J Speech Lang Hear Res. 2014 Apr 1;57(2):484-94. doi: 10.1044/2013_JSLHR-L-12-0354.
PURPOSE Evidence from children's spontaneous speech suggests that utterance length and utterance position may help explain why children omit grammatical morphemes in some contexts but not others. This study investigated whether increased utterance length (hence, increased grammatical complexity) adversely affects children's third person singular -s production in more controlled experimental conditions. METHOD An elicited imitation task with 12 Australian English-speaking children ages 2;9 (years;months) to 3;2 (Mage = 2;11) was conducted comparing third person singular -s production in 3-word and 5-word utterances, both utterance medially (e.g., He sits back; He sits back and swings) and utterance finally (e.g., There he sits; That's the way he sits) using a within-subjects design. Children were shown pictorial representations of each utterance on a computer and were invited to repeat 16 pseudorandomized prerecorded utterances. Acoustic analysis determined the presence/absence and duration of the third person singular morpheme. RESULTS Third person singular production was significantly lower utterance medially compared to utterance finally for the 5-word utterances and significantly lower utterance medially in the 5-word compared to 3-word utterances. CONCLUSION These results suggest that increased utterance length results in significantly lower third person singular production, but only in the more articulatorily challenging utterance-medial position. Thus, morpheme omission is greatest at the intersection of grammatical and phonological complexity.
儿童自发言语的证据表明，话语长度和话语位置可能有助于解释为什么儿童在某些语境中省略语法形态，但在其他语境中不省略。本研究调查了在更受控制的实验条件下，话语长度的增加（即语法复杂性的增加）是否会对儿童第三人称单数-s 的产生产生不利影响。
对 12 名澳大利亚英语儿童（年龄 2 岁 9 个月至 3 岁 2 个月，Mage=2 岁 11 个月）进行了诱发模仿任务，比较了 3 词和 5 词话语中第三人称单数-s 的产生，在这两种情况下，词都位于句中（如 He sits back; He sits back and swings）和句末（如 There he sits; That's the way he sits），采用了被试内设计。儿童在计算机上看到每个话语的图片表示，并被邀请重复 16 个随机预录制的话语。声学分析确定了第三人称单数形态的存在/缺失和持续时间。
对于 5 词话语，句中位置的第三人称单数产生明显低于句末位置，而 5 词话语中的第三人称单数产生明显低于 3 词话语。
这些结果表明，话语长度的增加导致第三人称单数的产生显著降低，但仅在更具发音挑战性的句中位置。因此，形态省略在语法和语音复杂性的交叉点上最大。
