Day 1, May 11th:

9.30-9.40: Opening speech by Stefan, president of CSH

9.40-10.20: Wout Merbis “Hyperscaling relations of spatial fluctuations in urban populations"

10.20-11.00: Rafael Prieto-Curiel “A radial analysis of urban segregation”

11.00-11.30: Coffee break

 

11.30-12.10: Stefan Thurner (TBA)

12.10-12.50: Fariba Karimi (TBA)

12.50-14.10: Lunch Break

 

14.10-14.50: Jay Armas “Society as a phase of matter”  

14.50-15.30: Frank Pijpers “Timeliness criticality and the economy” 

 

15.30-16.00: Coffee break

16.00-17.30: Panel discussion 1st, chaired by Mirta Galesic

 

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Day 2, May 12th:

9.30-10.30: Mirta and Henrik and their group “Collective adaptation of beliefs, strategies, and discourse”

10.30-11.10: Eddie Lee “Collective decisions in voting and moving" 

 

11.10-11.30: Coffee break

 

11.30-12.10: Mike Lees (TBA)

12.10-12.50: Jan Korbel “Drivers of Social Polarization: Insights from Social Connectivity and Campaign Influence”

12.50-14.10: Lunch Break

 

14.10-14.50: Han van der Maas “Psychological Networks: Zero Matters"

14.50-16.00: Panel discussion 2nd, chaired by Ben Meylahn

 

16.00-: Coffee Break and Farewell

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Talk abstracts:

Wout Merbis - Hyperscaling relations of spatial fluctuations in urban populations

The science of urban scaling has uncovered many striking regularities in cities, ranging from the scaling of socio-economic activity with population to fractal patterns in urban morphology. Yet most studies focus on how aggregate indicators scale with total population. In this

talk I examine cities as spatially extended complex systems and study how population fluctuations scale across spatial scales. Using high-resolution population grids, we apply a coarse-graining procedure analogous to a phenomenological renormalization group and measure how the mean and variance of population counts scale with aggregation size. This yields two exponents describing urban form (ω) and spatial fluctuations (ε). Across cities in the Netherlands, these exponents are not independent but lie close to a linear hyperscaling relation. The position along this line varies systematically with urban development level. Extending the analysis to hundreds of cities worldwide shows that the relation is robust but non-universal: its parameters vary across geography and drift over time. A theory based on long-range spatial correlations and the tendency of mature cities toward monofractal organization explains this behavior and predicts an asymptotic limit ε = 2+ω, consistent with the empirical trend. The resulting hyperscaling relation links urban morphology and fluctuations and provides constraints on mechanistic models of urban growth.

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Jay Armas - Society as a phase of matter

I’ll introduce a general hydrodynamic framework for modelling societal dynamics and show how it applies to a coupled system with Schelling- and voter-like dynamics that exhibits segregating and polarising macroscopic patterns.

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Frank Pijpers - Timeliness criticality and the economy

In socio-technical systems ”timeliness”, i.e., system elements being available at the right place at the right time, has been ubiquitously and integrally adopted as a quality standard. A variety of incentives, such as competitive pressures, prompt system operators to myopically optimize for efficiencies, running the risk of inadvertently taking timeliness to the limit of its operational performance, correspondingly making the system critically fragile to perturbations by pushing the entire system toward the proverbial “edge of a cliff.” I will discuss some of the modelling, demonstrating this is genuinely a critical phenomenon, as well as efforts at recovering the signal of 

this effect in empirical settings beyond the original motivating example of rail network operators.

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Eddie Lee - Collective decisions in voting and moving

At the Principles of Emergent Things (PoETs) Lab, we try to understand how collective outcomes derive from individual choices based on local information, heuristics, and constraints. I will discuss two ongoing projects. In the first, we show that polarized voting in the US Senate is more than increasingly rigid individual biases. We find that the context of the vote (e.g., procedural rules, issues up for vote) plays a dominant role in collective outcomes, and this leaves a quantitative signature in the entropy. In the second project, we show that large, intermittent, and periodic fluctuations in migration rates can come from individuals using social information to make a decision about to migrate or to not. This is in contrast with the focus on exogenous perturbations and highlights the importance of individual-level heuristics, often unmeasured and overlooked, in determining the impact of conflicts and natural disasters.

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Jan Korbel - Drivers of Social Polarization: Insights from Social Connectivity and Campaign Influence

Modern societies are increasingly characterized by rising political polarization. In this talk, we present a unified perspective on polarization as an emergent phenomenon driven by social interactions and external influence. We first show that increasing social connectivity, often assumed to promote consensus, can instead induce a transition toward strongly polarized states. Using a simple model that combines homophily and social balance, a critical connectivity threshold is identified beyond which societies abruptly split into opposing groups. We then consider polarization in elections, where voter behavior is shaped by both local social interactions and external campaign influence. It is shown that when campaign spending exceeds a critical level, the system transitions to a polarized regime in which social influence becomes negligible and outcomes reflect external alignment. This regime is further characterized by hysteresis effects associated with

incumbency. Empirical calibration with US House election data provides support for these predictions. These findings underscore the importance of systematically studying the mechanisms that drive polarization and the conditions under which they lead to abrupt collective transitions.

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Mirta Galesic - Collective adaptation of beliefs, strategies, and discourse

Individuals and collectives continuously adapt their belief systems, strategies that they use to connect to others and make decisions together, and the way they communicate with each other. We present an overview of related ongoing research in our group on collective minds at CSH. Beliefs in individual minds are related and can be represented as networks. The structure and dynamics of these networks can be studied on both individual and collective levels. We will describe two models of these belief networks studied in our group, including a unified model of psychological processes involved in belief dynamics, and a model describing mechanisms for link updating in belief networks. We will also describe several empirical paradigms for studying belief dynamics, including two novel paradigms for collecting empirical data about individual belief networks, and experiments to test statistical physics models of how social structure and agents of change shape collective belief dynamics. Finally, we will describe our ongoing studies on how groups adjust their decision-making strategies and discourse to changing problem environments. Ultimately, these and related efforts should help us to understand and adapt our collectives to better cope with ongoing societal challenges.

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Han van der Maas - Psychological Networks: Zero Matters

Psychological network theories provide an important alternative to traditional common cause theories, such as the g-theory of general intelligence and brain-based explanations of depression. Network theories, which are often formalized using the Ising model from statistical physics, have gained significant empirical support. However, the binary nature of nodes in Ising-type models presents a limitation, as many psychological data sets include responses with uncertain or neutral categories (e.g., “don’t know” or “not relevant”). Ternary spin models, such as the Blume–Capel model, overcome this constraint by incorporating a third node state, zero, that can represent such responses, enabling more nuanced scale representations. The resulting models exhibit more complex dynamics and provide new insights into research across a range of psychological constructs. We illustrate our approach with examples from three key subdisciplines of psychology. First, we introduce a ternary spin model for attitudes, extending the Ising attitude model. Next, we propose a unified framework encompassing both bipolar disorder and major depressive disorder. Finally, we present a novel ternary network model for understanding knowledge acquisition.

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Rafael Prieto-Curiel - A radial analysis of urban segregation

Cities provide access to essential services such as healthcare, education, transportation, water, and sanitation, but they also produce highly unequal and segregated spaces. A useful way to understand these inequalities is by considering the position of neighbourhoods relative to the city centre. In this talk, I will discuss this radial perspective to observe a city, showing that services and opportunities tend to cluster in central areas, while more remote neighbourhoods face greater poverty, weaker access to resources, and higher levels of social exclusion. Patterns such as lower access to water or household computer ownership in peripheral areas illustrate how segregation is embedded in the spatial structure of cities.