Developing an Interdisciplinary Vocabulary of Complexity and Plasticity Using a Case-Study of Plant-Based Diet Adoption

Abstract

Complexity and plasticity are increasingly popular concepts used to make sense of dynamics in the physical and social worlds. These concepts are relevant to a broad spectrum of disciplines, even disciplines where they are not explicitly used. In this article, we further conceptual understanding of plasticity and complexity from different disciplinary perspectives. We also consider how these concepts relate to one another. To do so, we first review how plasticity and complexity manifest at different scales and across our four disciplines: neuroscience, physics, cultural theory and public health. Next, we activate our interdisciplinary perspectives to understand how complexity and plasticity help us understand plant-based diet adoption, a case study that resonates with our different disciplines. We explore plasticity at different scales (neural, individual, network, societal) and how they may cascade. We then synthesise these perspectives to understand how plasticity and complexity may help us understand social change. Most of our disciplinary and interdisciplinary interrogations find that plasticity is an important property of complex systems. Ultimately, this article further contributes to developing interdisciplinary vocabularies of both plasticity and complexity and aims to offer conceptual tools for understanding complex social-physical phenomena.

Introduction

Across many disciplines, the concepts of complexity and plasticity resonate and help researchers understand biological and social phenomena. These distinct concepts are related: being plastic refers to a system, component or organism's ability to change its structure, state or behaviour in response to internal or external influence; being complex refers to being composed of heterogeneous interacting parts, with: (a) nonlinear interactions, where small changes can produce disproportionately large or unexpected effects (b) feedback loops, where the output of the system is reintroduced as an input, and (c) emergent patterns, or structures or behaviours that arise at the system level from many local interactions, and cannot be reduced to the properties of individual parts (Ladyman, Lambert, and Wiesner 2013). We often think of systems, like ecosystems or society overall, as complex. In short, plasticity describes the capacity of things or organisms to change, and complexity describes the process that gives rise to broader change (Adami 2002).

Even though researchers across different disciplines have considered how plasticity and complexity relate to one another (Aston 2017; Aston 2019; Ghalambor, Martin, and Arthur Woods 2014; Stevens, Wund, and Mathis 2023), using them alongside each other in research is uncommon. How might these concepts be complementary, and how might they overlap? Is there complexity in plasticity, where the process of plastic change is itself complex and multi-layered? Or is there plasticity of a complex system, where plasticity can be an emergent property due to the interactions within the complex system? Or plasticity in a complex system, where adaptive changes are nested within a larger complex network? An exploration of these questions has not yet been undertaken.

Our process started at the workshop, organised as part of the ‘Plasticity - here, there and everywhere’ project, held at the Institute for Advanced Studies in Amsterdam in September 2023. One proposition was made by Peter Sloot in the Plasticity workshop: ‘All complex systems show plasticity’ (Center for Unusual Collaborations 2023). As part of a round table group, the authors began by discussing the relevance of complex systems approaches for understanding plasticity. This article formalises and expands this early conversation.

We organised our investigation and this article around the Centre for Unusual Collaboration's stages of interdisciplinary research: (a) disciplinary grounding, in which we familiarise ourselves with our different fields’ approaches to plasticity and complexity; (b) perspective taking, where we address a research problem from our own disciplinary lenses while remaining in conversation with each other's disciplines; (c) finding common ground, in which we find moments of overlap among our different perspectives; and (d) integrating perspectives, where we synthesise our different perspectives toward a greater understanding (Centre for Unusual Collaborations 2024; Repko and Szostak 2021). For steps 2–4, we oriented our findings around a case study that is both deeply socially relevant, and applicable to each of our disciplines: how more widespread adoption of plant-based diets might occur. We chose to focus on a case study with particular relevance for public health, because this is a discipline in which ‘plasticity’ has received almost no scholarly attention, while ‘complexity’ is increasingly popular and widely applied (Mudd et al. 2024). Once we defined how our individual fields approach this topic in relation to plasticity and complexity (stage 2: perspective taking), we reflected on how different disciplines might be relevant for each other, and public health specifically (stage 3: finding common ground). Finally, we offer insights into how and why complex systems and plasticity may be relevant and related concepts, and how they might be applied across disciplines. In this last stage, this integration enabled us to reach a transdisciplinary understanding of the concepts of complexity and plasticity, and the relationships between them. Together, these four stages form a cycle that enables truly interdisciplinary research, that both benefits from the methodological rigor of our individual domains and produces knowledge greater than the sum of its parts.

Disciplinary Grounding

Grounding in Neuroscience: Plasticity of the Complex Brain

The use of plasticity within the subfields of neuroscience is diverse. Some neuroscientists use the term ‘developmental plasticity’, which refers to specific periods during early life when the circuitry is especially prone to rewiring, which can be through learning or stressful life experience (Galván 2010; Pollak 2005). Neurobiologists and physicists commonly use plasticity at the level of neuronal connectivity, as in synaptic or dendritic plasticity, which refers to structural changes that lead to a shift in presence, strength or perceptiveness to connectivity between neurons primarily due to neuronal activity (Cramer et al. 2011). These, and many additional plastic events in the brain take place in complex systems ranging in size from synapses to cells and neural networks (von Bernhardi, Bernhardi, and Eugenín 2017). These components are not disconnected, but can influence each other. Thus, it is not surprising that the methodology and terminology commonly used in complex systems has been adapted in studying these concepts in the brain.

The relationship between complexity and plasticity can be considered from two opposite perspectives. On the one hand, plasticity is a complex process. For instance, the decision for synaptic plasticity to take place is an interplay between the molecular components of the synapse, the frequency of activation of the connected cells and the behavioural consequences of this activation (e.g., within a social circle). However, neuroscientists typically emphasise the second perspective, plasticity within complex system dynamics. In a sense, complexity can provide the necessary tools for plasticity to take place. Synaptic plasticity takes place by changing the set of proteins, and hence the physiology, of a synapse, which is a complex, partially self-sustaining system (Pozo and Goda 2010). The complexity of the synapse allows it to assume multiple shapes and forms that become stable in different states. Similar to thermodynamic systems, the synapse becomes permanently resident in a new state, at least until a new external input, which results in synaptic plasticity. Hebb was the first to propose that activation of multiple cells together may lead to their connectivity in a higher order system, the neuronal ensemble, units of brain networks (Yuste, Cossart, and Yaksi 2024). In a sense, synaptic plasticity may be the mechanism of this Hebbian rule that coactivation of neurons connected with weak synapses may lead to the formation of neuronal ensembles, which themselves are prone to experience dependent plasticity (Alejandre-García et al. 2022; Pozo and Goda 2010).

The complexity is not limited to the molecules involved in these processes, but also to different modes of responses that can be given by a neuron. For instance, learning associated changes in a synapse can lead to a phenomenon called synaptic scaling, which describes changes in a major number of synapses on a single neuron (Pozo and Goda 2010). Neurons have more tricks up their sleeves, as they can modulate their responsiveness to input through dendritic plasticity or form a cellular memory of critical events, such as early life stress, through epigenetic plasticity. Neuronal morphology and chromatin are complex systems that only make sense when the parts work together, and the limitless possibilities can be exploited to assume new states that can grant plastic deformation, a term we borrow here from material science, of the synapse/cell/chromatin (Molnar and Labouesse 2021).

In fact, we know that the plasticity of complex systems at different scales can affect each other. As humans, our actions alter our surroundings which eventually affect the plasticity of our own brain. The invention of social media has arguably been one of the most drastic changes in our communication culture. Our brains learn how to use online communication, which is not something we are evolutionarily selected for. This inescapably induces neural plasticity – as any other learning process would – but not in a way that we would encounter in environments we evolved for. This sort of plasticity, also referred to as a form of metaplasticity by Malafouris, extends beyond the molecular processes (Malafouris 2015). Yet, neither of these examples does justice to the complexity of the system and its unpredictable nature. Even though the activity-mediated synaptic stabilisation resonates with deterministic events, the stochastic molecular changes in the synaptic cleft leaves room for errors as well as different outcomes to similar stimuli. This perhaps allows some sort of cognitive plasticity that may lead to individuation of identity through subtle, unpredictable differences in reorganisation of neural networks (Allen and Williams 2011; Destexhe and Marder 2004; Ribrault, Sekimoto, and Triller 2011). Of note, the concept of individual's identity goes beyond the concept of not only cognition, but likely also the brain's neurobiological processes (Gallagher 2016).

Grounding in Physics: Complex Systems and Their Plastic Potential

The complex system is one of the central themes in physics. Starting from the Big Bang, the complexity of the Earth has only increased, as more and more complex structures formed over time, from elementary particles, to cells, to even complex societies. This suggests the so-called arrow of time (Lineweaver, Davies, and Ruse 2013). From a Big History perspective, with the increasing rate of energy flowing through matter per unit time and mass since the Big Bang (Chaisson 2013), complex structures emerge ‘within certain favourable boundaries’ (Spier 2011) and ‘between order and chaos’ (Crutchfield 2012). In other words, there is a complexity/emergence cascade from elementary particles, to living matter, animals, culture, and society, over time and over spatial scales.

Traditionally, in physics, the term plasticity is defined in continuum mechanics, describing a solid material as the ability to deform irreversibly in response to applied forces (Bruhns 2018), and more precisely, before its fracture. This contrasts with elasticity, in which the deformation is reversible; once the external force is removed, it returns to its own shape. However, this definition is only confined to the mechanical, deforming malleability of materials.

On the other hand, the term plasticity has been used widely and considerably in neuroscience. Physicists directly adopted such a definition to apply plasticity beyond the mechanical malleability of materials but to the capacity of forming neural connections. For example, physicists built mathematical and dynamical models on synaptic plasticity (e.g., see Abarbanel, Huerta, and Rabinovich 2002, with others built by scientists beyond physicists in Morrison, Diesmann, and Gerstner 2008). Based on the model(s) of synaptic plasticity and modelling neurons and synapses as electric circuits (as network architecture), they studied the dynamics and stability of different states of neural systems using theories of nonlinear dynamics (Maistrenko et al. 2007; Rabinovich et al. 2006). As seen from above, the term plasticity has been separately employed in two different ways: (a) continuum mechanics as deforming malleability, and (b) as the capacity of forming neural connections of a neuronal system (a complex system). It may be useful to combine these two definitions and extend the term ‘plasticity’ to general complex systems.

To generalise the notion of plasticity to complex systems beyond neuroscience, we consider complex systems that can be described by networks (Thurner, Klimek, and Hanel 2018). A network is defined by its parts, which can be information, particles and/or humans, among others, and the interaction rules between them. Then, combining the two definitions above, one may define the plasticity of a complex system as, in the presence of external influence and the system itself initially is in a ‘quasi-statistically equilibrium state’, or the ability to rewire the interactions between the parts and/or to modify the parts irreversibly/permanently (before its failure). If the system returns to its initial state by itself when the external force is removed, then it is only an elastic deformation.

As mentioned in the previous sub-section, neuroscientists typically consider plasticity within a complex system. Plasticity of a complex system refers to the plasticity that can be an emergent phenomenon that arises due to the interactions of its parts. Plasticity within a complex system refers to the plasticity that is already embedded in the parts. Is it possible that the plasticity of a complex system emerges due to the inherent plasticity within the complex system (i.e. the plasticity cascades from a smaller scale to a larger scale)? In our universe, more complex structures arise from atoms to molecules, from nonliving to living, simpler organisms to larger animals, and from humans to socio-cultural structures. It appears that, particularly at the levels of complexity found in living systems – such as cells, brains, animals, and cultures – plasticity can be observed at each hierarchical level of these complex structures. For the complex systems that relate to lives, we focus on complex adaptive systems first and return to the discussion of how plasticity can cascade through scales.

Complex adaptive systems are types of complex systems in which the components adapt or learn in response to interacting with other parts (Holland 2014) and with their environment, which includes life and is also relevant for physics. When complex adaptive systems encounter certain external influences (e.g. an environmental change, feeding new information), by definition, they will try to adapt while keeping their identity or functionality. To do so, it may change its form by rewiring the interactions between parts and/or modifying the parts. An interdisciplinary perspective from anthropology similarly frames life as ‘the generative capacity of that encompassing field of relations within which forms arise and are held in place’, emphasising ‘the fluxes and flows of materials’ rather than ‘materiality’ itself (Ingold 2010). Such perspective complements the process of constantly changing forms of a complex adaptive system by rewiring its parts and their interactions as a network when encountering external influences. But whether such change is permanent when the external influence is gone (a plastic deformation) depends on the nature of the complex system and the nature and the degree of the external influence. Therefore, in our above definition, a complex adaptive system may not always show plasticity but can still show elasticity. However, the complex adaptive systems, especially lives such as cells, brain, animals, human, and culture, show a certain degree of plasticity when encountering large enough external influence.

Returning to the discussion of plasticity cascades across scales, plasticity might cascade through scales between hierarchical complex adaptive systems if the interactions between the sub-complex adaptive systems can also give rise to emergent phenomena (i.e. a complex system as a whole). An example from neuroscience is that synaptic plasticity gives rise to the plasticity of the whole brain. From a physics point of view, a more rigorous theory needs to clarify the necessary and sufficient conditions for plasticity to be able to cascade through scales in general complex systems.

At a certain level of complexity, the ability of a complex system to undergo irreversible deformation (i.e. plasticity) is also related to the notion ‘tipping point’, since it refers to a particular ‘point’ beyond which the system irreversibly changed. In physics, when the system parameters, or factors that influence the behaviour or characteristics of a system, change or cross critical threshold(s), a system can undergo phase transitions. In social sciences and complex systems literature, these phenomena are termed ‘tipping points’, although this term is not often used in physics. For example, a magnetic material becomes magnetised when its temperature, a system parameter, is below a certain critical temperature (Chandler 2009; Thurner, Klimek, and Hanel 2018). Changing system parameters may change the energy landscape. This can lower the energy barrier and allow the system to transit from one state to another (Otto et al. 2020). In relation to the plastic deformation of a complex system, it can refer to the external influence that led to the change of system parameters and thereby change its form irreversibly through tipping points.

Finally, noise – a specific form of stochastic influence in a system – appears to be relevant to plasticity from a physics perspective. As noted, stochasticity, or random fluctuations, plays a role in cognitive plasticity. In complex systems, noise can sometimes induce a large response by changing the energy landscape. This mechanism is related to stochastic resonance, where the presence of noise counterintuitively amplifies a weak signal, leading the system to undergo resonance-like behaviour (Gammaitoni et al. 1998). For example, the Atlantic Ocean circulation can be excited by abrupt, short warming events at the Greenland ice core (i.e. noise), inducing a switch from a stable to a weakly stable state, effectively inducing a tipping point (Ganopolski and Rahmstorf 2002). Sometimes, inherent noise, which arises from within the system itself, can induce tipping points endogenously without external forcing. This has been studied by examining information flows in networks, where noise – represented as nodes – can propagate short-lived fluctuations to temporarily destabilise neighbouring nodes, triggering a domino effect (van Elteren, Quax, and Sloot 2024).

Since inducing tipping points of a complex system implies a plastic change, external and/or inherent noise that induces tipping points plays a role in enabling plasticity of a complex system through, for example, stochastic resonance. Applying this to social systems, human communication involves information flow through social networks and social media. Hypothetically, noise could be (mis)information that propagates and induces a domino effect through the network, altering the overall structure of people's opinion on certain topics, inducing a tipping point (and thereby a plastic deformation) (Bak-Coleman et al. 2021). One may say a population is very plastic regarding opinions if only a small amount of external noise in the form of (mis)information can induce such change.

Grounding in Cultural Theory: Plasticity and Relationality – the Cultural Theory Version of Complexity

From a cultural theory perspective, we will show how scientific ideas on plasticity enter into a cultural sphere, where they also crystallise into imaginaries about different kinds of politics. This becomes particularly evident if one takes a relational approach, which, we argue, is the terminology within cultural theory that comes close to what in other disciplines is called a complex adaptive systems approach. Trownsell, Behera, and Shani (2022, 787) describes a relational approach as an approach that pays attention to phenomena as ‘always emergent’ and ‘co-constituted through relations’. Relationality is about how entities and identities emerge through different dynamics of relation (Barad 2007; Emirbayer 1997; Trownsell, Behera, and Shani 2022), an insight that derives less from nineteenth century hermeneutics of meaning and more from the semiotic pragmatism of Charles Sanders Peirce through to contemporary theorists of biosemiotics such as Eduardo Kohn. Even if the cultural sphere of meaning making cannot be represented in a network, a relational approach understands its subject in an analogical manner to how Peter Sloot describes a complex adaptive system, namely as ‘not reducible to its elements’ and ‘interacting elements that adapt to the environment they themselves create’ (see min 23:00; Center for Unusual Collaborations 2023). Because cultural meanings do not inhere in words and things, but emerge through relations, meanings also constantly evolve. As work in semiotics has shown, meaning is enacted through the dynamic interplay of humans, signs, and material environments (Malafouris 2015). Taking a relational approach to understand plasticity within the field of cultural theory is less about tracing shifting linguistic definitions of the concept and more about understanding how the cultural and political sphere itself exhibits plasticity, or how imaginaries, practices, and institutions emerge, adapt, and take on new forms in different relational contexts.

To understand how the meaning of plasticity evolves in relation to its cultural contexts, and thus works according to the logic of complexity, the writings of H.G. Wells serve as a case in point. Primarily known as a Science Fiction writer, in his career, Wells also wrote a biology-inspired non-fiction piece on ‘The Limits of Individual Plasticity’ in 1895 (Wells 1975). Cultural theorist Brown notes that Wells’ primary fascination with plasticity was that it ‘made life-forms potentially manipulatable’ (Brown 2021, 116). Brown also traces an underlying eugenics ideology, which also features in Wells’ fiction works The Time Machine in 1895 and The Island of Dr. Moreau in 1896 (Wells 1975). In Wells’ writing, plasticity does not invite plural possibilities of how the human may develop, but follows what Brown identifies as a eugenics perspective concerned with keeping the species from ‘degeneration’ (Brown 2021, 117).

With a similar critical sensibility to Brown, political theorist Mbembe analyses the experience of the black colonial subject. He notes that black bodies were treated as having a ‘quasi-infinite potential of transformation and plasticity’ (Mbembe 2019, 164). Also here, malleability serves power. These two references point to a repressive cultural understanding of plasticity. Significantly, these meanings emerged in relation to dominant ideas of political order at that time (including eugenics and white supremacy), rather than being inherent to the concept of plasticity.

What further demonstrates the relational nature of these specific understandings of plasticity (and by extension a ‘complex’ understanding) is that from the perspective of those who were repressed by the previously outlined political understanding of plasticity – plasticity came to mean something else. Mbembe writes that for the black colonial subject, being treated like a plastic human was not just a question of being passively moulded. Within the language of physics, we can think of this change as endogenous, that is, without external forcing. The genre of Afrofuturism, for instance, is a way to re-write this experience in a liberatory note (Mbembe 2019, 164). Brown, drawing also on Landecker, dwells on the question of how plasticity could also be an invitation for ‘utterly new mode(s) of existence for human matter’ (Landecker qtd. in Brown 2021, 111). This is a search for a plasticity that decentralises the eugenics ideal of the human as being white, male, and able-bodied, and amplifies alternative subjectivities and ‘other forms of belonging and relationality’ (Brown 2021, 112). Brown further underpins this idea with Malabou's notion of ‘neuronal creativity’ (Brown 2021, 115). Here, Malabou uses the term metaphorically: just as neuronal connections can reconfigure in response to input, cultural meanings may also shift unpredictably in the ‘space between’ interlocutors. This is not to suggest that semantic meaning exists at the neuronal level, but that cultural meaning too can exhibit an open-ended, relational form of creativity. For example, the meaning of vegetarianism has shifted from being framed as unmasculine or marginal to being recast as environmentally responsible, illustrating how cultural meanings plastically change in context. Brown explains, to Malabou, neural creativity emerges in the space between emitter to receiver where meaning may plastically change in the process (Brown 2021, 115). Thus, while context matters in the production of meaning it is not determinant. New and unpredictable meanings can emerge, rendering the cultural signification of plasticity a complex process.

Grounding in Public Health: All About Complexity

In contrast to neuroscience and cultural theory, complexity – rather than plasticity – is the concept that helps public health researchers make sense of their subject matter. Also, although there is a great deal of conceptual overlap with physics in terms of understanding networks and feedback loops, the terminology employed in public health is somewhat different. Public health researchers generally use the term ‘complex systems approaches’, rather than complexity or complexity science. The field generally emphasises the lens through which we view and understand the world, rather than the methodological innovations that are used to make these observations. Taking a complex systems approach is a relatively new, but increasingly popular approach because of its suitability to the types of issues public health researchers address (Huiberts et al. 2024; Mudd et al. 2024).

In public health, researchers are often concerned with understanding or addressing health inequities, or differences in health outcomes that are systematic, unjust and modifiable, like differences in lifespan between people with high and low education levels (Marmot 2005). These problems are often conceived as ‘wicked problems’, or those that lack a clear solution, have multiple stakeholders, have drivers and outcomes that interact with one another, evolve, and have no clear end (Wistow et al. 2015). To fully grasp these problems in all of their messiness, it is critical to take a holistic approach to studying them.

A complex systems approach helps us do this, by better understanding public health problems and how to address them. This approach equips us with the perspective to view health problems in the contexts in which they appear. This involves looking at the system as a whole, with many different interacting parts (Rod et al. 2023). Taking a systems view is in contrast to unidirectional statistical analysis, where we typically explore one or two determinants of a health outcome (Øversveen et al. 2017). Mapping a system in which a health problem arises, in turn, helps to design more effective interventions to tackle these issues (Kiekens, Dierckx de Casterlé, and Vandamme 2022).

Much like in physics, public health researchers are often interested in the behaviour of networks. Public health researchers, however, tend to focus on the properties and behaviours of social networks, exploring topics such as: (a) how health behaviours spread through social networks, and (b) how networks can be leveraged in health programmes to encourage health-promoting behaviours, and mitigate health-decreasing ones (Kaan et al. 2025; Valente 2012). Complex systems approaches are especially well-suited to this. Simply put, social networks are interconnections among different actors. When we study social networks, we are also generally interested in emergent behaviour, in which different interactions among individuals produce different results in different behaviours of the network (Mkhitaryan et al. 2019). Social network analysis within a complex systems framework enables us to do so.

A complex systems approach also gives us methodological tools to contend with non-linearities, feedback loops, and emergent properties. These tools include group model building, which is a structured qualitative process of leveraging the lived experience of a phenomenon to map it within a given system (Vennix 1999). The end result of a group model-building session is a conceptual model representing how different interacting parts within a system give rise to a given phenomenon. This moves beyond traditional qualitative research, as the focus is on understanding dynamic relationships that are identified alongside stakeholders. Simulation models, rather than inferential statistical ones, are also increasingly used in public health (Tracy, Cerdá, and Keyes 2018). This allows us to move beyond unidirectional linear relationships, and allows us to compare actual and hypothetical scenarios. The latter point is critical in public health: we do not actually have to conduct an intervention, for instance, to gain insight into whether or not it would be effective. This has the potential to dramatically increase the effectiveness of interventions once they are actually implemented (Smith et al. 2014).

Plasticity, on the other hand, receives scant attention in public health. This is surprising, given that we are often interested in exploring how and why individuals can change behaviour or practices. For instance, how diet change can be made permanent is something public health researchers are deeply interested in (Thompson, Zhu, and Moore 2025). However, the idea of plasticity has, to our knowledge, not yet been applied in this discipline. From a public health perspective, a complex systems approach helps make sense of a given health problem and identifies entry points for changing it. Plasticity might help describe how that change occurs and is maintained over time.

Perspective Taking: Applying Plasticity and Complexity to the Case of Plant-Based Diet Adoption

To illustrate how the concepts of complexity and plasticity may converge and diverge, as well as be used on various levels, we explore a case study that relates to our four diverse disciplines, among others. Methodologically, we take a perspective by providing interdisciplinary insights from the viewpoint of each discipline, while referencing each other's disciplines, and with a particular view to how they might connect to one another.

We focus on plant-based diet adoption, or choosing to eat plant-based in the first place, and maintenance, or continuing to follow a plant-based diet. We define plant-based diets as including vegan, vegetarian and low-meat flexitarian diets. This topic is a pressing one: today, in high-income countries, meat consumption is persistently high and has negative human and environmental consequences (van den Berg et al. 2022). A widespread social shift to plant-based diets would reduce greenhouse gas emissions as a result of meat production, and decrease rates of chronic diseases, such as type II diabetes and cardiovascular disease (Medawar et al. 2019). It is therefore critically important to understand why people decide to adopt plant-based diets and how these choices are maintained.

In particular, social networks play a crucial role in both plant-based diet adoption and maintenance, as peers, friends and family make similar health-related choices. Social networks composed of vegetarians may encourage individuals to change to vegetarian diets, while those without vegetarians may make vegetarian diets harder to adopt in the first place and maintain. However, exactly why social networks are involved in plant-based diet adoption and maintenance is not clear. Much of the literature on this topic is qualitative and highlights that social networks are an important influence on plant-based diet adoption and maintenance (Lopez, Sirvinskas, and Sutliffe 2023; Reipurth et al. 2019; Salmivaara et al. 2022). Few studies on the topic are quantitative (Hodson and Earle 2018), and rarer still are studies that are longitudinal (e.g. Thompson, Zhu, and Moore 2025). There are also precious few simulation studies on this topic, so that different mechanisms explaining why plant-based diets are adopted and maintained might be tested. However, these models are all hypothetical: none use real-world data, so they are unlikely to reflect the complex individual, social and structural factors known to influence diet choice (Elliot 2022; Taillandier, Salliou, and Thomopoulos 2021). There is work to be done to understand how social networks influence vegetarian diet adoption.

Considering the topic from a complex systems lens may help us consider the various interacting parts and feedback loops that contribute to plant-based diet adoption and maintenance, and how a once-fringe idea may diffuse through social networks to become the norm. Considering plasticity may help us to explain why, once made, a diet change may become permanent. Below, we each explore how complexity and plasticity may relate to this topic, from within our own disciplinary perspectives. We also consider how plasticity and complexity may be present at different levels: micro (individual), meso (household and social network), and macro (market, media, and policy) levels, tracing the cross-level interactions that connect them.

A Neuroscience Perspective: Plasticity of Social Circles and Neuronal Ensembles as Units of Change of Habit

Neuroscience can help us understand how social behaviour is adopted and ingrained at the micro-level by leading us to a few plasticity-related complex concepts integral to plant-based diet adoption. Given the interdisciplinary nature of this article, we focus on two aspects that help us understand the issue from a public health perspective. We note that neuroplasticity related to habits is directly linked to changes in diet, forming a nested plasticity with the plasticity of social networks during plant-based diet adoption.

Nutrients in our diet can send signals to our brain and are known to converge on metabolism and synaptic plasticity, which reciprocally regulate each other. The hypothalamus, a region of the brain, plays a central role in this process (Gómez-Pinilla 2008). Let us discuss how the microbiome, social cues and neuroplasticity can be linked to solidify these concepts. Eating behaviour, which often takes place in a social setting, such as a family dinner, provides a plastic environment for us to change our food habits. This change may be the adoption of a new diet, which can be strengthened by positive or negative feelings associated with family gathering (a form of associative learning). On the other hand, a simple conversation at dinner may impact personal choices. Climate change and the choice of eating meat are often discussed in public, which may alter the response of the guests to the provided vegetarian stew with positive reinforcement. The warm environment of the room, combined with a reward for the hard work of dinner preparations, will be remembered; this might, even subconsciously, lead to a change in behaviour. Moreover, the food that we consume on this dinner table can also lead to a change in our behaviour through molecular and cellular mechanisms. For instance, unsaturated fats, such as the essential fatty acid omega-3, that are rich in (but not restricted to) the plant-based diet can enhance cognitive performance and by directly affecting the fundamental cellular process of gene expression, increase synaptic plasticity. On the one hand, a molecule called BDNF, central to synaptic plasticity, is critical to learning and engages with energy metabolism, and is directly influenced by a plant-based diet (Gómez-Pinilla 2008; Murphy, Dias, and Thuret 2014). On the other hand, nutrients that constitute a new diet may indirectly affect the body and the brain. Microorganisms in the gut, collectively called the microbiome, affect vitamin production. Hormones released from the digestive system, among others, are sensitive to such dietary changes (Maqsood and Stone 2016). A diet rich in fibre, such as the regular consumption of the stew served at dinner and similar dishes, can promote the growth of a distinct community of gut microbiota. Eventually, neuroplasticity is induced by a change in behaviour as a result of the dietary plasticity of a social network. Thus, switching to a plant-based diet may alter cognitive function and disease susceptibility through independent mechanisms.

An increase in plasticity in the brain thus opens a window to change habits. Therefore, early childhood and adolescence, where neuroplasticity is very high, present opportunities to alter dietary preferences (Kolb and Gibb 2011). The interaction of social cues, nutrients, microbiome, rituals, and food intake forms complex feedback and feedforward loops, the outcome of which is not always predictable. The choice also depends on an individual's state of mind, which may shift from conservative to curious due to changes in existing social circuits or joining a new one. We cannot miss the dependence of different types of plasticity – at the level of the microbiome, synapses and social networks – that behaviour is entangled in.

Social networks strongly influence behavioural change, which is inherently linked to neuroplasticity, itself a form of nested plasticity. Learning how habits are formed from a neuroscience point of view can help us understand how to modulate the social interactions that eventually will lead to plastic transformation of social networks. The inner workings of the brain may shed light on how plasticity may be relevant for public health. Typically, and most commonly, neuroplasticity occurs at the level of connections between neurons. The strength, path or way neurons communicate is altered in neuroplasticity. It is tempting to draw parallels to interpersonal communication; however, a plastic change in social networks does not necessarily alter the way people communicate. Rather, communication is more of a means of transferring habits. Since a change in societal dietary preference will occur at the level of communities, the plasticity of neuronal ensembles represents a better comparison. While individual neurons can change their receptiveness to signals or synaptic connectivity, a change in the functional output of the neuronal ensemble is what will cause a change in an individual's behaviour (e.g. on whether to find meat rewarding), leading to neural plasticity (Hansel and Yuste 2024).

To draw a parallel, social networks are organised with similar principles as one person taking action influences others. We reason that a persistent change in societal-level dietary preference, which may be induced at a macro-level, e.g. through a governmental campaign, will eventually occur at the level of social circles rather than individuals or individual connections. This is akin to neural plasticity at a network level, which cannot be explained solely by cellular or synaptic changes. For instance, shifting from following a YouTube channel dedicated to barbecue cooking to one led by an influencer promoting locally sourced, plant-based foods, and thereby joining a new digital social circle, can reinforce long-term changes in an individual's behaviour. Just as a memory can recruit a neuron in a new network, the news of a new trend can be the social cue to induce plasticity in the choice (or the composition) of social circles. Thus, complexity of society and the brain may be self-organised based on similar unintentional local principles that use plasticity to achieve impact that only makes sense at the system level.

A Physics Perspective: Applying Networks, Plasticity and Tipping Points to Plant-Based Diets

Here we consider the case of a widespread shift to plant-based diets and examine the relationships between complex systems and plasticity from a physics perspective with particular attention to network theory and tipping points (Eker, Reese, and Obersteiner 2019).

From a physics point of view, an individual's social network is a complex system in which: (a) each person can be characterised by the extent to which their diet is plant-based; or (b) the belief or attitude network on the choice of eating plant-based (Maas, Dalege, and Waldorp 2020). If a person's entire social network eats plant-based, the social pressure to eat plant-based may reinforce a person to adopt a new diet or maintain an existing one.

For a belief network (e.g. a node of implementing a plant-based diet can be connected to another node of the desire to lower carbon emission), having conflicting beliefs in the mind of eating either plant-based or omnivorous is less stable than the beliefs being aligned with each other. Individuals can interact with each other and exchange thoughts and values, influencing each other's network of beliefs. For example, if a member of a social network interacts with an activist (e.g. a pro-vegetarian one), it is possible that one's belief network can tip from one state (not having a strong opinion towards a topic) to another (becoming strongly for or against it) because of the increased attention to the topic (Maas, Dalege, and Waldorp 2020).

For some, this might encourage more people to adopt plant-based diets. For others, it might also have the opposite effect. Anthropological work on schismogenesis describes how social groups may not only align internally but also deliberately differentiate themselves in opposition to others. As Wengrow and Graeber (2018) demonstrate in their study of Pacific Coast foragers, practices such as slavery crystallised through relational dynamics of contrast, rather than being adopted or rejected in isolation. Hypothetically, this polarisation could result in changing social networks, as people may increasingly be attracted to others with similar opinions and stay away from those with opposing views. On the other hand, in the model of van der Maas, perturbing vegetarian agents ‘in the direction of the meat-eating leads to a slow convergence to the V [vegetarian] state in the population’. This highlights the complexity of network dynamics and interventions.

In an attempt to harness the nonlinearities to drive social change to tackle climate change, the notion of ‘social tipping points’ or ‘social tipping dynamics’ has been adopted rapidly (Milkoreit 2023; Otto et al. 2020). Social tipping points’ implications for plant-based diets have also been discussed (Aschemann-Witzel and Schulze 2023). Extending the tipping point framework to the networks in this example, changing certain parameter(s) of the system (e.g. social norms around plant-based diets, or the cost and availability of plant-based foods) may lower the energy barrier and lead to a tipping point of individuals transitioning from omnivorous to plant-based diets, and cascades through the social network (e.g. through social contagion, see Aral and Nicolaides 2017 for the case of exercise). This may help tip a population that is predominantly omnivorous to one that is predominantly plant-based. Therefore, analogically, one can ‘engineer’ the networks to become more plastic by changing these system parameters.

But to make the social network more plastic, what parameters must be changed and how can we change them? Social tipping interventions were suggested to achieve these ends. These interventions ‘have the potential to erode the barrier through triggering social tipping dynamics in different sectors and thus paving the way for rapid transformative change’ (Otto et al. 2020). Social tipping interventions may be found through analysing the system through constructing a causal-loop diagram to trigger certain feedback loops, and/or with expert elicitation (Eker, Reese, and Obersteiner 2019; Otto et al. 2020). An insightful example listed in Aschemann-Witzel and Schulze 2023 includes making policies to transparently show how many others have already shifted preferences may speed up the change for social norms (Andreoni, Nikiforakis, and Siegenthaler 2021). Linking this back to the terminology of complex systems, these social tipping interventions may act as social noise to induce stochastic resonance (Ganopolski and Rahmstorf 2002) as discussed in Section 2.2 such that the energy barrier can be lowered (Otto et al. 2020). Here, the transparent policy changes how the information exchange between the parts in the social network, which can also be seen as a kind of ‘noise’ to perturb the system, may enhance the plasticity of the system to undergo a tipping point.

A Cultural Theory Perspective: Destabilising Cultural Meanings as Enhancing Plasticity Within Complex Adaptive Systems

At a macro-level, cultural theory helps us understand how a new behaviour – plant-based diets – may become ingrained in society. The physics approach to social networks already drew attention to the importance of beliefs and attitudes. From a cultural theory perspective, we can further understand how diet is related to other cultural meanings, just as the meaning of plasticity needs to be understood in a relational way, which we suggest is analogous to the dynamics of a complex adaptive system. This means emphasising relations over identity, and emergence over essence. As shown before, these relations are not neutral but embedded within power relations.

The Nobel Prize-winning novel The Vegetarian (in Korean 2007) (Han 2016) by Han Kang illuminates these complex entanglements of meaning in a very brutal way. It tells the story of the transformation of a Korean woman who decided to become a vegetarian and the response of her family against her choice. While The Vegetarian is a fictional story, it surfaces, exaggeratedly, some possible cultural meanings that a simple choice of refusing to eat meat may entail. From the perspective of her familial environment, the protagonist's choice to eat vegetarian is connected to her non-conforming femininity. Refusing to eat meat during a family dinner with her parents and refusing to cook meat for her husband means that she is failing to be a good wife and a grateful daughter. These normative constraints on what an action pragmatically signals and means recur in the coercive reaction she feels as a subject of an environment that is actively reading her and ascribing normative meaning to what she understands as a private matter. Conversely, from the perspective of the protagonist, the refusal to eat meat is also a refusal to tolerate the violence she witnessed as a child against animals, a refusal to let her body be controlled by men but also conceptions around sanity by medical institutions. She searches for life outside this system, which sparks in her desire to become like a plant. The novel tragically ends with the protagonist – against all efforts of the environment – succeeding to starve herself to death, a transformation that perhaps brings her closer to the metabolic processes of a plant. It is a clear example where the dynamics of repression and liberation structure the transformation process that the protagonist desires. How can we further understand this struggle about the cultural meaning of a diet change through plasticity?

As Peter Sloot mentioned in his presentation during the plasticity symposium, a network, which to him is an effective representation of a complex adaptive system, that is being disturbed in some way (i.e. rewiring a node, adding noise, perturbing the system), has a better performance of sending a message from one side to the other, and thus showcases a higher degree of plasticity (see min 28:00–31:00 min of Centre for Unusual Collaborations 2024). In other words, a complex system that is already moderately ‘shaken up’ from the inside deals better with external influence without collapsing in its entirety.

Analogously, in the case of The Vegetarian, from a cultural theory perspective, the meaning of diet is connected to other cultural meanings (gender-conformity, accepting familial hierarchies, tolerating violence) and cannot be reduced to an individuated response calculus. Meaning is reticulated through scales of social structures, and this insight is drawn from social theory (see Gallagher 2013) as much as the semiotic pragmatism informing contemporary theories of multi-species worldbuilding (see Kohn 2013; Povinelli 2016). As long as these multiple connections around diet are strong and remain undisturbed, changing one's diet is exceedingly difficult, because it then coincides with rejecting a closely knit together network of values (Ferzacca 2004). On the contrary, if the meaning of being vegetarian is decoupled from specific cultural meanings and other meanings like what it means to be a daughter and wife become destabilised, turning vegetarian becomes a smaller question, because it is not necessarily related to other cultural meanings. This shows, then, that the relational nature of cultural meanings interacts with each other, analogously with the dynamics of a complex adaptive system that displays plasticity. From a cultural theory perspective, we may then learn that diet change should not be conceived in a cultural vacuum but in relation to other cultural meanings and their changes and destabilisations.

Finding Common Ground: What Perspectives From Different Disciplines Can Bring to the Study of Plant-Based Diet Adoption

This interdisciplinary exercise emphasises that both plasticity and complexity are deeply relevant to understanding how individual behaviour change may ultimately translate to societal shifts. Within a complex system, with many different interacting parts and non-linear results, behaviours of individuals, social networks, and society overall may shift. Plasticity may be present at various levels of a complex system, as such shifts become permanent.

At the micro-level, plasticity is expressed in the brain and body as people learn, form habits, and update preferences. Insights from neuroscience help us understand how a new health-related choice can become a habit. Within us are tiny feedback loops, enabling us to more easily transition from one state (meat-eating) to another (vegetarian), and help explain why some behavioural states become habits, and others do not. A plant-based diet change may also have unforeseen consequences, such as increased or decreased disease susceptibility. Further, who might be best able to maintain a plant-based diet is in part determined by biological age. This plasticity is path-dependent and age-sensitive: younger people are often more susceptible to peer influence and more able to relearn tastes, whereas older adults may show greater inertia. Complexity appears even here, because dietary change can have unintended consequences that depend on composition and context, such as shifts in metabolic markers or disease risk.

At the network, meso-level, households, peer groups, and wider social networks provide the channels through which change spreads and stabilises. Networks seem to be crucial for fostering social change, and themselves are plastic. Ties strengthen or weaken, and local norms evolve as people observe, emulate, or resist one another. Networks are also complex: Non-linear contagion and threshold effects can generate clustering, polarisation, or tipping behaviour. From physics, we learn about how these changes may spread out from an individual through their social networks, and how networks and societies can exhibit plasticity, ultimately leading to a permanent change from most eating omnivorous diets to a majority of people eating plant-based diets. But what are the characteristics that make a network plastic? And is there a possibility that a network might be too plastic?

At the macro-level, culture, markets, and policy shape which lower-level changes (‘plasticities’) are expressed and sustained. From cultural theory, we are reminded that a transition to plant-based diets does not happen in isolation. Food choices and preferences are deeply culturally embedded. Changing the social importance of foods that might be objectively unhealthy or unsustainable but culturally considered to be good foods can be an incredible challenge. There is, of course, a gendered element to diet choice: women are much more likely to be vegetarians than men. Further, generally only the wealthiest, highest educated in society adopt plant-based diets. A transformation towards plant-based diets would potentially leave out the most vulnerable in society.

Taken together, a multi-level view makes explicit that plasticity and complexity are not properties of individuals or societies alone, but of nested systems with interconnected parts that adapt and interact. For instance, micro-level habit formation can be amplified or hindered by meso-level network dynamics, while macro-level institutions, markets and norms set the conditions that shape both. This perspective helps to clarify why some dietary shifts propagate and persist, why others stall or backfire, and where leverage points lie for equitable, lasting change.

Is fostering widespread change towards plant-based diets the stuff of fantasy? We argue that it is not. Society has already experienced numerous social transitions in which one state has permanently transitioned to another. For instance, until the late nineteenth century, garbage cans were unnecessary: food waste was fed to pigs. What was left was generally burned. Without single-use plastic (which did not come into use until the mid-twentieth century), there was little waste to dispose of. Within a few decades, it became impossible to imagine a world without an incredible amount of waste. If negative change can occur at such a rapid pace, positive social change – like reduced meat consumption – may also be possible.

Integration

Where is the plasticity in relation to a complex system? Most of our disciplinary and interdisciplinary interrogations seem to find plasticity within a complex system. Nuancing this further, perhaps plasticity is not in the system overall, but a specific (collective) synapse, neural network, behavioural or developmental pattern, social or belief network, or the social norms of individuals within a complex system. All these are related to micro-, meso-, and macro-levels, related to the power structure established throughout history. As plasticity can be an emergent property of a complex system, the plasticity at one scale can emerge from the interactions between parts at other scales, resulting in ‘propagating plasticity from one scale to another’. The feedback between these different levels can produce a meta-plasticity of the system (Aston 2019; Malafouris 2015). Our integrated work suggests that plasticity is an integral property of complex systems.

In our case, plasticity can be boiled down to the ability to change habits, at individual, social network and societal levels. People easily establish habits but infrequently change them. We learn that the change at the level of an individual should not be viewed as an isolated event. This change is likely spurred by changes in their broader social contexts, either on a network or societal level. Still, this small change may have cascading effects that grow over time. Crucially, systems also exhibit meta-plasticity – their capacity to change their capacity to change – for example, learning-to-learn in individuals, shifting receptivity and thresholds in networks, and institutional flexibility in organisations and governments. Meta-plasticity helps explain why some shifts stick and scale while others are abandoned, or fail to make a large impact. An intriguing question raised by this discussion is whether certain configurations of variable plasticities, such as high network plasticity combined with moderate institutional flexibility and ecological elasticity, might be optimal for promoting resilience or strategic interventions. Interactions among these different plasticities could themselves give rise to stochastic resonances that amplify adaptive change, contributing to the system's broader meta-plasticity.

This interdisciplinary exercise has sharpened our view that plasticity can be a property of a complex system. This observation gives us the possibility to transfer tools and concepts between fields to gain a mechanistic understanding of plastic changes, and the power to foster or mitigate them through foresight and planning.

Our interdisciplinary approach to understanding plasticity and complexity in relation to one another is also promising. Disciplinary insights into the mechanics of complex, plastic systems show how plasticity may be present from the neuronal level to society at large. However, we ultimately observe that the plasticity at these different levels is able to interact and to form a meta-plasticity of complex systems. Such an observation is much more difficult to make when working from within disciplinary siloes. Further, we attempt to show how plasticity and complexity can be applied across disciplinary borders. In literature from different disciplines, we see multiple, sometimes inconsistent uses of both complexity and plasticity. Engaging with other disciplines to create a shared, interdisciplinary vocabulary may meaningfully add to our understanding of how systems can achieve lasting change.