Measuring Perceived Fitness Interdependence⸺Comment on Snyczer et al. (2020)

In a recent pre-print, Snyczer et al. (2020) propose a new measure of perceived fitness interdependence, the Perceived Fitness Interdependence (PFI) scale. Fitness Interdependence has recently been defined as “the degree to which two or more organisms influence each other’s success in replicating their genes” (Aktipis et al., 2018; see also Brown, 1999; Roberts, 2005). Perceived Fitness Interdependence consequently refers to subjective perceptions of this degree of mutual influence. Before Snyczer et al. (2020) was posted as a pre-print the manuscript was submitted to a peer-reviewed journal, for which we acted as referees. In our reviews, we raised several conceptual and methodological issues that we believed may have adversely affected the development and validation of the PFI scale in its current form. Because the pre-print is not substantively different from the submission we reviewed, we believe that our concerns still merit consideration. We briefly summarise our conceptual and methodological concerns; the full reviews follow below.