Vogt, P. (In press) On the acquisition and evolution of compositional languages: Sparse input and the productive creativity of children. Adaptive Behavior Special issue on Evolution and Acquisition of Language. In press.

Abstract This paper investigates the productive creativity of children in a computational model on the emergence and evolution of compositional structures in language. In previous models it was shown that compositional structures can emerge in language when the language is transmitted from one generation to the next through a transmission bottleneck. Due to the fact that in these models language is transmitted only in a vertical direction where adults only speak to children and children only listen, this bottleneck needs to be imposed by the experimenter. In the current study, this bottleneck is removed and instead of having a vertical transmission of language, the language is -- in most simulations -- transmitted horizontally (i.e. any agent can speak to any other agent). It is shown that such a horizontal transmission scenario does not need an externally imposed bottleneck, because the children face an implicit bottleneck when they start speaking early in life. The model is compared with the recent development of Nicaraguan Sign Language, where it is observed that children are a driving force for inventing grammatical (or compositional) structures, possibly due to a sparseness of input (i.e. an implicit bottleneck). The results show that in the studied model children are indeed the creative driving force for the emergence and stable evolution of compositional languages, thus suggesting that this implicit bottleneck may -- in part -- explain why children are so typically good at acquiring language and, moreover, why they may have been the driving force for the emergence of grammar in language.