自50年代末喬姆斯基的語(yǔ)言學(xué)理論問(wèn)世以來(lái)，許多語(yǔ)言學(xué)家對(duì)以英語(yǔ)為母語(yǔ)的少兒的語(yǔ)言進(jìn)行研究，發(fā)現(xiàn)隨著年齡的增長(zhǎng)，少兒的語(yǔ)言技能日趨成熟，其中一個(gè)明顯標(biāo)志是句子長(zhǎng)度和復(fù)雜程度不斷增加。在字?jǐn)?shù)相同的作文中，語(yǔ)言技巧越嫻熟的，句子的數(shù)目就越少，這意味著句子越長(zhǎng)，結(jié)構(gòu)越復(fù)雜，句子的意義含量就越大。根據(jù)這一理論，美國(guó)語(yǔ)言學(xué)家和教師進(jìn)行了大量的寫(xiě)作教學(xué)法研究，發(fā)現(xiàn)合并句子（combining sentences）有助于促進(jìn)語(yǔ)言技巧成熟。當(dāng)然，長(zhǎng)句和短句各有優(yōu)點(diǎn)，在寫(xiě)作中它們應(yīng)適當(dāng)交叉使用，相互補(bǔ)充，使文章波瀾起伏，錯(cuò)落有致，增加語(yǔ)言表現(xiàn)力。但一連串的短句會(huì)使人感到幼稚，有必要將它們合并。例如：
短句：I returned to my room．There was a note under my door．It was from Bill．He said he was in the town looking for a job．He hadn't found anything yet．He was sorry to have missed me．（各句的詞數(shù)是5＋7＋4＋11＋5＋7）
合并：When I returned to my room，I found a note from Bill under the door．He said he was in the town looking for a job，but hadn't found anything yet．He added that he was sorry to have missed me．（15＋16＋10）
短句：I returned to my room．There was a note under my door．It was from Bill．He said he was in the town looking for a job．He hadn't found anything yet．He was sorry to have missed me．（各句的詞數(shù)是5＋7＋4＋11＋5＋7）
合并：When I returned to my room，I found a note from Bill under the door．He said he was in the town looking for a job，but hadn't found anything yet．He added that he was sorry to have missed me．（15＋16＋10）