ABSTRACT
Humans share with other species the ability to associate sounds and meanings in a particular way (Kaminski, Call and Fisher 2004). However, the unbounded nature of the association is uniquely designated to humans. While other species convey a limited, fixed array of meanings by using a rigid order of body motions, humans convey an unbounded set of different meanings by using language. This unique property of unboundedness is generated by the internalized mechanisms (internalized language, I-language) in the brain. The basic property of I-language is to provide “an unbounded array of hierarchically structured expressions that receive interpretations at two interfaces, sensorimotor for externalization and conceptual-intentional for mental processes”(Chomsky 2013: 647). Linear order is a part of externalization required by properties of the sensorimotor system, during the process of which hierarchical structure is mapped onto linear sequences of words. Linear or sequential information is not specific to humans. In this sense, hierarchical structures are a defining feature of human language, forming a division between human and nonhuman communication systems (Anderson 2008; Moro 2011).
