“…While PPIs were taken to be less interesting than NPIs in earlier literature (e.g., Horn, 1989 ), they have been gaining more attention recently (e.g., Szabolcsi, 2004 ; Homer, 2011 ; Liu, 2017 ; Nicolae, 2017 ; Zeijstra, 2017 ; Hoeksema, 2018 ). Theoretical accounts of PPIs are, however, highly biased by NPI theories, in that they often assume a parallelism between NPIs and PPIs.…”