This article grasps the coercive character often associated to research impact metrics, in the wake of the ever-growing use of quantitative indicators for the evaluation of the academic performance. It does so by taking a Marxian perspective which underscores what are the historically determined attributes of academic labour that the functioning of impact metrics embodies, unfolding thereby what ‘impact’ really means concerning said social attributes of the scientific enterprise. Science communication via social media, and the array of metrics and indicators (...) surrounding it, known as alternative metrics or altmetrics, are taken as a case study. This study concludes that the coercive nature of research impact metrics is grounded on the private and independent character taken by social labour in capitalist production, an historically determined form of the social reproduction that asks for academic production to be organised and regulated in an indirect fashion, behind the backs of producers themselves – in the particular case of science, by means of quantitative indicators and performance metrics. As research impact metrics bear the power to determine how and to what extent academic labourers contribute to the general productive process, their will and consciousness become thus subsumed to such reified social subject. (shrink)