(S (S (S (NP (BASENP (RB About) (NN half)) (PP (IN of) (BASENP (NNS boys)))) (VP (VBD reported) (S (VP (VBG masturbating) (ADVP (ADVP (RB twice) (CC or) (RBR more)) (PP (IN per) (BASENP (NN week)))))))) (COMMA ,) (S (ADJP (ADJP (RB also) (JJR higher)) (PP (IN than) (NP (NP (DT the) (BASENP (NN 23) (NN percent))) (PP (IN of) (BASENP (NNS girls)))))))) (PERIOD .))