Topic-open-endedness: Why recursion is overrated

Humans can use language to refer to and describe endless varieties of situations, thoughts, ideas, and topics, actual or hypothetical. This capacity, which distinguishes human language from communication systems of other animals, is referred to here as topic-open-endedness. A key factor in explaining topic-open-endedness early in the life of a new sign language is the nature of the linguistic symbols, the words, and the human ability to extend their meanings - e.g., through metonymy and metaphor - to novel semantic domains, applying a finite lexicon to infinite situations and topics. Other early language properties such as predication and negation facilitate creativity and flexibility from the beginning. The property of recursion accounts for the creation of an infinite number of sentences from a finite set of words and rules. But it cannot account for the open-endedness of the contents of those sentences. Therefore, the importance attributed to recursion as the sole mechanism that is uniquely human is overrated.