Language background shapes third-party communication expectations in 14-month-old infants.

Infants expect native and non-native speech to communicate, i.e. to transfer information between third-parties. Here, we explored if infants understand that communication depends on the use of shared conventional systems (e.g. speaking the same language), and if linguistic input (monolingual vs. bilingual) influences infants' expectations about who can communicate with whom. Fourteen-month-old monolingual and bilingual infants were presented with two actresses who spoke distinct languages (Experiment 1) or the same foreign language (Experiment 2). At test, one of the actresses uttered a foreign-language sentence (communicator) to inform the other actress (recipient) about her preference for one of two objects she could not reach. Infants expected effective communication between the two actresses when they belonged to the same linguistic group. When they demonstrated to speak distinct languages, however, only bilinguals expected that the communicator's message would be effectively transmitted to the recipient -they found more surprising the condition in which the recipient gave to the communicator the non-preferred object (vs. the preferred). The results suggest that infants expect speech to convey information between third-parties only when individuals share the same conventional system. In addition, the results suggest that, unlike monolinguals, bilinguals expect speakers of their native-language to have access to multiple conventional systems.