I just discovered (via Tyler Cowen) a fascinating economics paper on the changing dynamics of scientific production over the 20th century. A few months ago, I wrote about the tangled relationship of age and innovation, and why different fields have different peak ages of creativity. In general, math, physics and poetry are for the young, while biology, history and the social sciences benefit from middle-age:
Interestingly, these differences in peak age appear to be cultural universals, with poets peaking before novelists in every major literary tradition, according to [Dean] Simonton’s research.
What accounts for these variations? Mr. Simonton suggests that they’re caused by intrinsic features of the disciplines. Those fields with a logically consistent set of principles, such as physics and chess, tend to encourage youthful productivity, since it’s relatively easy to acquire the necessary expertise. (The No. 1 ranked chess player in the world today, Magnus Carlsen, is 19 years old.) Because the essential facts can be quickly learned, and it usually doesn’t take that long to write a lyric poem, the precocious student is free to begin innovating at an early age.
In contrast, fields that are loosely defined and full of ambiguous concepts, such as biology and history, lead to later peak productive ages. After all, before a researcher can invent a useful new idea, he or she must first learn an intimidating assortment of details.
This new economics paper, by Benjamin Jones at Northwestern, describes a fascinating natural experiment that captures this dynamic at work:
Jones and Weinberg further analyze the effect of an exogenous shock to the foundational knowledge in a field, studying the age and training patterns around the quantum mechanics revolution in physics. The quantum mechanics revolution is typically charted between 1900 and 1927. Remarkably, we find that (a) age at great achievement and (b) age at Ph.D. actually declined in physics during this period, reaching a minimum just as quantum mechanics becomes a rigorously established theory in the late 1920s and then rising thereafter. Moreover, these patterns are unique to physics; the age of great achievements and Ph.D. age in other fields continued to rise during this period. Viewed as a natural experiment, the analysis of the quantum mechanics revolution further substantiates the link between the current depth of knowledge in a field, its training requirements, and the ensuing innovative output of young scholars.
Why were young physicists better at working on quantum mechanics, at least in the early part of the 20th century? One possibility is that the youthful brain is intrinsically more creative, and thus better able to contemplate the surreal properties of subatomic particles. In other words, the creativity of youth is really a story about cognitive decline and the inevitable atrophy of the human cortex. But that’s almost certainly not the case. (After all, some academic fields, such as literary criticism, have a peak creative age in the late forties.) Instead, Simonton and others argue that young physicists benefit, at least in part, from their outsider status – they’re more innocent and ignorant – which makes them more willing to embrace novelty and surprise. Because they haven’t become “encultured,” or weighted down with too much conventional wisdom, they’re more likely to rebel against the status-quo and explore the the spooky ideas of Schrodinger, Bohr, et. al. After a few years in the academy, however, Simonton says that “creators start to repeat themselves, so that it becomes more of the same-old, same-old.” They have become insiders, invested in Newtonian mechanics; that is what they know and that is what they believe in. It’s only the impetuous youth, those marginal figures without tenure or grants of their own, who properly appreciate the anomalies of the subatomic world.
What makes this “natural experiment” so convincing is that it counters the larger trend of 20th century science, in which the peak age of scientists got older and older. (According to Jones, the peak age was extended by approximately five years during the 20th century.) This is largely a side-effect of scientific success: researchers discovered a lot of new facts, which meant that it took a few additional years to master any given field.
I’d be interested in seeing if this same pattern holds true for every paradigm shift/scientific revolution. Did the rise of molecular biology lead to a decrease in the peak age of molecular biologists? What about the modern synthesis in evolutionary biology? Or the rise of the modernist novel? Alternatively, it’s also possible that the quantum revolution was a relatively unique scientific moment, an “exogenous shock” that was unusually shocking.