touch her on the shoulder还是touch her shoulder?

复旦大学编写的《大学英语·精读》第三册第五单元中有这样一句话:“I approached cautiously and touched her shoulder.”(我小心地向她走去,轻轻拍拍她的肩膀。)在几次教到这一句子时都有学生提出应当把这句话中的touched her shoulder 改为 touched her on the shoulder。并说他们中学时,老师讲 touch her shoulder 是错误的。有的书刊也有这样的说法。由此可见这一问题比较普遍。