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In 2025, five people saw a colour called 'olo', a blue-green more saturated than anything in nature. Berkeley researchers produced it by aiming lasers at single cells in the retina so that only the eye's 'green' cone cells responded, something natural light cannot do.

Science Advances, 2025

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The eye sees colour with three kinds of cone cell, sensitive to short, medium and long wavelengths and loosely called blue, green and red. Their sensitivities overlap, so any natural light that reaches the medium, or 'M', cones also stimulates their neighbours. The team, led by Ren Ng and Austin Roorda at the University of California, Berkeley, mapped individual cones in a small patch of each participant's retina, tracked the eye as it moved and sent tiny laser pulses to M cones alone. Their paper appeared in Science Advances in April 2025. The name comes from 0-1-0: only the middle cone type switched on. The closest a screen can show is a strong teal, but participants described olo as far more saturated.

Türkçe oku
2025'te beş kişi, “olo” adı verilen ve doğadaki hiçbir renkte görülmeyen canlılıkta bir mavi-yeşil gördü. Berkeley'deki araştırmacılar bu rengi, retinadaki hücrelere tek tek lazer tutup yalnızca gözün “yeşil” koni hücrelerini uyararak elde etti. Doğal ışık bunu yapamaz.
Science Advances, 2025

Göz renkleri üç tür koni hücresiyle görür. Bunlar kısa, orta ve uzun dalga boylarına duyarlıdır ve kabaca mavi, yeşil ve kırmızı diye anılır. Duyarlılıkları birbiriyle örtüştüğü için doğadaki ışık orta dalga boyuna duyarlı “M” konilerini uyardığında komşu konileri de uyarır. California Üniversitesi Berkeley'den Ren Ng ve Austin Roorda'nın yönettiği ekip, her katılımcının retinasında küçük bir bölgedeki konileri tek tek haritaladı, gözün hareketini izledi ve yalnızca M konilerine minik lazer atımları gönderdi. Çalışma Nisan 2025'te Science Advances dergisinde yayımlandı. Renk adını 0-1-0 dizisinden alır: Yalnızca ortadaki koni türü uyarılmıştır. Bir ekranın gösterebileceği en yakın renk koyu bir turkuazdır, ama katılımcılar “olo”nun çok daha canlı olduğunu söyledi.

Sources and further reading

Background reading: Cone cell
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The 'Mozart effect', the popular idea that listening to Mozart makes you cleverer, grew from a 1993 study of just 36 college students. After hearing a Mozart sonata, their scores on a spatial-reasoning task rose for only 10 to 15 minutes; later reviews found no lasting boost to intelligence.

Frances Rauscher, Gordon Shaw and Catherine Ky published the study in the journal Nature. Students listened to ten minutes of Mozart's Sonata for Two Pianos in D major, a relaxation recording or silence, then did paper-folding-and-cutting puzzles from the Stanford-Binet intelligence test. The Mozart group did better, but only briefly, and the study involved no babies, no children and no measure of general intelligence. Publicity turned it into a promise that classical music makes children smarter: in 1998 the governor of Georgia, Zell Miller, proposed $105,000 a year to give every newborn in the state a classical recording. Later analyses found at most small, short-lived effects, most likely because lively music lifts mood and alertness.

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Deliberately smiling can make people feel slightly happier. In 2022 a study of nearly 4,000 people in 19 countries found that posing a smile, or copying a smiling face, raised reported happiness a little; a subtler method, holding a pen between the teeth, gave less clear results.

The idea that the face can feed back into feelings, called the facial feedback hypothesis, goes back to Charles Darwin and William James. In a famous 1988 experiment, Fritz Strack and colleagues had people hold a pen in their teeth, which forces a smile, or between their lips, which prevents one, and those in the first group rated cartoons as funnier. In 2016, seventeen laboratories repeated that experiment exactly and found no effect. A 2019 review of 138 studies concluded that the effect is real but small and varies from study to study. The 2022 Many Smiles Collaboration, led by Nicholas Coles and designed jointly by supporters and sceptics of the idea, found that deliberate smiling could both strengthen and start feelings of happiness, while the pen method remained inconclusive.

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In a cave in Jujuy, northern Argentina, archaeologists found two pipes carved from puma bone, with seeds of cebil, a tree whose seeds are psychoactive, lying beside them. Chemical traces inside the pipes point to plant smoking more than 4,000 years ago, among the oldest evidence of such use in South America.

Cebil, Anadenanthera colubrina, is a South American tree whose seeds contain tryptamines, compounds that strongly alter perception; further north in the Andes it is called vilca. The pipes come from Inca Cueva 7, a small rock shelter near the Humahuaca valley at the edge of the high Andean plateau, where seeds of cebil and of mesquite lay in the same layer. Radiocarbon measurements, which gauge how much of the carbon-14 in once-living material has decayed, give ages of about 4,000 years, roughly 2100 BC. The residue shows that a tryptamine-bearing plant was smoked, but it cannot prove exactly which one. Cebil use continued in the region for thousands of years: Wichí healers in northern Argentina still used its seeds, which they call hatáj, in the 1990s.

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Your gut and brain communicate through nerves, hormones, immune signals and microbes, which is why stress and digestion can affect each other.

Scientists call this link the gut–brain axis. The gut has its own network of about 500 million nerve cells, the enteric nervous system, sometimes called the “second brain”, which can run digestion largely by itself. It is connected to the brain mainly through the vagus nerve, a long nerve running from the brainstem down to the abdomen, and most of its fibres carry messages upwards, from the gut to the brain. More than 90 per cent of the body's serotonin, a chemical messenger, is found in the gut. Gut bacteria play a part too: in a 2004 Japanese study, mice raised entirely free of germs overreacted to stress. Stress can speed up or slow down the gut, one reason it often worsens irritable bowel syndrome, a common gut disorder. Most research on the microbes' role has been in animals, and human evidence is still limited.

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A placebo is a dummy treatment, such as a sugar pill. In pain studies, placebos can reduce the pain people report and also dampen activity in the brain areas that process pain, even though they contain no active drug.

The word placebo is Latin for “I shall please”. One of the first clues that the effect is physical came in 1978, when Jon Levine and colleagues studied patients recovering from wisdom tooth removal. They gave them a placebo and naloxone, a drug that blocks the effect of endorphins, the body's own painkilling chemicals. In patients who had responded to the placebo, naloxone increased the pain, which suggested that the placebo relief came from endorphins. In 2004 Tor Wager and colleagues used brain scans to show that a placebo painkiller reduced activity in pain-processing regions during a painful stimulus. Expectation works the other way too: in the nocebo effect, from the Latin for “I shall harm”, expecting harm makes symptoms worse. None of this means the pain was imaginary, or that placebos can replace effective treatment.

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