[1] Pseudogapping occurs in comparative and contrastive contexts, so it appears often after subordinators and coordinators such as if, although, but, than, etc.
[3] But unlike gapping (but like VP-ellipsis), pseudogapping occurs in English but not in closely related languages.
Pseudogapping was first identified, named, and explored by Stump (1977) and has since been studied in detail by Levin (1986) among others, and now enjoys a firm position in the canon of acknowledged ellipsis mechanisms of English.
Each pair draws attention to the similarities and differences across the two closely related ellipsis mechanisms.
The examples so far illustrate that pseudogapping is like gapping insofar as the remnants of both ellipsis mechanisms must stand in contrast to the parallel expressions in the antecedent clauses.