Mastery begins with a firm grounding in foundational competencies in many professional fields. Whether it is a computer programmer requiring a robust grasp of basic mathematics, a nurse building clinical acumen before progressing to the role of a nurse practitioner, or a negotiator whose persuasive capacity rests on clear communication and active listening, initial skill development is essential. These early proficiencies form the bedrock upon which more complex, specialised abilities are constructed. Without this grounding, advancement within a profession becomes difficult and, in many cases, unfeasible.

A recent study in Nature Human Behaviour offers a novel empirical framework for understanding this phenomenon. Drawing from millions of job transitions and extensive data from U.S. workplace surveys, the researchers mapped the interdependencies among job-related skills. Their findings revealed a distinct “nested” structure within many professions, where more advanced competencies are built upon the mastery of broader, more general skill sets. This structure is not merely academic; it has tangible consequences for economic inequality, workforce stratification, and career mobility within today’s increasingly specialised labour market.

Lead author Moh Hosseinioun, a postdoctoral fellow at Northwestern University, highlights this layered dynamic: “We found that many skills aren’t just complementary — they’re interdependent in a directional way, acting as prerequisites for others, snowballing layer over layer to get to more specialised knowledge.” In this schema, professional advancement resembles a scaffolding in which one must secure basic rungs before accessing more specialised tiers. Such an architecture fosters cumulative learning, where each successive level is contingent upon mastery of the previous.

The research’s origins lie in a broader inquiry into how occupational categories like “white-collar” and “blue-collar” emerge. According to SFI External Professor Hyejin Youn of Seoul National University, a corresponding author on the study, the distinction often lies in the specialisation mode. Knowledge-intensive careers typically demand extensive educational investment and prolonged training, whereas more physically oriented roles can be learned through on-the-job experience. This dichotomy suggests a fundamental divergence in how various sectors approach skill acquisition and professional growth.

Youn further draws a compelling analogy from ecology to describe how this nested structure unfolds. Like ecological succession — in which microbes prepare the soil for plants, which sustain herbivores and eventually predators — human cognitive development proceeds in stages. “Advanced problem-solving — like solving partial differential equations — first depends on mastering arithmetic, understanding mathematical notation, and grasping logical principles,” she notes. Foundational educational skills are akin to the early organisms that create the conditions for more complex forms of life, or in this case, higher-order reasoning.

Although the hierarchical nature of skill development may seem self-evident, the implications are far from trivial. The researchers found that the most deeply nested skills are associated with longer educational timelines, higher wage premiums, and more excellent resistance to automation. As skill chain complexity increases, so does the exclusivity of roles positioned at their apex. This deepening stratification risks intensifying job market polarisation, particularly for individuals who lack access to strong educational foundations early in life.

This structural reality presents significant challenges for policymakers. The growing entrenchment of nested skill hierarchies may hinder social mobility, limiting access to higher-wage professions for those without early exposure to foundational education. As Youn cautions, “The more we become specialised and nested, the more inequality and disparity across the labour market will occur.” The findings suggest that while well-intentioned, short-term ‘reskilling’ initiatives may be ineffective unless paired with sustained investment in basic educational infrastructure.

Educational institutions are also implicated in this shifting landscape. A growing trend among universities to prioritise market-ready skills over general foundational learning may backfire in the long term. By neglecting the essential building blocks of reasoning, analysis, and communication, graduates may find themselves ill-equipped to develop the specialised skills that today’s labour markets increasingly demand. The erosion of foundational learning could thus inadvertently diminish future adaptability and career resilience.

Finally, the advent of artificial intelligence introduces new complexities. As AI systems, huge language models, become adept at handling fundamental tasks, a pressing question arises: does outsourcing these skills facilitate or inhibit human learning? “Large language models are unprecedented in how they target fundamental skills,” notes Hosseinioun. While such technologies might accelerate access to specialised knowledge by bypassing certain learning stages, they could also undermine our capacity to develop the competencies on which advanced reasoning depends. In an era of accelerating technological change, the challenge lies in acquiring knowledge and understanding how its acquisition is structured — and what that means for individuals and societies alike.

More information: Moh Hosseinioun et al, Skill dependencies uncover nested human capital, Nature Human Behaviour. DOI: 10.1038/s41562-024-02093-2

Journal information: Nature Human Behaviour Provided by Santa Fe Institute