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

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.

Keywords: doctoral education; graduate training; mentorship; postdocs; research skills.

Fig. 1.

High-, medium-, and low-skill latent profiles, showing estimated mean scores for each research skill within each year according to the final LPTA model.

Fig. 2.

Latent profiles by time, showing minimum, maximum, means, and number of participants in each profile.

Fig. 3.

Latent growth model results, reflecting common trajectories of skill development within each latent class.

Fig. 4.

Odds ratios with 95% confidence intervals displaying significant predictors of positive transitions (year 2 to year 3, year 3 to year 4) and skill trajectories (LGCs), as well as contrasting nonsignificant predictors. Odds ratios with confidence intervals containing 1 (indicated by vertical dashed line) are nonsignificant.