Sentence:  Irregular bedtimes may disrupt healthy brain development in <WSD>young</WSD> children, according to a study of intelligence and sleeping habits.  &para; Going to bed at a different time each night affected girls more than boys, but both fared worse on mental tasks than children who had a set bedtime, researchers found. 
Meaning of the word marked with <WSD> tags:  In the early part of growth or life; born not long ago.