The inflected/non-inflected infinitive alternation in Portuguese adverbial clauses. A corpus analysis

•The alternation inflected/non-inflected infinitive in Portuguese is examined.•A logistic regression and a classification tree are performed.•Evidence for at least 8 effects is found in an extensive corpus study.•Underlying principles are autonomy, subject accessibility and verbality.•Results are explained in terms of clausality and differential infinitive marking.

This paper investigates the alternation between the Portuguese inflected and uninflected infinitive in adverbial contexts on the basis of extensive corpus analyses and from a cognitive-functional perspective. We propose a multifactorial analysis of several variables that could influence the choice between both infinitives. These variables are inscribed within three underlying principles proposed in former literature: higher autonomy of the infinitival clause, lower infinitival subject accessibility and stronger verbality of the infinitive would lead to an increased use of the inflected form. Both a classification tree and a logistic regression analysis offer converging evidence for the validity of autonomy and subject accessibility: infinitival clauses are more prone to the use of an inflected infinitive when they show more semantic–syntactic autonomy and when their subject is less accessible. As for the verbality principle, we found a difference between morphosyntactic and semantic verbality: infinitives that have explicit morphosyntactic marks of their verbal status are indeed more easily inflected. However, contrary to expectations, infinitives that are semantically less prototypical verbs (states and less dynamic verbs), are more easily inflected. We interpret these findings in terms of the “Differential Infinitive Marking” (analogous to differential object/subject marking) and clausality: the inflected infinitive marks the clausal nature of the infinitive construction.