Tuesday, December 16, 2025

My Uncle Was a Matrix Multiplier


Turn people into numbers and make them do whatever you want!
 
The secret behind pedestrian crossings—and why some spiral into chaos
Mar 2025, phys.org

If you ever have the desire to just fuck shit up, now you know how:

The researchers found that for order to be maintained, the spread of different directions people walk in must be kept below a critical angle of 13 degrees.

When it comes to pedestrian crossings, this could be achieved by limiting the width of a crossing or considering where a crossing is placed, so pedestrians are less tempted to veer off track towards nearby destinations.

Based on their calculations, the researchers found that pedestrians are more likely to form lanes when pedestrians from opposite directions walk relatively straight across a road. This order largely holds until people start veering across at more extreme angles, of 13 degrees or higher. Then, the equation predicts that the pedestrian flow is likely to be disordered, with few to no lanes forming.

via University of Bath, MIT, and Academy of Physical Education in Katowice in Poland: Bacik, Karol A., Order–disorder transition in multidirectional crowds, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2420697122.



US political rhetoric: Analysis of 8 million speeches shows increased reliance on personal beliefs over facts
Apr 2025, phys.org

Researchers examined political rhetoric in 8 million speeches by members of the US Congress between 1879 and 2022 to see if the focus of their language was more on data and facts or personal convictions and subjective interpretations:
  • 49 keywords for fact-based language - "analyze," "data," "findings" and "investigation"
  • 35 keywords for intuition-based language - "point of view," "common sense," "guess" and "believe"
The team noticed a significant decline in the use of evidence-based political rhetoric since the 1970s, with a historic low in the present. Over the same period, the researchers observed a decline in legislative productivity, an increase in the political polarization of both political parties as well as growing economic inequality in the US.

After 1940, the balance tipped towards facts and peaked in the mid-1970s. From 1976 to 2022, however, there was a significant, continual decline in the use of facts in congressional speeches, with a historic low in the present. Both US parties are affected by this downward trend, although the drop has been even steeper for Republicans since 2021.

"One remarkable aspect of our results is the strong association between evidence-based language and performance. The more speeches in Congress reflect a reliance on evidence and facts rather than intuition, the better the performance of Congress and the less polarization between parties."

In many democracies, there is currently much concern about 'truth decay': the blurring of the boundary between fact and fiction, not only fueling polarization but also undermining public trust in institutions"

via University of Konstanz: Segun T. Aroyehun et al, Computational analysis of US congressional speeches reveals a shift from evidence to intuition, Nature Human Behaviour (2025). DOI: 10.1038/s41562-025-02136-2


How agricultural practices and governance have shaped wealth inequality over the last 10,000 years
Apr 2025, phys.org

They're using a new database of 27 scientists from around the world who analyzed about 47,000 houses from more than 1,700 archaeological settlements.

This study looks at wealth inequality and floor space by square footage.

"The emergence of high wealth inequality wasn't an inevitable result of farming. It also wasn't a simple function of either environmental or institutional conditions. It emerged where land became a scarce resource that could be monopolized. At the same time, our study reveals how some societies avoided the extremes of inequality through their governance practices."

They found that in regions with land-intensive farming systems, such as those with specialized animal traction for plowing, high wealth inequality became persistent, with a small number of households controlling productive land. In regions without traction animals, land became highly valued through terracing, irrigation or drainage. While such engineering projects could begin as cooperative endeavors, a minority of households often gained control of these landscapes.

The study shows how high wealth inequality emerged in diverse world regions. If land came under pressure, for example through local population growth, investments like terracing and irrigation or specialized plow animals boosted production, but also made land more valuable, fueling competition. Over time, larger settlements developed as hubs of wider settlement hierarchies and were sustained through land-intensive farming systems.

The findings challenge the idea that high wealth inequality is inevitable. Instead, it was often a localized consequence of expanding societies with a lack of political mechanisms to deal fairly with land constraints. 

via Oxford and Washington State University: Amy Bogaard et al, Labor, land, and the global dynamics of economic inequality, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2400694122


Archaeological database reveals links between housing and inequality in ancient world
Apr 2025, phys.org

This goes w the other article - "What we did was we crowdsourced, in a sense," Ortman says. "We put out a request for information from archaeologists working around the world, who knew about the archaeological record of housing in different parts of the world and got them together to design a database to capture what was available from ancient houses in societies all over the world."

They studied 55,000 floor area measurements from across North and South America, Asia, Europe and Africa, back 12,0000 years. 

via Universities of Colorado Boulder, Oxford and Florida: Kohler, Timothy A., Economic inequality is fueled by population scale, land-limited production, and settlement hierarchies across the archaeological record, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2400691122. doi.org/10.1073/pnas.2400691122

GINI Project data, as well as the analysis program developed for them, will be available open access via the Digital Archaeological Record.


Across 50 countries, female faces consistently rank higher in attractiveness than male faces
Jun 2025, phys.org

Female faces received significantly higher attractiveness ratings than male faces, an effect size that the authors describe as medium to large. That difference held across both same-sex and opposite-sex evaluations.

Female raters produced a larger disparity between ratings of male and female faces than male raters did. Male raters tended to give lower attractiveness scores overall, regardless of the gender of the face.

But - Most cultural groups showed the same female-favoring gap. Yet among Sub-Saharan African raters, no significant differences appeared. A similar absence was observed in ratings of African faces, suggesting a cultural or representational divergence not found in other ethnic categories.

via Max Planck Institute for Empirical Aesthetics: Eugen Wassiliwizky et al, The Gender Attractiveness Gap, bioRxiv (2025). DOI: 10.1101/2025.05.21.655261


'Dark' personality traits thrive in societies with corruption and inequality, global study shows
Jun 2025, phys.org

Aversive social conditions (high corruption, inequality, poverty and violence) are linked to what they call "The Dark Factor of Personality." This is the essence of aversive ("dark") personality traits such as narcissism, psychopathy, and sadism.

"The more adverse conditions in a society, the higher the level of the Dark Factor of Personality among its citizens. In societies where rules are broken without consequences and where the conditions for many citizens are bad, individuals perceive and learn that one should actually think of oneself first."

Countries such as Indonesia and Mexico or U.S. states such as Louisiana and Nevada have higher "Dark Factor" levels than countries such as Denmark and New Zealand or states such as Utah and Vermont

"Our findings substantiate that personality is not just something we are born with, but also shaped by the society we grew up and live in." (Reminds me of Sapolsky's book Determined.)

via University of Copenhagen: Ingo Zettler et al, Aversive societal conditions explain differences in "dark" personality across countries and US states, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2500830122


Beyond health: The political effects of infectious disease outbreaks
Jul 2025, phys.org

Individuals who have experienced an infectious disease outbreak show significantly less trust in the political establishment. This is especially true of their confidence in the president, parliament and ruling party of the country they live in.

To evaluate the political impact of these outbreaks, the team combined outbreak data from the Geolocated Zoonotic Disease Outbreak Dataset (GZOD) with geolocated information from the Afrobarometer surveys. The latter database records the political and social attitudes of citizens in several African states through regular surveys, and also includes information about respondents' trust in various political actors. (The Afrobarometer)

"Governments should integrate trust-preservation strategies into their epidemic response plans and make sure their decision-making is transparent, and communication is clear and consistent" (yeah good luck with that).

via University of Konstanz: Koren, Ore, Infectious disease outbreaks drive political mistrust, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2506093122


Rising temperatures linked to declining moods around the world
Aug 2025, phys.org

1.2 billion Twitter and Weibo posts from 157 countries over the span of the year 2019 were analyzed by BERT; research finds that when the temperature rises above 95 F (35 C), expressed sentiments become about 25% more negative in lower-income countries and about 8% more negative in better-off countries.

via MIT's Department of Urban Studies and Planning (DUSP) and Center for Real Estate:  Unequal Impacts of Rising Temperatures on Global Human Sentiment, One Earth (2025). DOI: 10.1016/j.oneear.2025.101422.


Using game theory to explain how institutions arise naturally to manage limited resources
Aug 2025, phys.org

Simple model predicts emergence of self-organized institutions that manage limited resources such as fisheries or irrigation water:

At each step, a person decides whether to harvest. Their decision is based on current fish stocks and how well off they and the other person are.

They have three options: cooperate with the other person by showing restraint in harvesting, punish them by over-harvesting if they feel the other person was selfish, or to act selfishly themselves.

Which category a person's response falls into depends on current fish stocks and their past history of interactions with the other person. (sounds like tit for tat)

via RIKEN Center for Brain Science: Kenji Itao et al, Self-organized institutions in evolutionary dynamical-systems games, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2500960122


Cities obey the same laws of living systems, researchers claim
Aug 2025, phys.org

The difference from the Geoffrey West Santa Fe work, is that there's apparently no efficiency in scaling up:
The scientists examined three variables: urban population (analogous to an animal's mass), carbon emissions (equivalent to the metabolic rate of a living organism) and road networks (the circulatory system).

"When properly rescaled, we found that the probability distributions of these variables follow a unique curve for all cities—large and small—implying that urban form and functions are governed by universal laws similar to those that apply to living organisms."

"Contrary to what's often been claimed, large cities aren't necessarily more sustainable than small ones—what matters is the covariation in space of population density, transport networks, and economic activities, which are all inter-related."

Because of the variation in city sizes, the authors divided each city into smaller units - like "pixels" - and employed a finite-size scaling approach.

via EPFL's Laboratory of Urban and Environmental Systems: Martin Hendrick et al, A stochastic theory of urban metabolism, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2501224122


Why some US cities thrive while others decline: New study uncovers law of economic coherence of cities
Sep 2025, phys.org

650 million U.S. census records, 6 million patents, and other historical sources covering nearly two centuries of urban development.

"We observed that, on average, the cities that make up the U.S urban system transform gradually but surely over time - from craftsmanship and manufacturing to services and engineering. Despite this, they maintain a constant level of coherence for nearly two centuries,"

"This also happened and in the same way on the West Coast, which developed later and initially in isolation from the wider U.S.. In 1850, cities such as Los Angeles and San Francisco are just emerging there with the onset of the Gold Rush," although "The transformation was massive–faster and more pronounced than on the East Coast," and "despite rapid diversification, West Coast cities' average coherence remained remarkably constant and at levels that were comparable to those of eastern US cities."

The study also shows that larger cities are consistently less coherent. A highly coherent city tends to have fewer industries that are closely related, like Detroit during its golden age of car-making, while a less coherent city, such as New York City, may span many unrelated sectors.

via Complexity Science Hub Vienna: Simone Daniotti et al, The coherence of US cities, Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2501504122

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