Based on data from Altmetric.com. Altmetric is supported by Macmillan Science and Education, which owns Nature Publishing Group.

Amid increased competition for faculty jobs in biomedicine, some have suggested cutting the number of PhD students. So when a senior scientist advised against this, the online world took notice. Eve Marder, a neuroscientist at Brandeis University in Waltham, Massachusetts, argued in the journal eLife that it is hard to predict who will excel in science, so any attempt to limit access to PhD programmes will inevitably exclude potential stars. The reaction was mixed. “Reduce the number of admitted graduate students? Agree with Eve Marder: not the greatest idea,” tweeted Sergey Kryazhimskiy, an evolutionary biologist at Harvard University in Cambridge, Massachusetts. But Mike White, a geneticist at Washington University School of Medicine in St. Louis, Missouri, argued in a blog post that Marder was “perpetuating the PhD pyramid scheme”. See go.nature.com/t9tgts for more.