Research on teachers' talk has found that teachers of a target language tend to modify their speech in order to assist learners' comprehension of the message during the interaction. Most studies focus on the manner in which teachers change their linguistic or interactional features of their speech. This study examined how native-speaking teachers of a foreign language (JFL) modify their back channel behavior (i.e. listener's short message occurring within the speaker's turn that does not relinquish its message) as listeners during the interaction with JFL learners (Yngve, 1970). This listener's message to the speaker in Japanese conversation, namely, 'aizuchi' plays an important interactional role in establishing harmonious relationships and the emotional bond between the interlocutors that are regarded as one of the principal cultural norms (Mizutani, 1986). It was assumed that Japanese teachers might modify their back channels when they interact with FL learners, base! d on the features of teachers' talk, as well as interactional characteristics of Japanese conversation.
Two types of interaction (1) NS-NNS (NS is a teacher, and NNS is a FL learner); and (2) NS-NS (both NSs are teachers) were compared in terms of the NSs' behaviors in aizuchi. The NSs' aizuchi were examined in terms of: (a) frequency of occurrences; (b) linguistic forms; (c) location of occurrences in relation to speaker's turns (i.e. during or between speaker's turns); and (d) functions in interaction. It was discovered that aizuichi occurs more frequently but exhibit less linguistic variations in NS-NNS than NS-NS interaction. Although the distribution of the aizuchi exhibits no significant differences between the two interactions, there was a specific aizuichi occurring only in NS-NNS interaction: NSs' evaluative aizuchi (i.e. recasts, repeats with rising intonation) to NNSs. Teachers' evaluative functions of aizuichi are also argued with respect to roles as feedback signals to learners.