A new study suggests some language learning can take place during sleep. Researchers from Switzerland’s University of Bern say they discovered people were able to learn new language words during deep levels of sleep. Results of the study recently appeared in the publication Current Biology. Sleeping hours are generally considered unproductive time. But several studies have suggested some learning activity can happen. Studies involving mice provided evidence that sleep learning is possible in the brain of mammals. Other human studies, the Swiss researchers said, found that simple learning through sounds may be possible during sleep. But they added that “complex verbal learning” has not yet been demonstrated.