Science  30 Aug 2013:
Vol. 341, Issue 6149, pp. 944

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  1. Learning Language in the Womb


    As a fetus grows inside a mother's belly, it can hear sounds from the outside world—and can retain memories of them after birth, according to a study online this week in the Proceedings of the National Academy of Sciences.

    The sound-processing parts of a fetus's brain become active in the last trimester of pregnancy, and sound carries fairly well through the mother's abdomen, says cognitive neuroscientist Eino Partanen of the University of Helsinki. He and his team outfitted babies with EEG sensors to look for neural traces of memories from the womb; hearing a repeated sound forms a memory, he says, which speeds up recognition of sounds and can be detected as a pattern of brain waves—even in a sleeping baby.

    The team gave expectant women a recording to play several times a week during their last few months of pregnancy, which included a made-up word, "tatata." By the time the babies were born, they had heard the made-up word, on average, more than 25,000 times. When they were tested after birth, these infants' brains recognized the word, while infants in a control group did not.

  2. Slower Warming Tied to Pacific Cooling

    Although greenhouse gas concentrations continue to rise, over the last 15 years there has been a puzzling "hiatus" in the rise of global mean temperatures. Some scientists have suggested that this hiatus may be due to increasing amounts of aerosols, or to the solar activity minimum in 2009. But a new study in Nature has identified a different cause: variability in tropical Pacific sea-surface temperatures.

    Climatologist Yu Kosaka of the Scripps Institution of Oceanography in San Diego, California, and colleagues examined the effect of periodic cooling in the eastern equatorial Pacific Ocean using several different model experiments and compared these with the observed records. In one model, they incorporated only the increased greenhouse gas concentrations, aerosol concentrations, and solar cycle changes. In the second, they fixed these at 1990 levels, but included changes in sea-surface temperatures in the equatorial Pacific. In the third model, they incorporated both. That model, they found, best reproduced the observed records. Together, Kosaka says, the models suggest that a cooling trend in this patch of ocean from 2002 to 2012 was responsible for the mysterious hiatus.