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September 12, 2025

Scientists detected a potential biosignature on Mars – an astrobiologist explains what these traces of life are, and how researchers figure out their source

Source: The Conversation – USA – By Amy J. Williams, Assistant Professor of Geology, University of Florida

NASA’s Perseverance rover explores Mars’ Jezero Crater. NASA/JPL-Caltech/MSSS, CC BY-NC

As the Perseverance rover traversed an ancient river valley in Mars’ Jezero Crater back in July 2024, it drilled into the surface and extracted a sample from of a unique, striped rock called Chevaya Falls. The rover’s instruments then analyzed the sample, which is called Sapphire Canyon, and surveyed the surrounding rock.

When scientists started looking into the data, they found two types of iron-rich minerals arranged on the rock in a distinctive, spotted pattern. Both these minerals are associated with life on Earth. One is found around decomposing organic matter on Earth, while the other is produced by certain microbes.

A team of researchers determined in a study published Sept. 10, 2025, that the sample contains a potential biosignature – which could suggest the red planet once hosted microbial life.

These minerals may have formed on the rock when ancient microbes used chemical reactions to produce energy. But chemical reactions not related to life can also produce these minerals under certain conditions.

To learn more, The Conversation U.S. asked Amy J. Williams, an astrobiologist at the University of Florida, about biosignature hunting on Mars and what’s so special about this Sapphire Canyon sample.

What are biosignatures?

A biosignature is any characteristic, element, molecule, substance or feature that serves as evidence for past or present life. It must be something that cannot be produced without life. Some examples include fossils, organic molecules derived from a biological process, or mineral patterns that form only through microbial activity.

An infographic showing six types of biosignatures, including organics, isotopes, minerals, chemicals, small-scale and large-scale structures — There are six types of biosignatures that scientists may find on Mars.
The Planetary Society, CC BY

A potential biosignature, which is how the Sapphire Canyon finding is described, is a substance or structure that might have a biological origin but requires more data or further study before scientists can make a conclusion about the absence or presence of life.

How do scientists determine whether something could be a biosignature on Mars?

Biosignatures come in many different flavors – chemical, physical or structural. Some are rather obvious, like a dinosaur fossil on Earth, but most are far more nuanced.

The search for ancient life on Earth partially informs the search for biosignatures on Mars. Researchers rely on subtle clues preserved in the rock record to address questions such as how long ago microbial life arose on Earth. We search for that evidence in environments such as craters and lake beds with high preservation potential, meaning those that are likely to preserve the biosignatures.

Scientists can apply these techniques to the search for life on Mars. That is why Perseverance was sent to Jezero Crater. In the ancient past, the crater hosted a river-fed lake, which on Earth would represent a habitable environment: one where life would want to live if it ever arose.

This crater was an ideal location to search for ancient life preserved in the rock record on Mars. Astrobiologists then search for chemical, textural and mineral patterns that resemble processes influenced by life back on Earth.

What makes this sample unique and interesting?

The Sapphire Canyon sample is unique because Perseverance’s PIXL and SHERLOC instruments revealed distinctive textures that were dubbed “leopard spots.” These spots are concentric reaction fronts – places where chemical and physical reactions occur – enriched in the minerals vivianite, which contains iron phosphate, and greigite, which is made of iron sulfide.

Dusty rocks on the surface of Mars, speckled with dark spots. — Chevaya Falls, a rock in the Martian Jezero Crater, is speckled with ‘leopard spots,’ which could indicate chemical reactions that may have once supported ancient life.
NASA/JPL-Caltech/MSSS

On Earth, vivianite often forms in environments with lots of decaying organic matter, while certain microbes that use sulfate for energy can produce greigite. Compounds in both these minerals are part of a chemical process called redox gradients, which refers to a series of gradual changes over physical space where chemicals can oxidize (lose electrons) or reduce (gain electrons).

One example is leaving your metal bike out in the rain. Over time, the reduced iron (Fe2+) will lose an electron and oxidize to rust (Fe3+). This process can happen nonbiologically, as exposure to water and oxygen drive the chemical changes that take your new bike to a rusty bike – I suggest not leaving it in the rain.

But some oxidation and reduction processes are so slow on their own that the only way they can occur is with living organisms that push the reactions forward. This process is how many microbes, such as bacteria, get the energy to live. Because these two minerals in the Sapphire Canyon sample both occur in redox gradients, scientists predict that microbial life, if it was ever present, could have played a role in the reactions that created these mineral signatures.

Now, scientists are looking into the explanations that wouldn’t require life to form these features on the sample.

Did scientists expect to find a sample like this?

This was a finding that we had hoped for. However, it was somewhat unexpected in this particular location. This sample came from some of the youngest sedimentary rocks the mission has investigated to date. An earlier prediction had assumed signs of ancient life would come from older Martian rock formations.

Finding these features in younger rocks widens the window of time that Mars was potentially habitable and suggests that Mars could have been habitable later in the planet’s history than scientists previously thought, and older rocks might also hold signs of life that are simply harder to detect.

NASA hosted a press conference on Sept. 10, 2025, about the mysterious sample.

What are the next steps to tell whether the sample indicates signs of past life, or whether the signature is from a nonbiological process?

The mineral associations are a potential fingerprint for those redox reactions that can occur when microbes drive the reaction forward – but abiotic processes, such as sustained high temperatures, acidic conditions and binding by organic compounds, could also explain them.

However, the Cheyava Falls rock shows no signs that it’s been exposed to the high heat or acidity usually required for greigite and vivianite to form nonbiologically. Still, the only definitive way to answer this question is to return the sample to Earth, where scientists can use advanced laboratory techniques to distinguish biological from nonbiological origins.

Amy J. Williams receives funding from NASA and is a scientist on the NASA Mars 2020 Perseverance rover mission.

– ref. Scientists detected a potential biosignature on Mars – an astrobiologist explains what these traces of life are, and how researchers figure out their source – https://theconversation.com/scientists-detected-a-potential-biosignature-on-mars-an-astrobiologist-explains-what-these-traces-of-life-are-and-how-researchers-figure-out-their-source-265157

September 12, 2025

Ten ways diabetes and dementia are linked

Source: The Conversation – UK – By Craig Beall, Associate Professor in Experimental Diabetes, University of Exeter

The link between diabetes and dementia is becoming increasingly clear. New research shows how blood sugar problems affect brain health and vice versa. Here are ten evidence-based insights into how the two conditions are related.

1. Diabetes raises the risk of dementia

People with diabetes are about 60% more likely to develop dementia than those without, and frequent episodes of low blood sugar are linked to a 50% higher chance of cognitive decline.

2. Insulin resistance affects the brain too

Insulin resistance – the major cause of type 2 diabetes – happens when cells stop responding properly to insulin. This means that too much sugar, in the form of glucose, is left in the blood, leading to complications.

It usually affects the liver and muscles, but it also affects the brain. In Alzheimer’s, this resistance may make it harder for brain cells to use glucose for energy, contributing to cognitive decline.

3. A brain sugar shortage in dementia

The brain is only 2% of our body weight, but uses about 20% of the body’s energy. In dementia, brain cells appear to lose the ability to use glucose properly.

This mix of poor use of glucose and insulin resistance is sometimes unofficially called type 3 diabetes.

4. Alzheimer’s can raise diabetes risk

People with Alzheimer’s often have higher fasting blood glucose, even if they don’t have diabetes. This is a form of pre-diabetes. Animal studies also show that Alzheimer’s-like changes in the brain raise blood glucose levels.

Also, the highest genetic risk factor for Alzheimer’s, the APOE4 genetic variant, reduces insulin sensitivity by trapping the insulin receptor inside the cell, where it cannot be switched on properly.

5. Blood vessel damage links both conditions

Diabetes damages blood vessels, causing complications in the eyes, kidneys and heart. The brain is also at risk. High or varying blood glucose levels can injure vessels in the brain, reducing blood flow and oxygen delivery.

Diabetes can also weaken the brain’s protective barrier, letting harmful substances in. This leads to inflammation. Reduced blood flow and brain inflammation are strongly linked to dementia.

6. Memantine: a dementia drug born from diabetes research

Memantine, used to treat moderate to severe Alzheimer’s symptoms, was originally developed as a diabetes medication. It didn’t succeed in controlling blood glucose, but researchers later discovered its benefits for brain function. This story shows how diabetes research may hold clues for treating brain disorders.

7. Metformin might protect the brain

Metformin, the most widely used diabetes drug, does more than just lower blood glucose. It gets in to the brain and may lower brain inflammation.

Some studies suggest that people with diabetes who take metformin are less likely to develop dementia, and those who stop taking it may see their risk increase again.

Trials are testing its effects in people without diabetes.

Bottles of metformin on a shelf. — Metformin may lower brain inflammation.
Carl DMaster/Shutterstock.com

8. Weight-loss injections may reduce plaque buildup

GLP-1 receptors agonist drugs, such as semaglutide (Ozempic, Wegovy), lower blood glucose and support weight loss. Records show that people with diabetes on these drugs have a lower dementia risk. Comparing GLP1 drugs to metformin, studies have found that they were even more effective than metformin at reducing dementia risk.

Two major trials, Evoke and Evoke Plus, are testing oral semaglutide in people with mild cognitive impairment or early mild Alzheimer’s.

9. Insulin therapy might help the brain

Since insulin resistance in the brain is a problem, researchers have tested insulin sprays given through the nose. This method delivers insulin straight to the brain while reducing effects on blood sugar.

Small studies suggest these sprays may help memory or reduce brain shrinkage, but delivery methods remain a challenge. Sprays vary in how much insulin reaches the brain, and long-term safety has not yet been proven.

10. SGLT2 inhibitors may lower dementia risk

New evidence suggests that compared to GLP-1 receptor agonists, SGLT2 inhibitors, (a type of diabetes drug) are superior at reducing dementia risk, including Alzheimer’s and vascular dementia, in people with type 2 diabetes. These tablets lower blood sugar by increasing sugar removal in urine. This study builds on early evidence suggesting they lower dementia risk by reducing inflammation in the brain.

This growing body of evidence suggests that managing diabetes protects more than the heart and kidneys, it also helps preserve brain function.

Questions remain whether diabetes drugs only reduce the diabetes-associated dementia risk or whether these drugs could also reduce risk in people without diabetes.

However, diabetes research has been very successful in creating at least 13 different classes of drugs, multiple combination therapies, giving rise to at least 50 different medicines. These reduce blood sugar, improve insulin sensitivity and reduce inflammation. A “side-effect” may be better preservation of brain health during ageing.

Craig Beall currently receives funding from Diabetes UK, Breakthrough T1D, Steve Morgan Foundation Type 1 Diabetes Grand Challenge, Medical Research Council, NC3Rs, Society for Endocrinology and British Society for Neuroendocrinology.

Natasha MacDonald receives funding from Diabetes UK.

– ref. Ten ways diabetes and dementia are linked – https://theconversation.com/ten-ways-diabetes-and-dementia-are-linked-264393

September 12, 2025

New exhibition explores history of decorative borders: from medieval manuscripts to William Morris

Source: The Conversation – UK – By Cynthia Johnston, Senior Lecturer in History of the Book, School of Advanced Study, University of London

Sir Galahad, the Quest for the Holy Grail by Arthur Hughes (1870). Works from pre-Raphaelite artists like Hughes are on display in the exhibition. Courtesy of National Museums Liverpool

The Nature of Gothic, at the Blackburn Museum and Art Gallery, explores the history of decorative borders over hundreds of years. It covers the period from the late medieval age to the Arts and Crafts Movement of the late 19th and early 20th centuries.

In the late medieval period, manuscripts that were produced in northern Europe often featured decorative borders that framed the text of both religious and secular works. These borders featured motifs from the classical world such as swirling acanthus leaves, Greek meanders and intricate patterns which interlace flowers, leaves and vines.

From the early decades of the 13th century these largely naturalistic forms, used to enhance the visual appeal of the page, began to be used more widely. They were added to the front of books and important sections within them, such as the beginnings of individual psalms or chapters of the Bible.

These naturalistic frames provided platforms tangible enough for figures, animals and grotesques to be placed upon. These characters often present an alternative reality to the verses of the psalms or Aristotle’s Libri Naturales that they decorate.

The meaning and intent of these spaces is yet to be fully understood. The battle of a miniature knight versus a fully armed snail, for example, might be interpreted as the moral fight against evil in the margins of the psalm. But the meaning of a tiny man pushing another in a wheel barrow adjacent to the beginning of Aristotle’s Libri Naturales is less clear.

The great enthusiasm for the illustrated grotesques (hybrid creatures which combine human and fantastical animal forms) in these peripheral spaces began in northern France. Texts produced by the monastic schools which emerged with the rise of scholasticism in the late 12th century often carried this type of decoration.

I have been collaborating with the Blackburn museum for over a decade, and have curated this exhibition alongside Anthea Purkis, its curator of art. This exhibition features some early examples of this technique from manuscripts held by the museum as well as examples on loan from the British Library.

In the exhibition

Decorated page from a medieval manuscript — The Bedford Psalter and Hours.
British Library Collection

Although the names of very few medieval artists whose work appeared in manuscripts are known, Blackburn Museum and the British Library both hold examples of the intricate and sophisticated work of two known illuminators.

They are Mâitre Françoise, who ran his business in Paris in the third quarter of the 15th century, and Herman Scheere – perhaps the most renowned illuminator in London in the 15th century.

From his workshop on London Bridge, Scheere produced flowing extravagant frames for the pages of his books. His book the Bedford Psalter and Hours, (loaned by the British Library and on display in the exhibition) was commissioned by the younger brother of King Henry V. This aristocratic commission demonstrates the success of Scheere’s business and the appetite for the decorated border.

Some 15th century examples from northern Europe also show the influence of Islamic art on northern European aesthetics. A 15th-century Qur’an manuscript from the John Rylands Library and Research Centre in Manchester is on display in the exhibition. muh .aqqāq script is used for Arabic primary text while the interlinear script in Persian and Eastern Turkish is in minuscule naskh script. This reflects the various communities for whom the book was intended.

The beginnings of the chapters of the Qur’an manuscript, the ṣuwwar, are surrounded by borders filled with flowing abstract forms. They’re reminiscent of, but not imitative of, the natural world. This decorative tradition would have cross pollinated with western European cultures through trade and conflict.

Examples of Persian calligraphy also demonstrate the persistence of the trend for decorative borders at this time. The Rylands’ Persian MS 10, an album completed before 1785–1786AD, features an entwined Arabic calligraphy composition formed from two slogans Tawakkaltu bi-maghfirat al-Muhaymin (I entrust myself to the forgiveness of the Guardian) in black, and Huwa al-Ghafūr Dhū-al-Raḥmah (He is the All-Forgiving Lord of Mercy) in red thuluth script. Two dark indigo blue borders bear delicate silver and gold foliage surrounding a wide margin embellished with vibrant floral flourishes.

Migration to the printed page

In 15th century Germany, Johannes Gutenberg invented the moveable-type printing press. His new technology produced a codex (an ancient manuscript text in book form) that looked like a traditional manuscript with regard to text and margins.

Rubrication – the decoration of letters in coloured inks – was added by hand to the first printed books. As the ability of printers to produce more nuanced illustrations accelerated, the decorated border survived and thrived. Indeed, its importance as part of the aesthetic in terms of how a book should look to an early modern reader drove forward innovations in technology.

The Blackburn Museum’s collection of early printed books is full of examples of the new technology of print accommodating the decorative frame.

Falling in and out of favour

The decorated frame fell out of favour in the 16th and 17th centuries. For western European readers it began to appear old fashioned. But it returned during the Industrial Revolution, thanks to the work of the Pre-Raphaelite movement.

Pre-Raphaelite artists reached back to the medieval period for their inspiration as well as artistic practice. Dante Gabriel Rossetti, William Morris, Sir Edward Coley Burne-Jones, Arthur Hughes and their associates set out to reject the values and industrial production of the 19th century. Medieval narratives found new audiences in Pre-Rapahelite art such as Arthur Hughes’ Sir Galahad, the Quest for the Holy Grail. In the subsequent Arts and Crafts Movement, books, ceramics, textiles and furniture were produced with minimal mechanical intervention. The medieval decorative frame thrived across various media.

A painting of Sleeping Beauty — Sleeping Beauty by Edward Burne Jones (circa 1885).
Manchester Art Gallery

William Morris’ hand-written copy of The Rubaiyat of Omar Khayyam provides a compelling example of the after-life of the medieval margin. On each page, the text is surrounded by a lush decorated border which is punctuated by cameos that were designed by Burne-Jones and painted by Charles Fairfax Murray.

Poem decorated with leaves and gold — The Rubaiyat of Omar Khayyam, written and decorated by William Morris.
British Library Collection

The Nature of Gothic gives visitors the opportunity to compare the work of medieval masters of decorative art with the work produced by the Pre-Raphaelites and the Arts and Crafts Movement. Contemporary artist Jamie Holman and ceramicist Nehal Aamir also contribute modern interpretations of the decorated frame.

The result is a celebration of the verdant decorative frames which twist and turn through time, illuminating art of both the past and present.

The Nature of Gothic is at the Blackburn Museum and Art Gallery from September 13 to December 13.

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With thanks to Jake Benson for the translation of Persian 10.

Cynthia Johnston is employed by The Institute of English Studies, School of Advanced Study, University of London. She receives funding from Arts Council England. This exhibit has been supported by major loans from the British Library, the John Rylands Library and Research Centre, Manchester Art Gallery and the Liverpool Museums Trust among others.

– ref. New exhibition explores history of decorative borders: from medieval manuscripts to William Morris – https://theconversation.com/new-exhibition-explores-history-of-decorative-borders-from-medieval-manuscripts-to-william-morris-261785

September 12, 2025

Regulating AI use could stop its runaway energy expansion

Source: The Conversation – UK – By Shweta Singh, Assistant Professor, Information Systems and Management, Warwick Business School, University of Warwick

Generative AI promises to help solve everything from climate change to poverty. But behind every chatbot response lies a deep environmental cost.

Current AI technology requires the use of large datacentres stationed around the world, which altogether draw enormous amounts of power and consume millions of litres of water to stay cool. By 2030, datacentres are expect to consume as much electricity as all of Japan, according to the International Energy Agency, and AI could be responsible for 3.5% of global electricity use, according to one consultancy report.

The continuous massive expansion of AI use and its rapidly growing energy demand would make it much harder for the world to cut its carbon emissions by switching fossil fuel energy sources to renewable electricity.

So, we are left with pressing questions. Can we harness the benefits of AI without accelerating environmental collapse? Can AI be made truly sustainable – and if so, how?

We are at a critical juncture. The environmental cost of AI is accelerating and largely unreported by the firms involved. What the world does next could determine whether AI innovation aligns with our climate goals or undermines them.

At one end of the policy spectrum is the path of complacency. In this scenario, tech companies continue unchecked, expanding datacentres and powering them with private nuclear microreactors, dedicated energy grids or even reviving mothballed coal plants.

Aerial view of power plants — Microsoft is set to reopen Three Mile Island nuclear power plant in Pennsylvania to power its AI services. (Photo taken in 2008. The plant has been dormant since 2019).
Dobresum / shutterstock

Some of this infrastructure may instead run on renewables, but there’s no binding requirement that AI must avoid using fossil fuels. Even if more renewables are installed to power AI, they may compete with efforts to decarbonise other energy uses. Developers may tout efficiency gains, but these are quickly swallowed by the rebound effect: the more efficient AI becomes, the more it is used.

At the other end lies a more radical possibility: a global moratorium or outright restriction on the most harmful forms of AI, akin to international bans on landmines or ozone-depleting substances.

This is politically improbable, of course. Nations are racing to dominate the AI arms race, not to pause it. A global consensus on bans is, at least for now, a mirage.

But in between complacency and prohibition lies a window – rapidly closing – for decisive, targeted action.

This could take many different forms:

1. Mandatory environmental disclosure:

AI companies could report how much energy, water and emissions are used to train and use their models. Having a benchmark helps to measure progress while improving transparency and accountability. While some countries have started to impose greater corporate sustainability reporting requirements, there is significant variation. While mandatory disclosures alone won’t reduce consumption directly, they are an essential starting point.

2. Emissions labelling for AI services:

Just as carbon emissions labels on restaurant menus or supermarket produce can guide people to lower-impact options, users could be given a chance to know the footprint of their digital choices and AI providers, like efforts to measure the carbon footprint of websites. In the US, the blue Energy Star label, one of the country’s most recognisable environmental certifications, helps customers choose energy-efficient products.

Alternatively, AI providers could also temporarily reduce functionality to account for varying levels of renewable energy available that powers them.

3. Usage-based pricing tied to impact:

Existing carbon pricing aims to ensure that heavy users should pay their environmental share. Research shows that this works best when carbon is priced across the economy for all companies, rather than just specifically targeted at individual sectors. Yet much depends on digital tech providers fully accounting for such environmental burdens in the first place.

4. Sustainability caps or “compute budgets”:

This would especially target non-essential or commercial entertainment applications. Organisations may limit their employees’ usage similar to how they restrict heavy office printing or indeed corporate travel. As companies begin to measure and manage their indirect supply chain emissions, energy and water footprints from using AI may require new business policies.

5. Water stewardship requirements in water-stressed regions:

A simple regulation here would be to ensure no AI infrastructure depletes local aquifers unchecked.

Market forces alone will not solve this. Sustainability won’t emerge from goodwill or clever efficiency tricks. We need enforceable rules.

Consumer awareness isn’t enough

Awareness does help. But expecting individuals to self-regulate in a system designed for ease-of-use is naive. “Only use AI when needed” might soon be like “Don’t print this email” a decade or two ago – well-meaning, often ignored and utterly insufficient.

Plastic figures plant trees on top of paper saying 'please don't print' — Coming soon: an AI equivalent?
awstoys / shutterstock

The world is building an AI-powered future that consumes like an industrial past. Without guardrails, we risk creating a convenience technology that accelerates environmental collapse.

Maybe AI will one day solve the problems we couldn’t, and our concerns about emissions or water will seem trivial. Or maybe we just won’t be around to worry about them.

The way we engage with AI now – blindly, cautiously, or critically – will shape whether it serves a sustainable future, or undermines it. Policymakers should treat AI as it would any other wildly profitable resource-intensive industry, with carefully thought through regulation.

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Frederik Dahlmann receives funding from National Institute for Health & Care Research (NIHR).

Shweta Singh does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Regulating AI use could stop its runaway energy expansion – https://theconversation.com/regulating-ai-use-could-stop-its-runaway-energy-expansion-258425

September 12, 2025

Bolsonaro’s conviction marks a historic moment in Brazil’s political history

Source: The Conversation – UK – By Marieke Riethof, Senior Lecturer in Latin American Politics, University of Liverpool

Four out of five members of Brazil’s supreme court have voted to convict the former president, Jair Bolsonaro, for plotting a military coup after losing the 2022 election to his left-wing rival, Luiz Inácio Lula da Silva. Bolsonaro has been sentenced to more than 27 years in prison, though his lawyers say they will appeal the decision.

Seven of Bolsonaro’s allies have also been convicted on charges related to the coup attempt. Five of these people – Walter Braga Netto, Mauro Cid, Paulo Sérgio Nogueira de Oliveira, Augusto Heleno Ribeiro and Almir Garnier Santos – come from a military or navy background. Bolsonaro’s former justice minister, Anderson Torres, and the former director of Brazil’s intelligence agency, Alexandre Ramagem, have been convicted too.

This is the first time in Brazil’s long history of political instability that a coup attempt has led to a conviction. It is also symbolically important that the only woman on the panel, Judge Carmen Lúcia, cast the deciding vote. Bolsonaro has an established track record of making denigrating comments about women.

The date of the verdict is equally important. It was delivered on September 11, which coincides with the 52nd anniversary of the 1973 Chilean military coup. This shows how far democracy in the region has come since an era when much of South America was under military rule.

Alexandre de Moraes, the supreme court judge who led the Bolsonaro trial, alluded to this in August. He said that Brazil’s 1988 constitution established the judiciary’s independence by restricting “interference by the armed forces, whether official or semi-official, in Brazilian politics”.

These constitutional guarantees mean that politicians like Bolsonaro cannot undermine democratic institutions with impunity.

The coup attempt took place on January 8 2023, less than a week after Lula was inaugurated as Bolsonaro’s successor. Echoing the attack on the US Capitol building in Washington two years earlier, hundreds of Bolsonaro supporters stormed the national congress, presidential palace and supreme court in the capital, Brasília.

They left a trail of destruction. Although the protests appeared initially to be a spontaneous act, investigations soon unearthed evidence that the event had been planned by Bolsonaro and his allies.

A history of dictatorship and threats against democracy have cast a long shadow over Brazilian politics. A right-wing military dictatorship ruled the country between 1964 and 1985. It began when the armed forces overthrew the democratically elected president, João Goulart, amid an economic crisis and fears about a turn to the left. The US government of the time supported the coup.

Brazil established a National Truth Commission in 2012, which spent two years investigating the thousands of cases of torture, extrajudicial killings, enforced disappearances and other violations that occurred during this period. However, there have been no convictions.

Under pressure from mass demonstrations and an economic crisis, the military gradually relaxed repression in the 1980s and allowed political parties to form. Brazil has been under civilian control since then. But the armed forces began to play a significant political role again during Bolsonaro’s presidency.

General Hamilton Mourão, his vice-president, served in the military during the dictatorship. And various other military figures were appointed to powerful positions in government. Bolsonaro also regularly celebrated the dictatorship and downplayed its human rights violations.

There were various examples of democratic backsliding under Bolsonaro. He, for example, questioned the legitimacy of democratic election results in 2022 – comments that saw him barred from running in elections for seven years.

Within this context, the decision to convict Bolsonaro of an attempted coup is a strong sign that Brazil’s democratic institutions have been able to withstand threats to democracy and the rule of law. It is a signal that attempts to undermine the country’s democratic institutions will not go unpunished.

Beyond Brazil’s borders

Bolsonaro’s conviction resonates beyond Brazil. During his presidency, Bolsonaro positioned Brazil as a close ideological ally to Donald Trump, who was then in his first presidential term.

Trump referred to Bolsonaro’s trial as a “witch hunt” as the court case progressed. He hit Brazil with 50% tariffs, framing them as retaliation for Bolsonaro’s prosecution. Reacting to the guilty verdict, Trump said it was “very surprising” and compared it to his own judicial struggles.

Lula has spoken out against US interference in Brazilian politics, calling the idea that “Trump can dictate rules for a sovereign country like Brazil” unacceptable.

The Brazilian foreign affairs ministry has also criticised the US secretary of state, Marco Rubio, for interfering in the country’s sovereignty and democracy. In a social media post, Rubio called the conviction “unjust” and said the US “will respond accordingly to this witch hunt”.

Looking ahead, Brazil’s next presidential elections are in 2026. Unless Bolsonaro manages to appeal his conviction and election ban, he will not be running again for the foreseeable future. Although Lula has not formally announced his candicacy he would be the front-runner.

But if there is a run-off, which would most likely be with right-wing politician and former army captain Tarcísio de Freitas, the race will probably be very close. There is a risk that the conviction will turn Bolsonaro into a martyr, which would strengthen politicians like de Freitas, who identify themselves with Bolsonaro’s politics.

Ahead of his conviction, around 40,000 Bolsonaro supporters protested in Rio de Janeiro and São Paulo. These demonstrations indicate continuing support. However, regardless of what happens next, the supreme court’s decision makes it much less likely that challenges to democracy will succeed in Brazil.

Marieke Riethof does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Bolsonaro’s conviction marks a historic moment in Brazil’s political history – https://theconversation.com/bolsonaros-conviction-marks-a-historic-moment-in-brazils-political-history-265210

September 12, 2025

Why OpenAI’s solution to AI hallucinations would kill ChatGPT tomorrow

Source: The Conversation – UK – By Wei Xing, Assistant Professor, School of Mathematical and Physical Sciences, University of Sheffield

OpenAI’s latest research paper diagnoses exactly why ChatGPT and other large language models can make things up – known in the world of artificial intelligence as “hallucination”. It also reveals why the problem may be unfixable, at least as far as consumers are concerned.

The paper provides the most rigorous mathematical explanation yet for why these models confidently state falsehoods. It demonstrates that these aren’t just an unfortunate side effect of the way that AIs are currently trained, but are mathematically inevitable.

The issue can partly be explained by mistakes in the underlying data used to train the AIs. But using mathematical analysis of how AI systems learn, the researchers prove that even with perfect training data, the problem still exists.

The way language models respond to queries – by predicting one word at a time in a sentence based on probabilities – naturally produces errors. The researchers in fact show that the total error rate for generating sentences is at least twice as high as the error rate the same AI would have on a simple yes/no question, because mistakes can accumulate over multiple predictions.

In other words, hallucination rates are fundamentally bounded by how well AI systems can distinguish valid from invalid responses. Since this classification problem is inherently difficult for many areas of knowledge, hallucinations become unavoidable.

It also turns out that the less a model sees a fact during training, the more likely it is to hallucinate when asked about it. With birthdays of notable figures, for instance, it was found that if 20% of such people’s birthdays only appear once in training data, then base models should get at least 20% of birthday queries wrong.

Sure enough, when researchers asked state-of-the-art models for the birthday of Adam Kalai, one of the paper’s authors, DeepSeek-V3 confidently provided three different incorrect dates across separate attempts: “03-07”, “15-06”, and “01-01”. The correct date is in the autumn, so none of these were even close.

The evaluation trap

More troubling is the paper’s analysis of why hallucinations persist despite extensive post-training efforts (such as providing extensive human feedback to an AI’s responses before it is released to the public). The authors examined ten major AI benchmarks, including those used by Google, OpenAI and also the top leaderboards that rank AI models. This revealed that nine benchmarks use binary grading systems that award zero points for AIs expressing uncertainty.

This creates what the authors term an “epidemic” of penalising honest responses. When an AI system says “I don’t know”, it receives the same score as giving completely wrong information. The optimal strategy under such evaluation becomes clear: always guess.

The researchers prove this mathematically. Whatever the chances of a particular answer being right, the expected score of guessing always exceeds the score of abstaining when an evaluation uses binary grading.

The solution that would break everything

OpenAI’s proposed fix is to have the AI consider its own confidence in an answer before putting it out there, and for benchmarks to score them on that basis. The AI could then be prompted, for instance: “Answer only if you are more than 75% confident, since mistakes are penalised 3 points while correct answers receive 1 point.”

The OpenAI researchers’ mathematical framework shows that under appropriate confidence thresholds, AI systems would naturally express uncertainty rather than guess. So this would lead to fewer hallucinations. The problem is what it would do to user experience.

Consider the implications if ChatGPT started saying “I don’t know” to even 30% of queries – a conservative estimate based on the paper’s analysis of factual uncertainty in training data. Users accustomed to receiving confident answers to virtually any question would likely abandon such systems rapidly.

I’ve seen this kind of problem in another area of my life. I’m involved in an air-quality monitoring project in Salt Lake City, Utah. When the system flags uncertainties around measurements during adverse weather conditions or when equipment is being calibrated, there’s less user engagement compared to displays showing confident readings – even when those confident readings prove inaccurate during validation.

The computational economics problem

It wouldn’t be difficult to reduce hallucinations using the paper’s insights. Established methods for quantifying uncertainty have existed for decades. These could be used to provide trustworthy estimates of uncertainty and guide an AI to make smarter choices.

But even if the problem of user preferences could be overcome, there’s a bigger obstacle: computational economics. Uncertainty-aware language models require significantly more computation than today’s approach, as they must evaluate multiple possible responses and estimate confidence levels. For a system processing millions of queries daily, this translates to dramatically higher operational costs.

More sophisticated approaches like active learning, where AI systems ask clarifying questions to reduce uncertainty, can improve accuracy but further multiply computational requirements. Such methods work well in specialised domains like chip design, where wrong answers cost millions of dollars and justify extensive computation. For consumer applications where users expect instant responses, the economics become prohibitive.

The calculus shifts dramatically for AI systems managing critical business operations or economic infrastructure. When AI agents handle supply chain logistics, financial trading or medical diagnostics, the cost of hallucinations far exceeds the expense of getting models to decide whether they’re too uncertain. In these domains, the paper’s proposed solutions become economically viable – even necessary. Uncertain AI agents will just have to cost more.

However, consumer applications still dominate AI development priorities. Users want systems that provide confident answers to any question. Evaluation benchmarks reward systems that guess rather than express uncertainty. Computational costs favour fast, overconfident responses over slow, uncertain ones.

Falling energy costs per token and advancing chip architectures may eventually make it more affordable to have AIs decide whether they’re certain enough to answer a question. But the relatively high amount of computation required compared to today’s guessing would remain, regardless of absolute hardware costs.

In short, the OpenAI paper inadvertently highlights an uncomfortable truth: the business incentives driving consumer AI development remain fundamentally misaligned with reducing hallucinations. Until these incentives change, hallucinations will persist.

Wei Xing does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Why OpenAI’s solution to AI hallucinations would kill ChatGPT tomorrow – https://theconversation.com/why-openais-solution-to-ai-hallucinations-would-kill-chatgpt-tomorrow-265107

September 12, 2025

Les animaux de compagnie sont-ils des gages de bonheur ? Des recherches apportent des bémols

Source: The Conversation – in French – By Christophe Gagné, PhD candidate, Psychology, Université du Québec à Montréal (UQAM)

Les gens se tournent souvent vers les animaux de compagnie pour améliorer leur humeur et trouver de la compagnie. Améliorer le bien-être et réduire la solitude font partie des raisons les plus souvent citées pour adopter un animal.

La croyance selon laquelle les animaux de compagnie apportent de nombreux bienfaits à leurs propriétaires est très répandue, mais des recherches montrent qu’avoir un animal n’est pas une panacée pour la santé psychologique.

Malgré cela, les animaux de compagnie sont souvent présentés dans les médias et sur les réseaux sociaux comme des solutions efficaces pour réduire le stress et la solitude, entretenant l’idée répandue de leurs bienfaits pour la santé. Cela peut inciter les gens à adopter des animaux de compagnie sans tenir pleinement compte des responsabilités et des exigences que cela implique, ce qui peut avoir des conséquences négatives tant pour eux-mêmes que pour leurs animaux.

En tant que psychologues sociaux étudiant les relations entre les humains et les animaux de compagnie, nous adoptons une approche plus nuancée, en examinant quand, comment et pour qui les animaux de compagnie peuvent — ou non — améliorer le bien-être.

Ce que dit la recherche

De nombreuses études ont montré que les propriétaires d’animaux de compagnie sont moins anxieux, se sentent moins seuls et moins stressés que les personnes qui n’en ont pas. Les propriétaires d’animaux domestiques se déclarent également plus satisfaits de leur vie.

Ces études retiennent souvent notre attention, car elles font écho à une croyance largement répandue : nos animaux domestiques sont bons pour nous. Ce type de recherche rassure et valide le lien profond que nous pouvons ressentir avec nos compagnons. Mais elles ne montrent qu’un seul côté de la médaille.

D’autres études n’ont trouvé aucun lien significatif entre le fait d’avoir un animal de compagnie et le bien-être humain. En fait, les personnes qui ont des animaux de compagnie ne déclarent pas nécessairement un bien-être plus élevé ni une meilleure santé mentale que celles qui n’en ont pas.

Notre étude sur le rôle des animaux de compagnie dans le bien-être humain, menée au Canada pendant la pandémie de Covid-19, a donné des résultats surprenants : elle a révélé qu’avoir un animal de compagnie était généralement associé à un bien-être et une santé mentale moindres.

L’étude portait à la fois sur des propriétaires d’animaux de compagnie et des personnes sans animaux, dans le but de comparer les deux groupes au niveau de différents indicateurs de bien-être pendant la pandémie. Les propriétaires d’animaux ont déclaré un bien-être inférieur à celui des non-propriétaires pendant cette période, notamment des niveaux de solitude plus élevés.

Ces incohérences entre les différentes études montrent que le lien entre le fait d’avoir un animal de compagnie et le bien-être n’est pas si simple. Notre étude a révélé certaines de ces nuances. Par exemple, par rapport aux propriétaires d’autres animaux de compagnie, les propriétaires de chiens ont déclaré un bien-être plus élevé.

Pour comprendre ces résultats mitigés, les chercheurs ont commencé à examiner de plus près la nature de la relation entre les propriétaires et leurs animaux de compagnie. Cette approche pourrait nous aider à mieux comprendre les facteurs qui font en sorte que la présence d’un animal de compagnie soit bénéfique au bien-être.

La qualité du lien

Tout comme nos relations avec les autres êtres humains, le lien qui nous unit à nos animaux de compagnie est complexe. De nombreux aspects de cette relation peuvent influencer les bienfaits que nous en tirons. Ce n’est pas seulement le fait d’avoir un animal de compagnie qui compte, mais aussi la façon dont nous tissons des liens avec eux et interagissons avec eux.

Par exemple, les propriétaires qui ressentent plus d’anxiété à l’idée d’être séparés de leur animal, ou qui remettent davantage en question l’affection de celui-ci, ce qui reflète un attachement inquiet à l’animal, disent également se sentir plus déprimés. Le fait de percevoir nos animaux de compagnie comme moins compréhensifs ou plus insensibles à nos besoins est également associé à des niveaux plus élevés de dépression, d’anxiété et de solitude.

À l’inverse, plus les gens ont le sentiment de partager des caractéristiques avec leurs animaux de compagnie (par exemple, la loyauté, la paresse), plus ils sont susceptibles de rapporter un bien-être plus élevé. Les animaux de compagnie sont également perçus comme vivant dans le présent, sans s’attarder sur le passé ni s’inquiéter pour l’avenir. Interagir en faisant preuve de présence attentive avec nos animaux peut nous aider à nous concentrer sur le moment présent, ce qui favorise également un plus grand bien-être.

En cultivant les aspects positifs de nos relations avec nos animaux de compagnie et en travaillant sur les aspects plus difficiles, nous pouvons atténuer le stress lié à certains des défis que représente leur prise en charge, notamment les ressources financières nécessaires ou l’anxiété que nous ressentons lorsqu’ils tombent malades.

Avoir un animal de compagnie : les défis

En réalité, avoir un animal de compagnie s’accompagne de responsabilités et de défis qui ne semblent pas être abordés aussi souvent que les avantages. Ces aspects plus difficiles de la prise en charge d’un animal de compagnie peuvent parfois être éprouvants sur le plan émotionnel et nuire au bien-être psychologique du propriétaire.

Avoir des animaux de compagnie, même si on les aime beaucoup, demande du temps, de l’énergie et des ressources financières. Pour certains, cette responsabilité peut représenter une source supplémentaire de stress. Dans notre étude, le fait d’avoir un animal de compagnie était associé, durant la pandémie de Covid-19, à un bien-être moindre chez les femmes et chez les personnes ayant deux enfants ou plus à la maison, des groupes déjà confrontés à des exigences accrues liées aux enfants et aux tâches ménagères.

Déjà des milliers d’abonnés à l’infolettre de La Conversation. Et vous ? Abonnez-vous gratuitement à notre infolettre pour mieux comprendre les grands enjeux contemporains.

De même, avoir un animal de compagnie était associée à un bien-être moindre chez les personnes sans emploi ou ayant un emploi moins stable (par exemple, les étudiants, les personnes au foyer). Des ressources financières limitées pouvaient rendre plus difficile la prise en charge de l’animal.

De même, devoir s’occuper d’un animal malade peut être éprouvant sur le plan émotionnel pour les propriétaires. Les personnes qui s’occupent de chiens atteints d’une maladie chronique déclarent se sentir désespérées et impuissantes, en particulier lorsqu’elles ne peuvent pas soulager la souffrance de leur animal.

D’autres facteurs, tels que les problèmes de comportement d’un animal et le deuil vécu après la perte d’un animal de compagnie, peuvent également être difficiles à vivre pour les propriétaires. Pour ceux qui envisagent d’adopter un animal, il est important de tenir compte de ces réalités afin de prendre une décision éclairée.

Répondre aux besoins de notre animal

Il y a de nombreux facteurs importants à prendre en compte avant d’accueillir un nouvel animal de compagnie dans notre maison. Avant tout, nous devons nous assurer que nous avons le temps, l’énergie et les ressources nécessaires pour répondre à ses besoins.

Choisir un animal de compagnie avec soin, en fonction de ce que nous pouvons réellement lui offrir et sur la base d’informations fiables concernant ses caractéristiques et ses besoins, nous donne les meilleures chances d’avoir une relation positive et épanouie.

Répondre aux besoins de nos animaux de compagnie peut également améliorer notre propre bien-être en tant que propriétaires, démontrant ainsi le potentiel des relations interespèces mutuellement bénéfiques. Mais lorsque ces besoins ne sont pas satisfaits, les animaux de compagnie et leurs propriétaires peuvent finir par se sentir stressés et anxieux.

Lorsque l’on envisage d’adopter un animal de compagnie, il est important de se poser la question suivante : pourquoi voulons-nous un animal de compagnie ? Si l’idée est d’améliorer notre bien-être psychologique, nos recherches suggèrent qu’il faudrait peut-être y réfléchir à deux fois.

Catherine Amiot fait partie du conseil d’administration émergent de la PHAIR Society, une société savante qui vise à promouvoir la recherche sur les relations intergroupes entre les humains et les animaux. Elle a reçu du financement du Conseil de recherches en sciences humaines du Canada (CRSH) et du Fonds de recherche du Québec – Santé (FRQS) pour les recherches menées dans son laboratoire et présentées dans cet article.

Christophe Gagné ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’a déclaré aucune autre affiliation que son organisme de recherche.

– ref. Les animaux de compagnie sont-ils des gages de bonheur ? Des recherches apportent des bémols – https://theconversation.com/les-animaux-de-compagnie-sont-ils-des-gages-de-bonheur-des-recherches-apportent-des-bemols-263144

September 12, 2025

Millennial pink, Gen-Z Yellow, Brat Green… Décris-moi tes couleurs préférées, je devinerai ta génération

Source: The Conversation – France (in French) – By Sabine Ruaud, Professeur de marketing, EDHEC Business School

Chaque époque a ses couleurs emblématiques : les pastels rassurants des boomers, le rose poudré des milléniaux, le jaune éclatant et le vert tape-à-l’œil de la Gen Z. Reflets d’émotions collectives et de tendances sociétales, ces teintes en disent souvent plus long que de simples effets de mode.

Chaque génération semble s’approprier certaines teintes, mais il serait réducteur d’y voir une donnée biologique ou universelle. Si la couleur est l’effet visuel résultant de la composition spectrale de la lumière qui est envoyée, transmise ou réfléchie par des objets, la façon dont on l’envisage est avant tout une construction sociale et culturelle qui reflète les mœurs, les évolutions idéologiques et les influences médiatiques d’une époque.

En effet, comme l’a commenté Michel Pastoureau, ce n’est pas la nature qui fait les couleurs ni même l’œil ou le cerveau, mais la société qui leur attribue des significations variables selon les époques. Elles deviennent ainsi des témoins privilégiés des mutations de chaque décennie.

Dans un chapitre récemment publié, « La couleur, marqueur créatif générationnel ? », nous nous sommes intéressés à la façon dont les générations successives se caractérisent par un ensemble de valeurs, de croyances et de comportements qui se manifestent visuellement, notamment à travers des couleurs qui leur sont propres.

Ainsi, la segmentation par générations – boomers, générations X, Y, Z, Alpha – permet d’observer des affinités chromatiques qui ne relèvent pas seulement du goût individuel, mais d’un rapport collectif au temps, aux aspirations et aux codes esthétiques dominants.

À chaque génération, son code couleur

Les boomers (nés entre la fin de la Seconde Guerre mondiale et le milieu des années 1960, ndlr– et la génération X (née entre 1965 et 1980) se caractérisent par une préférence pour des palettes dites traditionnelles, dominées par des tons neutres et pastels auxquels s’ajoutent, à partir des années 1970, des couleurs inspirées de la nature comme les verts, les bruns et les rouges terreux.

La génération Y, ou les millennials (en français, les milléniaux ; nés entre 1980 et le milieu des années 1990, ndlr), a quant à elle été marquée par l’émergence d’un rose emblématique, le « millennial Pink ». Plus qu’une simple teinte, ce rose pâle s’est imposé dans les années 2010 comme un symbole de légèreté, d’optimisme et surtout de remise en question des codes de genre.

Pour la génération Z (née entre 1995 et 2010), c’est d’abord un jaune vif, le « Gen-Z Yellow », qui s’est imposé, au tournant de 2018, en contraste avec le rose singulier de ses aînés. Rapidement, le violet est venu compléter cette palette, couleur historiquement liée au pouvoir, à la créativité et aux luttes féministes et, désormais, associée à l’expression de soi et à l’inclusivité. Plus récemment, le vert a gagné en importance : d’un côté, comme couleur associée aux enjeux écologiques, fréquemment mobilisée et récupérée dans le champ politique ; de l’autre, comme tendance numérique et provocante, le « Brat Green », popularisé, en 2024, par la chanteuse britannique Charli XCX.

La génération Alpha, encore en formation, oscille pour sa part entre un attrait pour les tons naturels et réconfortants et une exposition précoce aux couleurs franches et artificielles de l’univers digital.

S’ancrer dans son époque

Si ces repères générationnels sont séduisants, il est essentiel de ne pas les figer. Les couleurs ne se laissent pas réduire à des étiquettes fixes : elles vivent, elles circulent, elles se réinventent. Elles reviennent parfois de manière cyclique, à l’image de la mode, et se rechargent de nouvelles significations. C’est ce qui rend la couleur si puissante dans la communication. Elle permet d’ancrer une marque dans son époque tout en laissant place à la réinterprétation.

L’actualité chromatique de 2024–2025 en témoigne. À côté du vert néon insolent de l’album à succès Brat, de Charli XCX, l’entreprise Pantone a choisi « Mocha Mousse » comme couleur de l’année 2025, un brun cosy, gourmand et enveloppant qui traduit le besoin collectif de réassurance et d’ancrage. Le contraste entre ces deux signaux, l’un pop et ironique, l’autre discret et rassurant, illustre parfaitement la tension contemporaine entre exubérance et quête de stabilité.

Les recherches en marketing montrent, par ailleurs, que l’impact des couleurs ne réside pas seulement dans la teinte elle-même, mais aussi dans la manière dont elle est nommée.

Le « color naming » des marques

Le « color naming » a un effet direct sur la préférence et l’intention d’achat : un nom de produit évocateur, poétique ou humoristique génère davantage d’engagement qu’un terme générique. Ce phénomène, encore peu documenté, rappelle aux marques que les mots façonnent autant que les couleurs la perception des produits. L’excès d’humour peut toutefois brouiller la mémorisation de la marque, d’où la nécessité d’un dosage subtil

Pour les entreprises, l’enjeu est donc double. Il s’agit, d’une part, de comprendre les codes chromatiques ponctuels qui circulent dans une génération donnée, afin de parler un langage immédiatement perceptible, et, d’autre part, de créer un système de couleurs qui reste cohérent et durable dans le temps.

Parler de « couleurs de génération » reste un outil utile de décryptage, mais uniquement si l’on accepte sa plasticité. Pour chaque génération, la couleur est une passeuse de messages, un support de signes tacites ou exprimés de toutes sortes, un témoin clé dont les nuances suscitent des émotions, véhiculent des significations et procurent des expériences variées.

Les auteurs ne travaillent pas, ne conseillent pas, ne possèdent pas de parts, ne reçoivent pas de fonds d’une organisation qui pourrait tirer profit de cet article, et n’ont déclaré aucune autre affiliation que leur organisme de recherche.

– ref. Millennial pink, Gen-Z Yellow, Brat Green… Décris-moi tes couleurs préférées, je devinerai ta génération – https://theconversation.com/millennial-pink-gen-z-yellow-brat-green-decris-moi-tes-couleurs-preferees-je-devinerai-ta-generation-260366

September 12, 2025

Fewer international students are coming to the US, costing universities and communities that benefit from these visitors

Source: The Conversation – USA (2) – By Tara Sonenshine, Edward R. Murrow Professor of Practice in Public Diplomacy, Tufts University

The international student population is expected to experience a dive in the fall of 2025. iStock/Getty Images Plus

American college campuses from Tucson to Tallahassee are buzzing with the familiar routine of students getting settled in classes and dorms.

One new trend, though, is emerging.

An estimated 30% to 40% fewer international students are expected on American college campuses in the fall of 2025, compared with trends in the 2024-2025 academic year, according to according to NAFSA: Association of International Educators – a nonprofit that focuses on international education – and JB International, a for-profit educational technology firm.

In total, an estimated 150,000 fewer international students were expected to arrive this fall, due to new visa restrictions and visa appointments being canceled at U.S. embassies and consulates in many countries, such as India, China, Nigeria and Japan. NAFSA and JB International are expected to release updated data on international student enrollment in November 2025.

There were over 1.1 million international students – more than half of whom were from China or India – on American college campuses in the 2023-2024 academic year, according to the Institute for International Education, which monitors foreign student programs and shares the most comprehensive available recent data.

This sharp drop in international students could cost the U.S. economy US$7 billion in the 2025-26 school year, according to estimates from NAFSA.

For every three international students in the U.S., one new American job is created or supported by the average $35,000 these students spend in their local communities on housing, food and transportation, and other costs.

As a senior fellow at the Fletcher School of Law and Diplomacy at Tufts University and a former undersecretary of state for public diplomacy in the Obama administration, I oversaw many of the student exchange programs involving multiple countries around the globe. I foresee a major economic crisis over international students that could last for years.

Two young Chinese women with dark hair hold red flags with yellow stars on them. One of the women wears a light blue graduation robe and smiles. — A Chinese Columbia University student and a friend attend graduation in May 2019.
Mark Lennihan/Associated Press

A growing trend, quickly reversed

International students began coming to the U.S. in the early 20th century, when philanthropists like the Carnegie, Rockefeller and Mott families sought out scholars from the U.S. to go overseas. These philanthropists helped create international fellowships and grants that later on would often be funded by the U.S. government – like the Fulbright program, which gives money to American students to spend time and research abroad.

By 1919, nonprofits like the Institute for International Education
were serving as mediators between foreign students and American universities.

International student enrollment in the U.S. has steadily risen since the end of World War II, coinciding with an emerging world that became easier and cheaper to travel across. While 26,000 foreign students came to the U.S. in the 1949–1950 school year, that number had ballooned to 286,343 three decades later.

In the 1990s, there were more than 400,000 international students attending school in the U.S. each year. That number continued to climb and surpassed 500,000 in the early 2000s.

International student enrollment in the U.S. first topped more than 1 million in the 2015-2016 school year.

While international students made up just 1% of the 2.4 million university and college students in the U.S. in 1949-50, they were about 6% of the total 18.9 million students in the U.S. in 2023-24, according to the Migration Institute, a nonpartisan research organization.

This percentage is relatively small, however, compared with the international student representation in other countries.

International students represented 38% of overall Canadian university enrollment, made up 31% of all university students in Australia and 27% of all students in the United Kingdom during the 2024-2025 school year.

Trump’s warnings to international students

Within the first 90 days of his return to office, President Donald Trump invoked the 1952 Immigration and Nationality Act, which gives the secretary of state the authority to expel foreign students whose behavior could pose a threat to U.S. foreign policy interests.

The administration has since revoked the visas of 6,000 foreign students, the State Department reported in August 2025.

There have also been several high-profile arrests of international students, including Rumeysa Ozturk, a Turkish student at Tufts University. Immigration and Customs Enforcement officials arrested Ozturk in March 2025 shortly after the administration revoked her visa. Her arrest came one year after she co-wrote an opinion piece calling for Tufts to recognize a genocide in the Gaza Strip and to divest from all companies with ties to Israel.

Secretary of State Marco Rubio defended Ozturk’s arrest, saying in March that the government will not give visas to people who come to the U.S. intending to do “things like vandalizing universities, harassing students, taking over buildings, creating a ruckus.”

A federal judge ruled in May that there was no evidence showing Ozturk posed a credible threat to the U.S. She was then released from an immigration detention facility.

But her arrest coincided with the arrest of other international students in high-profile cases, like Mahmoud Khalil, a Columbia graduate student and U.S. permanent resident who was arrested after he participated in Palestinian rights protests on campus. These arrests all sent a message to foreign students: It is not as safe as it once was to come to the U.S.

The administration has announced other changes that will make it more difficult for foreign students to spend time in the U.S. – like a 2025 travel ban that prohibits or restricts the entry of people from 19 countries, mostly in the Middle East and Africa.

The administration also announced in August that it plans to cap the length of time foreign students can stay in the U.S. to four years. Currently, foreign students have a 60-day grace period to stay in the U.S. following graduation, before they must secure a work visa or another kind of authorization to legally stay in the country.

A group of young people wear black robes and black graduation hats and walk together. Some of the people hold globes. — Harvard graduates exit the university’s commencement ceremony holding globes in May 2025.
Sydney Roth/Anadolu via Getty Images

A simple math equation

New York University, Northeastern University in Boston and Columbia University hosted the largest number of international students in 2023-2024. But international students are not concentrated in just major, liberal cities.

Arizona State University hosted the fourth-highest number of international students that school year, and Purdue University in Indiana and the University of North Texas also are among the 10 schools that host the total most international students.

All of these schools – and others, like Kansas City colleges and universities, which are now welcoming far fewer international students than they planned to in the spring because some of the students could not get visas – will feel the financial effects of turning international students away from the U.S.

Doing the math, I believe that a solid argument can be made for increasing the numbers of foreign students coming to the U.S., not cutting back.

Tara Sonenshine does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Fewer international students are coming to the US, costing universities and communities that benefit from these visitors – https://theconversation.com/fewer-international-students-are-coming-to-the-us-costing-universities-and-communities-that-benefit-from-these-visitors-264012

September 12, 2025

Beauty sleep isn’t a myth – a sleep medicine expert explains how rest keeps your skin healthy and youthful

Source: The Conversation – USA (3) – By Joanna Fong-Isariyawongse, Associate Professor of Neurology, University of Pittsburgh

Getting enough sleep is one of the most accessible and powerful ways to maintain healthy skin. TatyanaGl/iStock via Getty Images

Have you ever woken up after a night of poor sleep, glanced in the mirror and thought, “I look tired?”

You’re not imagining it.

I am a neurologist who specializes in sleep medicine. And though “beauty sleep” may sound like a fairy tale, a growing body of research confirms that sleep directly shapes how our skin looks, how youthful it appears and even how attractive others perceive us to be.

What happens during sleep

Sleep is not just down time. Your body moves through distinct stages that serve different restorative functions. Deep, slow-wave sleep is the primary stage during which the body prioritizes tissue repair, muscle recovery and collagen production.

Growth hormone is released during this sleep stage, with most daily secretion occurring in the early part of the night. This hormone drives the body’s repair and rebuilding processes, helping to heal tissues, restore muscles and boost the production of collagen, the protein that keeps skin firm and elastic.

Slow-wave sleep also creates a unique hormonal environment that benefits the skin. Cortisol, the body’s main stress hormone, falls to its lowest point during this stage. Lower cortisol protects collagen, reduces inflammation and supports the skin barrier. At the same time, higher levels of growth hormone and prolactin, a hormone that helps regulate the immune system and cell growth, enhance immune function and tissue repair, helping skin recover from daily stressors.

The skin–sleep connection

The skin is your body’s largest organ, and it works hard while you sleep. Adequate sleep promotes hydration and barrier function, helping your skin maintain moisture and resist irritation. In contrast, sleep deprivation increases water loss through the skin, leaving it drier and more vulnerable to damage and visible signs of aging.

Sleep also plays a role in acne, a common skin condition that affects people of all ages. Poor sleep can raise inflammation and stress hormones such as cortisol, both of which may worsen breakouts. Consistent, restorative sleep, on the other hand, supports your skin’s ability to regulate oil production and recover from irritation.

Collagen repair and elasticity also depend heavily on adequate rest. In one study, short-term sleep restriction, defined as just three hours of sleep per night for two nights in a row, reduced skin elasticity and made wrinkles more noticeable.

Chronic sleep deficiency, also known in sleep medicine as insufficient sleep syndrome, refers to getting fewer than seven hours of sleep per night for at least three months, accompanied by daytime fatigue or impaired functioning. This state disrupts collagen production, weakens the skin barrier and fuels low-grade inflammation that undermines healing.

Studies show that the hormonal disruptions that occur with sleep loss elevate cortisol and accelerate oxidative stress, an imbalance between cell-damaging molecules and the body’s defenses, while impairing the very processes that keep skin resilient. Over time, these changes accelerate biological aging and leave the body less resilient to daily stressors.

Serums, sunscreens and moisturizers may be good for your skin, but they can’t make up for poor sleep habits.

Your face tells the story

Sleep loss does not only affect how skin functions. It also changes how the face appears to others. Controlled studies show that even after a few nights of reduced sleep, others consistently rated them as less attractive, less healthy and more fatigued. Common cues include paler skin, darker under-eye circles, red or swollen eyes, drooping eyelids and downturned mouth corners.

These signals are subtle but socially significant. Observers are less inclined to interact with or approach someone who looks sleep-deprived. Sleep also affects empathy and aesthetic perception, meaning that people who are well rested not only view others more positively but are also, in turn, viewed more positively by others. This reciprocal effect may help explain why job interviewers, dates, or even friends tend to respond more favorably to a well-rested face.

Sleep even influences how we perceive ourselves. People with poor sleep often report lower satisfaction with their own appearance.

Supporting your health

Prioritizing sleep is a powerful and accessible way to support appearance and overall health. So the next time you consider trading sleep for a few extra hours of work or entertainment, remember that your skin, your health and even your social presence will benefit from those hours of rest.

Joanna Fong-Isariyawongse does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

– ref. Beauty sleep isn’t a myth – a sleep medicine expert explains how rest keeps your skin healthy and youthful – https://theconversation.com/beauty-sleep-isnt-a-myth-a-sleep-medicine-expert-explains-how-rest-keeps-your-skin-healthy-and-youthful-259363