This article offers a comparative analysis of “predicative” gerunds (“PGs”) and prepositional infinitives (“PIs”), focussing on perception constructions in Spanish (PGs) and European Portuguese (PIs). I demonstrate that these two constructions are diachronically related and that they still have a similar syntax. The evidence discussed suggests that both constructions are Small Clauses headed by a preposition of central coincidence. In PGs, this preposition is merged in a low aspectual projection and incorporates into the verb. In PIs, an evolution of PGs, it is merged later in the structure. This leads to a layering process, i.e. the splitting of a single head into a series of heads and transferring the semantics of one functional head to more heads. Thus, PIs have a more expanded structure than gerunds. Finally, further empirical evidence for this analysis is discussed, such as the insertion of adverbs and the use of sin (“without”) to negate the perceived event.