The cultural evolution of introspective thought has been recognized to undergo a drastic change during the middle of the first millennium BC. This period, known as the “Axial Age,” saw the birth of religions and philosophies still alive in modern culture, as well as the transition from orality to literacy—which led to the hypothesis of a link between introspection and literacy. Here we set out to examine the evolution of introspection in the Axial Age, studying the cultural record of the Greco-Roman and Judeo-Christian literary traditions. Using a statistical measure of semantic similarity, we identify a single “arrow of time” in the Old and New Testaments of the Bible, and a more complex non-monotonic dynamics in the Greco-Roman tradition reflecting the rise and fall of the respective societies. A comparable analysis of the twentieth century cultural record shows a steady increase in the incidence of introspective topics, punctuated by abrupt declines during and preceding the First and Second World Wars. Our results show that (a) it is possible to devise a consistent metric to quantify the history of a high-level concept such as introspection, cementing the path for a new quantitative philology and (b) to the extent that it is captured in the cultural record, the increased ability of human thought for self-reflection that the Axial Age brought about is still heavily determined by societal contingencies beyond the orality-literacy nexus.
Keywords: introspection, latent semantic analysis, neuroscience, Google n-grams, semantic cognition
Citation: Diuk CG, Slezak DF, Raskovsky I, Sigman M and Cecchi GA (2012) A quantitative philology of introspection. Front. Integr. Neurosci. 6:80. doi: 10.3389/fnint.2012.00080
Received: 20 June 2012; Paper pending published: 14 August 2012;
Accepted: 04 September 2012; Published online: 24 September 2012.
Edited by:Sidarta Ribeiro, Federal University of Rio Grande do Norte, Brazil
Reviewed by:Hernan Makse, City College, USA
Copyright © 2012 Diuk, Slezak, Raskovsky, Sigman and Cecchi. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.
*Correspondence: Carlos G. Diuk, Department of Psychology, Princeton Neuroscience Institute, Princeton University, Princeton, NJ 08540, USA. e-mail: firstname.lastname@example.org
† These authors equally contributed to this work.