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Discovered: Chimps pick their fights; marijuana damages young minds; learn while sleeping; arctic sea ice takes a dive.

Just say no, kids. Dim-witted teenage stoners have long held a place in the popular imagination. And now, science is confirming that weed might damage young brains in a way that it does not for adults. Researchers from King's College in London and Duke University teamed up to study 1,000 New Zealanders from birth to 38 years of age, gauging the effect that regular marijuana use has on the brain. They found that those who habitually inhaled during their teenage years experienced IQ drop-offs later in life, while those who began smoking only after the age of 18 held their IQs stable. "It's such a special study that I'm fairly confident that cannabis is safe for over-18 brains, but risky for under-18 brains," says King's College professor Terrie Moffitt. [The Guardian]

Arctic sea ice at lowest recorded point yet. Today marks yet another sad and scary milestone in our world's inability to stave off the effects of climate change. The University of Colorado National Snow and Ice Data Center has reported that Arctic sea ice hit an all-time low, and will likely only continue to decline over the weeks to come. They calculate that Arctic sea ice cover has shrunk down to 1.58 million square miles. Bill Clinton's deputy assistant secretary of state for environment and development Rafe Pomerance says that this marks "a profound moment that will change the debate" about climate change. The cruel punch-line here is that the low sea levels have made it possible for Royal Dutch Shell’s drill ship, the Noble Discoverer to navigate through Alaska's Dutch Harbor and in to the Chukchi Sea, where they'll conduct oil exploration. [The Washington Post]

Chimps are selective fighters. Humans have a way of holding a grudge even against those who've never personally done anything to them. We enact punishments on those utterly unconnected to us through politics, prejudice and our justice system. "Third party punishment" is trait distinct to human societies, researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany believe. Katrin Riedl and colleagues studied chimpanzees and determined that, "In contrast to humans, chimpanzees do not engage in third-party punishment." She put chimps through a scenario involving a food thief, their victim and an actor. She found that chimps only attacked the chimps who stole their food directly from them, and didn't involve the third party actor chimp. Keith Jensen, a researcher involved with Riedl's study, says, "This might explain, in part, how we have been uniquely able to form large-scale societies of unrelated individuals." [Discover]

Sleep while getting smarter. Imagine if all that time you spent sleeping, you were learning as well. How knowledgable you'd be! Well, we might not be able to read or solve math problems, but researchers at Israel's Weizmann Institute of Science have demonstrated that our brains can be trained by smells while we slumber. "We know we can consolidate the day's information while we sleep," says researcher Anat Arzi. "But attempts to teach new facts using verbal information have failed." So instead, Arzi and his colleagues released aromas and accompanying sounds on sleeping test subjects. Pleasant smells caused the sleeping patients to breathe deeply, while unpleasant smells made them sniff nervously. After awhile, the subjects could be provoked to breath deep or sniff quickly solely by hearing the sounds, which shows that they learned something while sleeping. Commenting on the research, NYU's Donald Wilson says, "We thought the olfactory system went offline during sleep, but this study shows that some information is going in and being retained."  [New Scientist]

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