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The Economy as an Evolving Complex System IV, published by the SFI Press in February 2026, is the latest in a series originally launched nearly four decades ago to rethink economics through the lens of complexity science. Rather than assuming markets always balance neatly, the book treats the economy as a living system that grows, changes, and reacts in ways that are hard to predict.

A century ago, the section of U.S. federal law governing public health and welfare was relatively small and loosely connected to the rest of the legal system. Today, it is one of the largest and most interconnected parts of the United States Code. That shift is one of many patterns revealed by a new dataset published in the journal Scientific Data, which reconstructs the U.S. Code — the official compilation of federal statutory law — from 1926 to 2023.

Whenever an authority has influence over a population — be it a social media platform moderating user comments, a government imposing laws on its citizens, or an employer placing restrictions on employees — some people will push back against the authority’s rules. In a study recently published in PNAS, SFI External Professor Stephanie Forrest and her colleagues devised a model for the give-and-take between dissenters, who break the rules, and authorities, who impose punishments.

Figures such as a country’s gross domestic product or a city’s population size represent organizational and individual decisions over time. These statistics are useful for policymaking, but they hide the complexity that stems from regional variations in choice. Program Postdoctoral Fellow Jordan Kemp hopes to leverage the richness of urban-growth data by capturing patterns of behaviors among different groups at various scales, from the individual to the population level.

We trust our memories because they feel natural, and we trust time because it seems to flow in only one direction. Physics, however, allows for stranger possibilities that challenge our intuition.

In a new paper, SFI researchers examine the Boltzmann brain hypothesis, a long-standing thought experiment that raises fundamental questions about memory, entropy, and the direction of time. The work clarifies how arguments for or against these ideas depend on assumptions about the past that are not fixed by physical laws alone.

A new study co-authored by SFI External Professor Laura Fortunato (University of Oxford), challenges a long-standing claim that polygynous marriage, where men have multiple wives, creates a surplus of men with no prospect of ever marrying. Counter to a widespread belief that a large contingent of unmarried men leads to negative social outcomes, including interpersonal violence and, in extreme cases, civil conflict, the research finds that polygyny often coexists with high rates of marriage among men.

A December 10–12 working group met to bring together researchers from two fields — neuromorphic computing and stochastic thermodynamics — to think about ways our built computers might replicate the energy efficiency of biological brains. 

Francis Spufford, an internationally award-winning writer of nonfiction and fiction, has joined SFI as Miller Scholar. A Fellow of the Royal Society of Literature, Francis Spufford teaches writing at Goldsmiths, University of London, and is the author of several books, including Red Plenty, Golden Hill, and, most recently, Cahokia Jazz. 

In late December 2025, SFI External Professor Wendy Carlin was appointed the title Dame Commander of the Order of the British Empire, among the highest honors in the British system, for her wide-ranging research in economics.

A popular vision of life after climate action looks like vegetarians riding bikes, city centers without cars, and people foregoing air travel. But a paper published in Nature Sustainability finds that climate policies targeting lifestyle changes (say, urban car bans) actually weaken people’s green values, thereby undermining support for other needed environmental policies.

Biologists at UCLA used a natural experiment during the COVID-19 lockdowns to study the effects of human activity on urban wildlife. In a new study, SFI External Professor Pamela Yeh and co-author Eleanor Diamant describe one such impact: a rapid change in the beaks of black-eyed juncos.

Every task we perform on a computer requires different components of the machine to interact with one another — to communicate. But scientists don't fully grasp how much energy computational devices spend on communication. Now, a new study in Physical Review Research sheds light on the unavoidable heat dissipation that occurs when information is transmitted across a system.

SFI Research Fellow Anthony Eagan reflects on SFI's new multi-day event, Synthetic Imagination, which launched in September. This year's event, co-organized by Eagan and SFI Director of Experimental Projects Caitlin McShea, convened a series of presentations around the theme of imagination and architecture. 

"Over the past 40 years, the field of microeconomics has gone through a revolution in real-world applications, yet the theoretical models taught in Ph.D. coursework have been slow to catch up," writes SFI External Professor Suresh Naidu in a review of a new textbook by SFI Professor Sam Bowles and Weikai Chen, a professor of economics at Renmin University of China. "Allocation, Distribution, and Policy is an entry into a long-standing effort to build a new paradigm in economics."

The simulation hypothesis — the idea that our universe might be an artificial construct running on some advanced alien computer — has long captured the public imagination. Yet most arguments about it rest on intuition rather than clear definitions, and few attempts have been made to formally spell out what “simulation” even means. In a new paper, SFI Professor David Wolpert introduces a mathematically precise framework for what it would mean for one universe to simulate another — and shows that several longstanding claims about simulations break down once the concept is defined rigorously.

For most of human history, large societies have drawn clear lines between people who belong to the in-group and those who do not. These lines determine who is recognized, protected, or granted status, and who is excluded. But starting during the Enlightenment period, European societies and their offshoots began relaxing the rules around who was granted fundamental rights and protections, a development many scholars see as essentially unique in human history — one that has grown steadily over the past several centuries and continues today. 

In October, the International Society for Artificial Life recognized several SFI researchers and co-authors with the ISAL Award for Outstanding Publication of 2024. The award celebrates the paper “Fundamental constraints to the logic of living systems,” which was published in Interface Focus last fall.

An Introduction to Ergodicity Economics is a new textbook that draws on physics to re-examine traditional economic theory. It begins with flipping a coin. And a hypothetical gambit. Imagine you were offered the following: Every time the coin lands on heads, your wealth increases by 50%. And every time tails comes up, your wealth drops by 40%. Should you accept? That depends on how you look at the predicted outcomes of this random system, says SFI Professor Ole Peters, a physicist at the London Mathematical Laboratory, who co-wrote the textbook with former LML colleague Alexander Adamou.

Three SFI External Professors and their collaborators received a 2025 SAF Research Award from the Shanghai Archaeology Forum for their ongoing project, “The Global Dynamics of Inequality over the Long Term.” The collaboration, nicknamed the GINI project, was one of 10 international projects celebrated at the SAF annual meeting in Shanghai this December, selected from 140 nominations.

When scientists test algorithms that sort or classify data they often turn to a trusted tool called Normalized Mutual Information (or NMI) to measure how well an algorithm’s output matches reality. But according to new research, that tool may not be as reliable as many assume.