Bill had moved from Cleveland to Shanghai on a job assignment. Whenever someone came to his apartment door, Bill brought his three-year-old daughter, Natalie, to the door to translate from Chinese to English. Both Bill and Natalie had moved to China at the same time, two years ago, but Natalie had picked up Chinese at a rate that left Bill in the dust. Although we don’t fully understand why it is easier for younger children to learn new languages than for older children and adults, learning a language does appear to have what psychologists call a(n) ________, an interval when people are receptive to learning and can acquire new knowledge more easily.