A basic property of human language is that it unfolds in time; the left and right margin of discourse units do not behave in a symnmetrical fashion. The working hypothesis of this volume is that discourse elements of the left periphery have mainly subjective and discourse-structuring functions, wheras at the right periphery, such element play an intersubjective or modalising role. However, the picture that emerges from the different contributions to this volume is far more complex. While it seems clear that the working hypothesis cannot be upheld in a "strong" way, most of the chapters -especially those based on corpus data - show that an aymetry between left and right perioplery does exist and that it is a matter of frequency.
Beeching, K., & Detges, U. (2014). Discourse Functions at the Right and Left Periphery: Crosslinguistic Investigations of Language Use and Language Change. Brill