h_a: the scientist as chimpanzee or bonobo

In a recent paper, Hirsch (h_a: an index to quantify an individual’s scientific leadership, 2019. https://doi.org/10.1007/s11192-018-2994-1) proposes to attribute the credit for a co-authored paper to the a-author—the authors with the highest h-index—regardless of his or her actual contribution, effectively reducing the role of the other co-authors to zero. The indicator h_a inherits most of the disadvantages of the h-index from which it is derived, but adds the normative element of reinforcing the Matthew effect in science. Using an example, we show that h_a can be extremely unstable. The empirical attribution of credit among co-authors is not captured by abstract models such as h, h¯, or h_a.