from its mandate.Footnote 54 Furthermore, IOs must not act contrary to its member states’ obligations, including human rights, to which member states remain bound despite having vested parts of their powers to IOs. A further source is international customary law (CIL). Many relevant civil rights, human dignity, privacy rights,Footnote 55 can arguably be viewed as having attained the status of CIL and the prevailing view considers IOs to be bound by CIL.Footnote 56 Unilateral acts of IOs as another source of human rights obligations. The World Bank, e.g., has, with the introduction of its inspection panel committed to the respect of human rights.Footnote 57 For international financial institutions, scholars state in the Tilburg principles (Principle 5) that: “As international legal persons, the World Bank and the IMF have international legal obligations to take full responsibility for human rights respect in situations where the institutions’ own projects, policies or programmes negatively impact or undermine the enjoyment of human rights.”Footnote 58

I will concentrate here on the application of behavioral science for ordinary citizens and consumers as targeted actors. Like their national counterparts, international “nudges” are not less immune to controversy, and as such they also raise normative questions about legitimacy and morality.Footnote 59

Not all behavioral interventions or nudges are created equal. Both, goals and means of a behavioral intervention need to be distinguished for a normative assessment.Footnote 60 What matters most for normative limits to nudging is first different goals pursued, that is, the distinction between behavioral interventions which target the wellbeing of the individual alone (so-called paternalistic nudges) and those which target behavior concerning externalities (in the economic sense), e.g., interventions to reduce (dirty) energy consumption. If the only intent of the measure is to reduce third party externalities or promote public welfare, paternalism is not involved. If third parties or public goods are to be protected, no special justification is necessary (together with the provision of public goods, making such allocative choices constitutes a core prerogative of states, being assisted by IOs). Some goals surely have both, the individual wellbeing as well externalities as a target—the delimitations can be fluid. Whereas the former has to be used with great caution,Footnote 61 the latter should in principle be permitted for furthering the common good.

Also, the means of behavioral interventions differ widely. Whereas some of them are transparent and thus unproblematic, others are hidden and sometimes manipulative, since they exploit people’s cognitive limitations and the subconscious rather than engage them as deliberative, autonomous, and rational agents (System II). They are often playing on subconscious or emotional levels of decision making (System I).Footnote 62 For example, a classical nudge is informing people about other people’s energy consumption to spur them to reduce theirs using social comparison. People tend to judge their position in relation to the positions of others and this is a powerful driver of behavior. Two problems arise here—the first is the play with powerful emotional drivers of people, the second concerns the framing of the information. Does this information, e.g., need to be truthful to achieve results?Footnote 63 And of course (including well intended) manipulations are possible, e.g., on local and time range of consumers to be counted in the benchmark of energy consumption. Who is able to control the information used in a nudge and how can the nudging actors be made accountable? The UN Refugee Agency (UNHCR) is experimenting with different communications targeted at a small group of influential people to induce empathy and change attitudes toward refugees as well as induce donations.Footnote 64 While there is no information on the concrete actions taken, as laudable as the goal is, the means may be manipulative and thus potentially not proportional. Whereas a similar problem arises on the national sphere, it is aggravated on the international one given that democratic legitimacy is missing, and accountability standards are far fewer than in the national realm where, ultimately, the use of behavioral sciences can be controlled by courts.

Drawing an analogy to liberal constitutions, one may argue that all regulation targeting individual freedom of decision making needs to be proportional.Footnote 65 This includes scrutinizing the goal of the behavioral intervention as previously mentioned, namely whether the goal is legitimately targeting externalities or whether it is paternalistic. When the suitability of the behavioral intervention is considered, all the scientific stop signs discussed above on internal and external validity are relevant, in particular the effectiveness of the interventions and the context. Non-effective interventions need to be deemed unsuitable and thus not proportional. It also needs to be considered if the intervention is necessary or if there are other, better suited means. This also implies a comparison of different types of behavioral interventions—including command and control. This is especially important for paternalistic interventions or interventions solely playing on System I. For example, a default which functions even without knowledge and consciousness, could be converted into a prompted decision. Finally, a sort of proportionality stricto sensu should be applied: is invisible manipulation (no matter what goal of intervention) really indispensable as a regulatory instrument of international governance?Footnote 66

III. Outlook

It is high time that behavioral sciences enter the international sphere. Without a thorough understanding of human behavior, policies to achieve the goals of IOs can fail. Although individuals and states still act strategically and pursue their goals, they do so often only with bounded rationality and often not entirely self-regarding. Thus, the behavioral approach can complement the rationalist approach but not discard it. Furthermore, individuals do not act in isolation and thus social cognition and cognitive and social psychology need to be added to understand the complexity of human behavior.

Given that behavioral approaches are gaining ground internationally and as a regulatory method of IOs, awareness about scientific and normative stop signs needs to be raised. The discussion that has taken place nationally also needs to take place internationally. Given that IOs are to some extent bound by human rights norms, those should be respected by behavioral insights units of IOs. The long-term consequences on autonomy and deliberation, next to the sustained effectiveness of nudging after the intervention ceases, need to be considered just as the implications for the institutions of liberal democracies as well as the values underpinning the international system. We need to move ahead with caution and be aware of the current limits of knowledge in behavioral sciences as well as of the normative implications of their use.

Ways forward are first of all awareness in all IOs, such as has been demonstrated by UNICEF, treading cautiously with behavioral interventions for children. Human rights compatibility also needs to be assured for adults, mutatis mutandis. This human rights compatibility matters for the legitimacy of using behavioral science just as for the for accountability and responsibility of its users. Principles such as human dignity, informed consent, stringent (data) security measures, rights-by-design, human agency enhancing policies should be incorporated, even more so if behavioral interventions are scaled with AI. There must be a detailed risk assessment for privacy, autonomy, mental integrity of behavioral targets and cultural sensitivity, adapted to respective intervention, e.g. if it concerns social norms, such as in some World Bank projects on female participation in the work force in Jordan.Footnote 67 One way forward would be to develop formalized ethics review proceduresFootnote 68 (as in academia) with the participation of international lawyers.

Footnotes

This panel was convened at 3:30 p.m. on Thursday, April 17, 2025, by Anne van Aaken, University of Hamburg, Germany and Moshe Hirsch, Hebrew University, Israel, who moderated the panel and introduced the panelists: Anne van Aaken, Professor for Law and Economics, Legal Theory, Public International Law and European Law, Alexander von Humboldt Professor 2018–2023, University of Hamburg, Director, Institute of Law and Economics, Distinguished Fellow, Hebrew University, Jerusalem; Benn McGrady, Unit Head, Public Health Law and Policies, Health Promotion DepartmentWorld Health Organization; Renos Vakis and Michelle Dugas, The Mind, Behavior, and Development Unit of the World Bank. Since the latter were unable to contribute to the Proceedings, Anne van Aaken extended her talk to include some examples given by the IO representatives, referring to their slides in the footnotes.

*

Evelyn Aswad is the Herman G. Kaiser Chair in International Law at the University of Oklahoma College of Law where she also serves as the Director of the International Business Law Online Graduate Degree Program and the Director of the Center for International Business & Human Rights. She thanks her fellow panelists for an illuminating discussion on the various aspects of analyzing Internet shutdowns.

References

1 António Guterres, UN Secretary-General’s Guidance on Behavioural Science, 4 (2021), at https://www.un.org/en/content/behaviouralscience.

2 World Bank, World Development Report (2015), at https://www.worldbank.org/content/dam/Worldbank/Publications/WDR/WDR%202015/WDR-2015-Full-Report.pdf.

3 See for a juxtaposition of the classical rationalist assumptions of behavior and behavioral science the slides of Renos Vakis and Michelle Dugas, slide 4: “From deliberative (carefully avoids systematic errors), selfish (behaviors from others are not relevant), objective (the world is perceived as it is) to automatic (use and rely on heuristics), social (do what others do or expect from us), preconceived (use beliefs and preconceived ideas). From this follow also other policy instruments”; slide 5: “From standard policy tools (information, incentives and prices, laws and regulations) to behavioral policy tools (environmental cues, social networks, mindsets and beliefs).”

4 Behavioral sciences, especially behavioral economics, has been applied to international law since almost ten years with rapidly growing literature, see instead of many: Harlan Grant Cohen & Timothy Meyer, International Law as Behavior (2021); Anne van Aaken, Behavioral International Law and Economics, 55 Harv. Int’l L.J. 421 (2014); Anne van Aaken, Behavioral Aspects of the International Law of Global Public Goods and Common Pool Resources, 112 AJIL 67 (2018); Tomer Broude, Behavioral International Law, 163 U. Penn. L. Rev. 1099 (2015).

5 Cass R. Sunstein et al., A Worldwide Consensus on Nudging? Not Quite, But Almost, 12 Reg. & Gov. 3 (2018).

6 The literature is legion. Instead of many, see: Mark D. White, The Manipulation of Choice. Ethics and Libertarian Paternalism (2013); Jeffrey J. Rachlinski, The Uncertain Psychological Case for Paternalism, 97 Nw. U. L. Rev. 1165 (2003); Pelle Guldborg Hansen & Andreas Maaløe Jespersen, Nudge and the Manipulation of Choice: A Framework for the Responsible Use of the Nudge Approach to Behaviour Change in Public Policy, 4 Eur. J. Risk Reg. 3 (2013); Christopher McCrudden & Jeff A. King, The Dark Side of Nudging: The Ethics, Political Economy, and Law of Libertarian Paternalism, in Choice Architecture in Democracies – Exploring the Legitimacy of Nudging 67 (Alexandra Kemmerer et al. eds., 2016); Anne van Aaken, Judge the Nudge: In Search of the Legal Limits of Paternalistic Nudging in the EU, in Nudge and the Law. A European Perspective 83 (Alberto Alemanno & Anne Lise Sibony eds., 2015); Anne van Aaken, Constitutional Limits to Nudging: A Proportionality Assessment, in Choice Architecture in Democracies: Exploring the Legitimacy of Nudging 199 (Alexandra Kemmerer et al. eds., 2016).

7 Richard H. Thaler & Cass R. Sunstein, Nudge: Improving Decisions About Health, Wealth, and Happiness 6 (2008). For a critique of the notion, see Daniel M. Hausman & Brynn Welch, To Nudge or Not to Nudge, 18 J. Pol. Phil. 123 (2010).

8 Doron Teichman & Eyal Zamir, Normative Aspects of Nudging in the International Sphere, 115 AJIL Unbound 263 (2021).

9 One notable exception is Karen Tindall et al., Ethical Considerations When Applying Behavioural Science in Projects Focused on Children (UNICEF Office of Research – Innocenti Discussion Paper DP 2021-03, Oct. 2021), at https://www.unicef.org/innocenti/media/5186/file/UNICEF-Ethical-Considerations-Behavioural-Science-Children-2021.pdf. The World Bank seems to plan to have an ethics review.

10 Examples such as improving labor market outcomes by removing behavioral bottlenecks for female workforce participation in Jordan and misinformation inoculation is given by Renos Vakis and Michelle Dugas.

11 Russell B. Korobkin & Chris Guthrie, Heuristics and Biases at the Bargaining Table, 87 Marq. L. Rev. 795 (2004); Andrea Caputo, A Literature Review of Cognitive Biases in Negotiation Processes, 24 Int’l J. Confl. Mgmt. 374 (2013).

12 For a difference of views between negotiators and their home state administration, see for trade law: Bernard Hoekman & Robert Wolfe, The Geneva Effect: Where Officials Sit Influences Where They Stand on WTO Priorities (Working Paper, EUI RSC, 2022/37, Global Governance Programme-471, 2022), at http://hdl.handle.net/1814/74557.

13 OECD, Behavioural Insights, at https://www.oecd.org/gov/regulatory-policy/behavioural-insights.htm (accessed June 28, 2025).

14 European Commission, Competence Centre on Behavioural Insights, at https://knowledge4policy.ec.europa.eu/behavioural-insights_en (accessed June 28, 2025).

15 World Bank, The Mind, Behavior, and Development Unit (eMBeD), at https://www.worldbank.org/en/programs/embed (accessed June 28, 2025).

16 Guterres, supra note 1.

17 WHO, World Health Organization’s Technical Advisory Group on Behavioural Insights and Sciences for Health, at https://www.who.int/our-work/science-division/behavioural-insights (accessed June 28, 2025). As Benn McBrady has shown in his talk, the WHO has been using behavioral insights since 2020 and has had a behavioral insights unit since 2022. The WHA 76.7 Resolution and regional resolutions were adopted in 2023 to make behavioral science part of a healthier population campaign, see WHO, Behavioral Sciences Global Agenda, at https://www.who.int/initiatives/behavioural-sciences/behavioural-sciences-global-agenda (accessed June 28, 2025).

18 UNICEF, Bringing Behavioural Insights to Scale in the United Nations (Dec. 10, 2018), at https://www.unicef.org/innovation/stories/behavioural-insights-UN.

19 UNEP, Consuming Differently, Consuming Sustainably: Behavioral Insights for Policymaking (2017), at https://sdgs.un.org/sites/default/files/publications/2404Behavioral%20Insights.pdf.

20 OECD, Tackling Environmental Problems with the Help of Behavioural Insights (2017), at https://www.oecd.org/environment/tackling-environmental-problems-with-the-help-of-behavioural-insights-9789264273887-en.htm.

21 Mark Armstrong & Steffen Huck, Behavioral Economics as Applied to Firms: A Primer, 6 Competition Pol. Int’l 3 (2010); OECD, Behavioural Insights and Organisations. Fostering Safety Culture (2020), at https://www.oecd.org/gov/regulatory-policy/behavioural-insights-and-organisations-e6ef217d-en.htm.

22 Anne van Aaken & Jan-Philip Elm, Framing in and Through International Law, in International Law’s Invisible Frames – Social Cognition and Knowledge Production in International Legal Processes 35 (Andrea Bianchi & Moshe Hirsch eds., 2022); Scott Barrett & Astrid Dannenberg, Sensitivity of Collective Action to Uncertainty About Climate Tipping Points, 4 Nat’l Clim. Change 36 (2014); Andrew Schein & Zac Baynham-Herd, What if a Behavioural Scientist Redesigned Climate Negotiations?, Behavioral Insights Team Blog (July 28, 2021), at https://www.bi.team/blogs/what-if-a-behavioural-scientist-redesigned-climate-negotiations.

23 Anne van Aaken, Making Trade Agreements Contribute to Sustainability: The Potential of Behavioural Science, in The Sustainability Revolution in International Trade Agreements 23 (Geraldo Vigidal & Kathleen Claussen eds., 2024).

24 On the use of behavioral science and law, see Eyal Zamir & Doron Teichman, Behavioral Law and Economics (2018). How behavioral insights can and are used between countries, see Doron Teichman & Eyal Zamir, Nudge Goes International, 30 Eur. J. Int’l L. 1263 (2020).

25 Jean Galbraith, Treaty Options: Towards a Behavioral Understanding of Treaty Design, 53 Va. J. Int’l L. 309 (2013).

26 Anne van Aaken & Betül Simsek, Rewarding in International Law, 115 AJIL 195 (2021).

27 Tomer Broude & Yahli Shereshevsky, Explaining the Practical Purchase of Soft Law: Competing and Complementary Behavioral Hypotheses, in International Law as Behavior (Harlan Grant Cohen & Timothy Meyer eds., 2021).

28 Arden Rowell & Josephine van Zeben, A New Status Quo? The Psychological Impact of the Paris Agreement on Climate Change, 7 Eur. J. Risk Reg. 49 (2016).

29 WHO, Guidelines for Implementation of Article 11 of the WHO Framework Convention on Tobacco Control (2011), at https://fctc.who.int/resources/publications/m/item/packaging-and-labelling-of-tobacco-products. Those behaviorally informed guidelines were also the example used by Benn McGrady to showcase the interaction between behavioral science and international law in his talk.

30 WTO, Australia – Certain Measures Concerning Trademarks, Geographical Indications and Other Plain Packaging Requirements Applicable to Tobacco Products and Packaging (June 9, 2020), at https://www.wto.org/english/tratop_e/dispu_e/435_441abr_e.pdf.

31 Francesco Bogliacino et al., Nudging in the World of International Policymaking, in The Behavioral Economics Guide (Alain Samson ed., 2014).

32 Internal validity describes a trustworthy cause-and-effect relationship between a treatment and an outcome. See also the ASIL presentation of the World Bank Panelists, slides 4 and 5, contrasting rational choice assumptions with behavioral insights on human decision making.

33 Joseph Henrich, The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous (2020).

34 A randomized controlled trial is an experimental form of impact evaluation in which the population receiving the program or policy intervention is chosen at random from the eligible population, and a control group is also chosen at random from the same eligible population. This has been used, for example, by Nobel Prize winners for development economics: Abhijit Banerjee & Esther Duflo, Poor Economics: A Radical Rethinking of the Way to Fight Global Poverty (2011).

35 The latest meta-study compares RCT in the United States from two different nudging units: Stefano DellaVigna & Elizabeth Linos, RCTs to Scale: Comprehensive Evidence From Two Nudge Units, 90 Econometrica 81 (2022).

36 Giovanna d’Adda et al., Push, Don’t Nudge: Behavioral Spillovers and Policy Instruments, 154 Econ. Letters 92 (2017).

37 Nudges That Don’t Nudge, 4 Nat. Hum. Beh. 121 (2020). For one example in the environmental field, see Sumit Agarwal et al., Water Conservation Through Plumbing and Nudging, 6 Nat. Hum. Beh. 858 (2022).

38 Dennis Hummel & Alexander Maedche, How Effective Is Nudging? A Quantitative Review on the Effect Sizes and Limits of Empirical Nudging Studies, 80 J. Beh. & Exper. Econ. 47(2019). They find that most studies are conducted in the health context (thirty-eight), followed by environment (nineteen). The latter use social referencing most often.

39 Stephanie Mertens et al., The Effectiveness of Nudging: A Meta-Analysis of Choice Architecture Interventions Across Behavioral Domains, 119 Proc. Nat’l Acad. Sci. e2107346118, 7 (2022) (“reveals substantial variations in the effectiveness of choice architecture as a behavior change tool”). They find that across behavioral domains, decision structure interventions that modify decision environments to address decisionmakers’ limited capacity to evaluate and compare choice options are consistently more effective in changing behavior than decision information interventions that address decisionmakers’ limited access to decision-relevant information or decision assistance interventions that address decisionmakers’ limited attention and self-control.

40 Hummel & Maedche, supra note 38.

41 Lucia A. Reisch & Cass R. Sunstein, Do Europeans Like Nudges?, 11 Judgment & Decision Making 310 (2016).

42 Hummel & Maedche, supra note 38.

43 Arden Rowell & Kenworthey Bilz, The Psychology of Environmental Law 29 (2021).

44 The present bias refers to the tendency of people to give stronger weight to payoffs that are closer to the present time when considering trade-offs between two future moments. Ted O’Donoghue & Matthew Rabin, Doing It Now or Later, 89 Am. Econ. Rev. 103 (1999).

45 Hummel & Maedche, supra note 38.

46 Scott E. Maxwell et al., Is Psychology Suffering from a Replication Crisis? What Does “Failure To Replicate” Really Mean?, 70 Am. Psych. 487 (2015); John Bohannon, About 40% of Economics Experiments Fail Replication Survey: Compared with Psychology, The Replication Rate “Is Rather Good,” Researchers Say, Sci. (Mar. 3, 2016), at https://www.science.org/content/article/about-40-economics-experiments-fail-replication-survey.

47 The Replication Network, Furthering the Practice of Replication in Economics, at https://replicationnetwork.com/tag/psychology.

48 Patrick E. Shrout & Joseph L. Rodgers, Psychology, Science, and Knowledge Construction: Broadening Perspectives from the Replication Crisis, 69 Ann. Rev. Psych. 487 (2018).

49 UN Innovation Network, at https://www.uninnovation.network (accessed June 28, 2025). UN Innovation Network has set up the UN Behavioural Science Group, which comprises of more than 800 members from more than forty UN entities and sixty countries. The group promotes awareness and supports behavioral science work at the UN; provides learning opportunities about behavioral sciences and methods and collaborates with academics in the behavioral sciences and organizations specializing in designing and implementing behaviorally informed projects.

50 Note 6 supra.

51 Jonas Tallberg & Michael Zürn, The Legitimacy and Legitimation of International Organizations: Introduction and Framework, 14 Rev. Int’l Org. 581 (2019).

52 Allen Buchanan & Robert O. Keohane, The Legitimacy of Global Governance Institutions, 20 Eth. & Int’l Aff. 405, 407 (2006).

53 See for a detailed discussion: Martin Faix, Are International Organisations Bound by International Human Rights Obligations?, 5 Czech Y.B. Int’l L. 267 (2014); Jan Wouters et al., Accountability for Human Rights Violations by International Organisations (2010).

54 Tindall et al., supra note 9.

55 Article 12 of the Universal Declaration of Human Rights (UDHR), Article 17 of the International Covenant on Civil and Political Rights (ICCPR). While treaty protections for privacy are strong, the customary status of the right to privacy remains less clearly established than that of freedom from torture or slavery though, see Andrew Clapham, Human Rights: A Very Short Introduction 108 et seq. (2d ed. 2015).

56 Niels Blokker, International Organizations and Customary International Law: Is the International Law Commission Taking International Organizations Seriously?, 14 Int’l Org. L. Rev. 1 (2017).

57 Daniel D. Bradlow & Sabine Schlemmer-Schulte, The World Bank´s New Inspection Panel: A Constructive Step in the Transformation of the International Legal Order, 54 Heidelberg J. Int’l L. (ZaöRV) 392 (1994).

58 Willem van Genugten et al., Tilburg Guiding Principles on World Bank, IMF and Human Rights (2003); Daniel D. Bradlow, The World Bank, the IMF, and Human Rights, 6 J. Transnat’l L. & Contemp. Prob. 47 (1996).

59 See note 6 supra.

60 Bogliacino et al., supra note 31.

61 See note 6 supra.

62 For those categories that are now well established in psychology, see the Nobel Lecture Daniel Kahneman, Maps of Bounded Rationality: A Perspective on Intuitive Judgment and Choice. Prize Lecture, December 8, 2002, at https://www.nobelprize.org/uploads/2018/06/kahnemann-lecture.pdf.

63 On the human rights implications of lying, see Marko Milanovic, State Lies as Violations of Human Rights, Hum. Rts. Q. (forthcoming).

64 UNHCR Innovation Service, Essays from the Edge of Humanitarian Intervention 51 (2018), at https://www.unhcr.org/innovation/wp-content/uploads/2018/01/InnovationYearInReview2017_web.pdf.

65 Jan Sieckmann, Proportionality as a Universal Human Rights Principle, in Proportionality in Law: An Analytical Perspective (David Duarte & Jorge Silva Sampaio eds., 2018).

66 See for details on proportionality, van Aaken, supra note 6.

67 See presentations of Renos Vakis and Michelle Dugas of the World Bank at the panel.

68 See for this suggestion also Aiswarya Sunil et al., Advancing Sustainable Consumption: SDG 12, Behavioural Science, and the Work of the United Nations, in The Elgar Companion to Consumer Behaviour and the Sustainable Development Goals (Lucia A. Reisch & Cass R. Sunstein eds., 2025).