The actualization of language change unfolds gradually across linguistic environments. Over the past decade, there has been growing recognition that actualization is largely driven by similarity-based generalizations-that is, by analogy (De Smet, 2012b). Moreover, frequently used structures often serve as analogical models, exerting a 'gravitational pull' that attracts other structures (De Smet, 2012a, p. 72). In other words, actualization through similarity-based generalizations is largely steered by frequency effects, and actualization hinges on usage and experience with language use. In this talk, I address a somewhat overlooked aspect of actualization theory, namely that the input structures that are most frequent in one community may differ from the most frequent structures in another community (see also Fischer 2013, p. 528). Granted that analogy is sensitive to frequency effects, this discrepancy in input frequency of structures could, hypothetically speaking, result in variations in the substructures guiding the course of actualization across different varieties of a language (see e.g. Grafmiller et al., 2018; Röthlisberger et al., 2017; Verhagen et al., 2018; Barking et al., 2022). Since the cross-varietally potentially variable composition of probabilistic grammars has not yet been incorporated into actualization theory, the extent to which a determined course of actualization is community-specific cannot be predicted by actualization theory in its current form.

To address this issue, I adopt a usage-based perspective on actualization. I hypothesize that if domain-general cognitive mechanisms and processes along with usage factors steer the course of actualization, they should operate similarly across varieties of a language. This, in turn, would mean that the mapping out of change across linguistic contexts should largely align cross-varietally. To test this prediction, I analyze an instance of ongoing syntactic change in Spanish, namely the conventionalization of definite articles in oblique relative clauses (la casa en que nací vs la casa en la que nací, 'the house in which I was born'). Approximately 8000 oblique relative clauses from 19th-20th century Argentinean, Peruvian, and Colombian Spanish are analyzed using mixed-effects logistic regression to test the influence of cognitive and usage-determined factors, viz. the CONSTRUCTIONAL PREDICTABILITY of the antecedent lexeme, the NUMBER and LEVEL OF DETERMINATION of the antecedent, the DISTANCE between the antecedent and the relative clause, and the TYPE OF RELATIVE CLAUSE. Under a usage-based view of the actualization of this change (cf. supra), the prediction is that the new longer form should first be used to convey less accessible (e.g. unpredictable) meanings (Levshina, 2022: 135), and that, over time, the new form diffuses across contexts along similarity-based generalizations by spreading gradually across low-accessibility contexts towards high-accessibility contexts. Crucially, actualization should unfold in a similar manner in different varieties of a language.

The results confirm this hypothesis by showing that, in all of the analyzed varieties, change is initiated and led in contexts involving low accessibility. Over time, the new variant spreads significantly to contexts involving high-accessibility antecedents (e.g. adjacent, definite, singular, higher-frequency antecedents, and restrictive clauses). These findings provide robust support for a usage-based view on actualization with a strong cognitive commitment.