A Model That Learns Words Like a Toddler, a Fault That Locked Again and the Ice Age's Slow Lurch

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A good deal of this week's science is about time. How long it takes a baby to find words, a fault to grip again, and an ocean to change its mind.

Start in fifteen American homes, where cameras and microphones ran twelve to fourteen hours a day through the first years of a child's life. Princeton's First 1,000 Days project is one of the densest records ever made of what small children actually hear.

A team led by Hadas Raviv and Uri Hasson has used it to ask how much of language can be learned from everyday experience alone. Writing in Science, they gave each of eight children their own AI model and fed it that child's household speech in order, one day at a time. No text, no dictionary, nothing marking where one word ends and the next begins. Just the sound of ordinary family life.

At first the model kept almost nothing from one day to the next. What changed that was a kind of nightly revision. At the end of each simulated day, the model went back over a limited sample of recent speech, mostly from the last few days. The idea was inspired by the way sleeping brains seem to replay experience, though the team is clear it isn't modelling sleep itself.

With replay switched on, things started to happen. The model sorted the stream of sound into units matching nearly all the speech sounds of English, then began picking out words that kept coming back. By its simulated second birthday, the model trained in one child's home had a vocabulary in the thousands. Models for the other seven homes did the same, with identical settings.

Real children don't keep identical schedules, though. Some of these kids reached a big vocabulary nearly a year before others. The models could match each child's own timeline by adjusting just a few internal dials, mainly how much they replayed each night and how quickly they learned.

These models aren't children. They can't point at the cat or watch a parent's face, and they don't know what a single word means. But the study suggests ordinary household chatter carries enough structure to find a language's sounds and words, given a learner that goes back over what it heard.

To Japan, where a fault has quietly got its grip back. In 2011 the magnitude nine Tohoku earthquake ruptured the boundary where the Pacific Plate dives beneath northeastern Japan, and parts of it slipped more than ten metres. Afterwards, the boundary kept creeping slowly, which geologists call afterslip, releasing strain rather than storing it.

The question has been when it would lock again and start loading up for the next one. That means measuring the seabed, where GPS doesn't reach. So researchers fix a position at the surface, from a ship or an uncrewed, surfboard-like robot called a Wave Glider, then use sound pulses to locate instruments sitting on the sea floor. Using twenty-six of those seafloor sites over fourteen years, a team led from Tohoku University, with colleagues in Canada, reports in Science that the shallow afterslip had essentially stopped by around 2021. Some stations off Fukushima and Ibaraki literally reversed direction, from drifting out to sea to being dragged back toward land.

The shallow boundary is now about as locked as it was before 2011, and the patches that slipped most began storing energy again soon after the quake. Deeper down, the mantle is still slowly relaxing. Giant earthquakes here are thought to come every five hundred to nine hundred years on average, though shorter gaps can't be ruled out. Either way, the clock is running again.

Next, a revision to a famous picture of sudden climate change. During the last ice age, Greenland repeatedly lurched into warm spells, with temperatures in the far north jumping somewhere between five and sixteen degrees, and ice cores suggested each jump took only decades. Those events are tied to a speeding up of the Atlantic's great overturning circulation, the current system that carries warm water north.

A team led by Xiyu Dong at Xi'an Jiaotong University read stalagmites from caves in India and China, which grow in yearly layers rather like tree rings. Their record, also in Science, says the circulation shifts took more than a century each, around a hundred and eighty years on average. Their climate models suggest Greenland's ice caught the first, fast step, sea ice retreating in the northeastern Atlantic and the winds rearranging, while the ocean current itself strengthened more gradually. This is the natural past, not today's warming, but the authors argue that any talk of an Atlantic tipping point should come with a timescale.

Finally, the cave on the Indonesian island of Flores where the small human relative Homo floresiensis was found has a new bird. A single leg bone, dug up in 2009 and filed as simply "bird", has been named Megapodius rokusi by Hanneke Meijer at the University Museum of Bergen. Megapodes are chicken-like birds that don't sit on their eggs at all. They bury them in mounds of soil and rotting leaves and let the heat do the incubating. The species living on Flores today weighs around a kilo. This one, somewhere between a hundred and twenty and a hundred and ninety thousand years old, weighed nearly four. Whether it could fly, nobody knows. Nobody's found its wings.

That's us for today. If there's a toddler in your life, keep talking. Somebody's replaying all of it tonight.