6 If grammar is the solution, what is the problem?

As it is common for children to be making some sort of over-generalisation errors when they are even 5, 6, 7 years of age, grammar is clearly a formidable challenge to acquire. Given the challenge of mastering such a complex and subtle system as grammar, one might reasonably ask, is it worth the effort?

Tomasello (2008) has advanced the theory that grammar can be thought of as the solution to problems of sharing, informing and requesting. The pressure to package these cooperative motivations in a mutually understandable way has existed for long enough in the course of human history for them to have been grammaticalised in various ways. For example, requesting help in the immediate you-and-me, here-and-now requires little in the way of grammar (e.g. ‘that, here, now’). This is language as tool-use for getting things done in the world, where it can be used to advance personal gain or achieve a shared goal. As anyone who spends time around children knows, language’s imperative function to express desire emerges robustly with the word ‘want’. Associated with a requesting motivation, children produce these forms a year or more earlier than the corresponding belief verbs and comprehend them earlier also.

Sharing – wanting to share emotions and attitudes with others – and informing – wanting to help others by informing them of useful or interesting things – requires more sophisticated linguistic strategies that can package these cooperative motives. Where there are multiple relevant objects and actions there is pressure to combine phrases (e.g. connectives) in a way that disambiguates between objects (e.g. nouns, prepositions, quantifiers), identify items or events displaced from the here-and-now (e.g. tense), how they unfold over time (e.g. aspect, adverbs) and how elements in the scene relate to each other (e.g. verbs and argument-structure constructions). Finally, the motive of expressing and sharing emotions and attitudes, particularly through narrative, requires a way to express a speaker’s relationship to an assertion (e.g. modals, evidentials) discourse-coordination devices (topic-elaboration-termination) and structure (onset-unfolding-elaboration) that enable relations to be tracked across multiple events and participants. So, grammar is part of a bigger story of cooperative behaviour because that is the medium in which informing, sharing and requesting works.