All interpersonal interactions are underpinned by action: perceiving and understanding the actions of others, and responding by planning and performing self-made actions. Perception of action, both self-made and observed, informs ongoing motor responses by iterative feedback within a perception-action loop. This fundamental phenomenon occurs within single-cells of the macaque brain which demonstrate sensory and motor response properties. These 'mirror' neurons have led to a swathe of research leading to the broadly accepted idea of a human mirror system. The current review examines the putative human mirror system literature to highlight several inconsistencies in comparison to the seminal macaque data, and ongoing controversies within human focused research (including mirror neuron origin and function). In particular, we will address the often-neglected other side to the 'mirror': complementary and opposing actions. We propose that engagement of the mirror system in meeting changing task-demands is dynamically modulated via frontal control networks. (C) 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).