Adults' use of infant-directed special vocabulary and its relation to children's language development

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K13468
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Educational psychology
• Research Institution: The University of Tokyo
• Principal Investigator: Haryu Etsuko 東京大学, 大学院教育学研究科(教育学部), 教授 (70276004)
• Research Collaborator: SAITO Yuka
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 乳児 / 言語 / 育児語 / 発達 / 養育

Outline of Final Research Achievements

Japanese adults use ikujigo, infant-directed special vocabulary, only when they talk to infants. In ikujigo, onomatopoetic words (e.g., wanwan ‘bowwow’ for inu ‘dog’) or reduplications (e.g., kuQku for kutsu ‘shoe’) are frequently used instead of regular adult forms.
We conducted a cross-sectional and two longitudinal studies to investigate whether mothers fine-tune the use of ikujigo according to their children's development, as well as whether their use of ikujigo contributes to children's word learning. The results showed that mothers increase the number of ikujigo they use after their children's first birthday and decrease it by their children's second birthday. Additionally, not mean but range of the number of ikujigo a mother used across the child's development positively correlated with the child's vocabulary at 24 months, suggesting that not ikujigo-use per se but mothers’ sensitivity to their children’s developmental level may foster children’s word learning.

Free Research Field

発達心理学

Academic Significance and Societal Importance of the Research Achievements

大人は、乳児向けに話しかける時には、犬のことをワンワンと呼ぶなど、大人どうしの会話では使わないような単語、つまり育児語を使用する場合がある。これについては、本来、”犬”に対して覚えるべきラベルである「イヌ」の学習を妨げるのではないか、あるいは、いったん「ワンワン」と覚えても、結局はそれを別の単語「イヌ」に置き換えなければならないため、かえって負担ではないか、という声も聞かれる。
しかし、実情としては、親は子どもの発達レベルに合わせて、このような単語の使用量を変化させており、育児語の使用は子どもの言語発達に害を及ぼしていないことが明らかになった。