Around fifteen years ago, a major science journal asked leading researchers to picture the coming decade. Most answers were sober—emissions paths, growth curves, demographic projections. One was strange. Peter Turchin, who had begun his career as a theoretical biologist before turning his quantitative tools on history, told them the U.S. was moving toward a serious internal crisis around 2020. Polarization would harden. Trust in shared institutions would crack. Political violence would surface in ways most Americans alive had never seen (Turchin, 2010).
By the end of the decade, the forecast was hard to chalk up to luck.
What Turchin practices has a name now: cliodynamics. The premise is unromantic but powerful. History is not just a parade of singular accidents. It is a system, and like other systems, it has pressures that recur. When wages stall for decades while costs climb, when too many ambitious people are competing for too few elite positions, and when the institutions designed to absorb conflict start losing their grip, the chance of disorder rises. The model never predicts the spark. It predicts that some spark, somewhere, will catch.
Late-Republican Rome, the Bourbon endgame in France, and the interwar 1930s all sit, perhaps uncomfortably, inside the same family of curves.
A quieter movement was taking shape on the psychology side of the academy in roughly the same years. It extended Turchin’s logic from structure to mind. Societies don’t only have measurable structural rhythms; they have measurable psychological ones, and those shift with the structures.
For most of the discipline’s modern life, psychology had not really thought this way. The instinct was to study the mind the way a physiologist studies a heart: same organ everywhere, with culture and history adding flavor on top. Participants were drawn from contemporary, prosperous, educated democracies and quietly treated as proxies for humanity at large. Henrich, Heine, and Norenzayan (2010) called this the WEIRD problem— Western, Educated, Industrialized, Rich, and Democratic— and made a hard-to-shake case that the field had built a universal science from one of its strangest samples.
What was missing for a long time were the tools to study other minds, including dead ones.
Now they exist. A word vector trained on two centuries of newspapers can show, in a few minutes of computation, how the cluster of associations around a word like honor or woman drifted across decades. A custom dictionary can trace how often any psychological vocabulary you care to define rose or fell. Human coders, paired with a supervised classifier, can read a million pages of court records or sermons or diaries the way a single ethnographer once read a few hundred. Muthukrishna and his colleagues (2020) call the emerging discipline historical psychology, and the early findings are sharper than the field expected.
Schulz and colleagues (2019) showed that the parts of Europe most thoroughly reorganized by the medieval Catholic Church—its bans on cousin marriage and other dense kin arrangements—are precisely the parts whose populations now score highest on individualism, impersonal trust, and willingness to cooperate with strangers. The mind we tend to call “modern” looks, in this light, like an artifact of a thousand-year reorganization of family life. Greenfield (2013), counting words across two centuries of American books, traced a long upward arc of individualistic vocabulary—“I” rising as “we” fell.
The reason cliodynamics and historical psychology belong together is that neither is complete on its own. Structural pressure tells you a society is moving toward strain. What that strain does once it lands inside human heads is a psychological question, and it is the one historical psychology can finally start answering with measurements. Why do minds under sustained uncertainty begin to prefer simple stories to complicated ones? Why do authoritarian voices start sounding reassuring? Why conspiracy thinking stops looking eccentric (Biddlestone et al., 2025)?
The question of why a country fractures rather than reforms is, in the end, about how citizens’ minds respond to a structural situation. Both halves have to be modeled together. Atari and his colleagues (2025) give the joint project a name—the chronospatial turn— and lay out what it would take to do well: data with both time stamps and geographic coordinates, theory that travels across centuries instead of fitting a single decade, and serious collaboration with economists, historians, and computational linguists. None of those pieces is hypothetical. All of them are sitting on the workbench.
The everyday stakes are bigger than the abstraction makes them sound. If you can quantify the way a society’s psychology bends under pressure, you can begin to evaluate which interventions actually relieve the bend and which only postpone it. The same logic applies to reforms aimed at restoring institutional trust. And you can notice when your own moment fits a pattern that has shown up before. Turchin saw 2020 from 2010 because he could read the arithmetic of late Roman politics and pre-revolutionary France into early-twenty-first-century America. The numbers had been there for years.
Psychology Essential Reads
Psychology spent its first century and a half answering one question carefully: what is happening inside this person’s head, here, now. The harder questions are about minds that no longer exist and minds that don’t quite exist yet. Reading the dead, it turns out, is a useful way of forecasting the living.