A previous attempt to determine how speakers’ grammatical encoding system operates in naturalistic conversation revealed than neither the addressee- nor the speaker-efficiency accounts are applied (V. S. Ferreira & Hudson, under review). The purpose of the current study is too see whether it is possible to induce speakers to use the addressee-efficiency account through the manipulation of confederate condition. Participants (n=36) took part in what they believed to be an emotion attribution game with a partner (half of participants’ partners were native English speakers, the other half’s were non-native English speakers) in which they were required to take turns reading statements and questions in response to which the other participant had to reply using sentences which could include a temporary syntactic ambiguity. Speakers could avoid producing syntactically ambiguous sentences by including the non-essential complementizer “that,” and it was therefore predicted that when addressing non-native confederates speakers should include “that” more overall and specifically to avoid producing syntactic ambiguities. However, this was found to not be the case. Instead, participants’ use of “that” was influenced by social factors such as perspective taking – speakers tended to say “that” more when adopting another’s perspective, and this effect was more pronounced when addressing non-natives – and emotion attribution – speakers tended to say “that” more when attributing emotions to another, however, when addressing non-natives speakers said “that” more when attributing emotions to oneself.