Theoretical and Experimental Research on Grammatical Development and Attrition in the Process of Second Language Acquisition

调查的目的是对以下问题进行研究：第二语言对第一语言的影响;第一语言熟练程度的保持和/或丧失;第二语言熟练程度的获得、保持和可能丧失。我们调查了变化的原因（如果发生了任何变化），并提出了儿童或语言学习者进一步发展语言所需的教育类型。主要研究结果如下：（1）关于居住在日本的外国儿童的第一语言损失，一些儿童表现出增益，而另一些儿童则表现出损失的认知能力。中国儿童普遍观察到L2日语的发展，但菲律宾儿童之间存在差异。(2)日本留学生在听力和语法方面没有损失。(3)学习英语的日本人和西班牙人，以及学习日语的中国人和英语学习者在他们的第二语言中观察到了一些母语效应。

The purpose of the investigation was to conduct research on the following issues: The influence of a second language on one's first language (L1); the maintenance and/or the loss of proficiency in the L1 and the acquisition, maintenance and possible loss of proficiency in the second language (L2). We have investigated the causes of change (if any change has taken place) and proposed the type of education a child or a language learner needs for further language development. The main findings are the following:(1) Regarding the L1 loss of foreign children who reside in Japan, some children showed gain while others showed loss in their cognitive ability. Chinese children generally observed development in L2 Japanese but there was a variation among Filipino children. (2) Japanese returnees showed no loss in their listening abilities and grammar in L2 English. (3) Japanese and Spanish learners of English and English and Chinese learners of Japanese observed some L1 effects in their L2.