Any parent trying to hustle a school-bound kid out the door in the morning knows that her child’s skull possesses a strange and powerful form of black magic: It can repel parents’ voices. Important messages like “find your shoes” bounce off the impenetrable fortress and drift unheeded to the floor.

But when this perplexing force field is off, it turns out that mothers’ voices actually have profound effects on kids. Children’s brains practically buzz when they hear their moms’ voices, scientists report in the May 31 Proceedings of the National Academy of Sciences. (Fun and not surprising side note: Babies’ voices get into moms’ brains, too.)

The parts of kids’ brains that handle emotions, face recognition and reward were prodded into action by mothers’ voices, brain scans of 24 children ages 7 to 12 revealed. And words were not required to get this big reaction. In the study, children listened to nonsense words said by either their mother or one of two unfamiliar women. Even when the words were fake, mothers’ voices still prompted lots of neural action.

The study was done in older kids, but children are known to tune into their mothers’ voices early. Really early, in fact. One study found that fetuses’ heart rates change when they hear their moms read a story. For a fetus crammed into a dark, muffled cabin, voices may take on outsized importance.

And voices carry particularly powerful messages throughout childhood. “A tremendous amount of emotional information is conveyed to children through auditory channels,” says University of Wisconsin-Madison child psychologist Seth Pollak. And, he points out, kids are small. “Kids’ faces are down around our knees. And children who are crawling are looking at the ground,” he says. This obvious point means that facial expressions and other visual signals might not pack as much punch as a voice.

Of course, voices other than those belonging to moms are also important. Pollak says that voices of fathers — or any other caregiver who spends lots of time around a child — probably affect children’s brains in a similar way. It’s just that those studies haven’t been done yet.

The results of the latest brain scan study make a lot of sense, says Pollak. Some of the brain regions activated are those involved in feeling good. “A caregiver’s voice is actually rewarding. It activates the systems that make us feel calm,” he says.
And the new study might help explain some of Pollak’s earlier results. He and his colleagues stressed out 68 girls, who happened to be the same ages as those in the brain scanning study, by making them do math and word problems in front of three unsmiling adult strangers — a terrifying prospect for most kids. (And adults.) After their ordeal, the girls either talked to their moms in person, on the phone or by instant messenger.

Compared with the instant messenger typers, the girls who saw their moms in person or talked to them on the phone were more soothed, showing lower levels of stress hormones. That finding, published in 2012 in Evolution and Human Behavior, suggests that to a kid, there’s something especially calming about hearing her own mother’s voice.

And now, by showing the widespread reaction to a mother’s voice, the brain data back that up. “It all kind of hangs together in a way that I think is very intuitive,” Pollak says. In other words, a mother’s voice is powerful, perhaps even strong enough to overcome a force field.

Thanks to modern laser technology, Southeast Asia’s Khmer Empire is rising from forest floors for the first time in centuries.

New findings show the remarkable extent to which Khmer people built cities and transformed landscapes from at least the fifth to the 15th century, and perhaps for several hundred years after that, says archaeologist Damian Evans of Cambodia’s Siem Reap Center. Laser mapping in 2015 of about 1,910 square kilometers of largely forested land in northern Cambodia indicates that gridded city streets and extensive canals emerged surprisingly early, by around A.D. 500, Evans reports June 13 in the Journal of Archaeological Science. Researchers have generally assumed that large-scale urban development began later at Greater Angkor, capital of the Khmer Empire from the ninth to 15th centuries (SN: 5/14/16, p. 22).
A helicopter carrying light detection and ranging equipment, lidar for short, flew sorties over seven Khmer sites in the vicinity of Greater Angkor. Lidar’s laser pulses gathered data on the contours of jungle- and vegetation-covered land. Lidar maps revealed city blocks, canals and other remnants of past settlements.
Mysterious ground features previously identified by lidar surveys at Angkor Wat temple in Greater Angkor also turned up at several sites, some located as many as 100 kilometers from Greater Angkor. Those sites include the eighth to ninth century city of Mahendraparvata and a 12th century city, Preah Khan of Kompong Svay. Fields of precisely arranged earthen mounds at these settlements may have been used to collect rainwater, Evans speculates. Earthen embankments forming coiled or spiral patterns might have been gardens or ceremonial spaces.

“It’s humbling to see the lidar data and realize how much was previously missed in ground surveys at Preah Khan,” says archaeologist Mitch Hendrickson of the University of Illinois at Chicago. Hendrickson conducts research at Preah Khan, one of several ancient cities that provided food and other services to Greater Angkor via an extensive road system.

Before the 2015 lidar survey, Mahendraparvata was known “only from inscription texts and a few bits of broken-down masonry,” adds archaeologist Charles Higham of the University of Otago in Dunedin, New Zealand. Mahendraparvata’s laser-traced layout indicates it was an early, small-scale version of Greater Angkor, Higham says.
A military invasion and sacking of Greater Angkor in the 15th century apparently did not result in most of its roughly 750,000 residents abandoning the site, as many investigators have thought. Lidar data from 2015 indicate that Khmer capitals established after Greater Angkor’s defeat, such as Longvek and Oudong, show no signs of dense populations created by mass relocations from the former capital, Evans says.

That suggests that the political state collapsed at Greater Angkor, but hundreds of thousands of rice farmers carried on, Hendrickson says. “Lots of fish and rice were still available,” he says. “Local farmers were more resilient than the state was.”

Coral reefs won’t be out of hot water anytime soon. A global bleaching event that began in June 2014 is the longest on record and now covers a larger area than ever before. What’s worse, it shows no signs of ending.

Global warming exacerbated by the latest El Niño is to blame, National Oceanic and Atmospheric Administration scientists reported Monday at the 13th International Coral Reef Symposium in Honolulu. Since 1979, periodic mass bleachings covering hundreds of kilometers have only lasted for “a year or so,” said NOAA Coral Reef Watch Coordinator Mark Eakin. But this one has dragged on for two years, threatening more than 40 percent of reefs globally, and more than 70 percent in the United States.

When corals are stressed by heat, they reject the colorful algae living inside them and turn a ghostly white. Those algae are a major source of food, so reefs can die if conditions don’t improve.

NOAA scientists aren’t sure what will end this episode. It could extend into 2017, and more frequent events are possible in the future, the scientists said. “Climate models suggest that most coral reefs may be seeing bleaching every other year by mid-century,” Eakin added. “How much worse that gets will depend on how we deal with global warming.”