Postdocs’ lab engagement predicts trajectories of PhD students’ skill development

Significance

Conventional wisdom in the laboratory sciences suggests that PhD students develop their research skills as a function of mentorship from their faculty advisors (i.e., principal investigators; PIs). However, no prior research has identified empirically a relationship between specific PI practices and the development of research skills. Here we show that PIs’ laboratory and mentoring activities do not significantly predict students’ skill development trajectories, but the engagement of postdocs and senior graduate students in laboratory interactions do. These findings support the practice of “cascading mentorship” as differentially effective and identify a critical but previously unrecognized role for postdocs in the graduate training process. They also illustrate both the importance and the feasibility of identifying evidence-based practices in graduate education.

Abstract

The doctoral advisor—typically the principal investigator (PI)—is often characterized as a singular or primary mentor who guides students using a cognitive apprenticeship model. Alternatively, the “cascading mentorship” model describes the members of laboratories or research groups receiving mentorship from more senior laboratory members and providing it to more junior members (i.e., PIs mentor postdocs, postdocs mentor senior graduate students, senior students mentor junior students, etc.). Here we show that PIs’ laboratory and mentoring activities do not significantly predict students’ skill development trajectories, but the engagement of postdocs and senior graduate students in laboratory interactions do. We found that the cascading mentorship model accounts best for doctoral student skill development in a longitudinal study of 336 PhD students in the United States. Specifically, when postdocs and senior doctoral students actively participate in laboratory discussions, junior PhD students are over 4 times as likely to have positive skill development trajectories. Thus, postdocs disproportionately enhance the doctoral training enterprise, despite typically having no formal mentorship role. These findings also illustrate both the importance and the feasibility of identifying evidence-based practices in graduate education.