Charles A. Ferguson’s research while affiliated with Stanford University and other places

... For this work, one relevant hypothesis, as explored by Chaudenson (2001), suggests that the accumulation of the defining characteristics occurred over several waves of second language acquisition, as opposed to being the result of a complete break in transmission of syntax, as suggested by McWhorter (2018) and Thomason and Kaufman (1988). Another line of inquiry explores the extent to which "foreigner talk", which is to say a particular kind of simplified register that people adopt when they feel their interlocutors do not have sufficient competence in the language, may have contributed to certain developments in Creole morphology and syntax (Ferguson, 1981(Ferguson, , 1975. For Portugueseand Spanish-based Creoles, there is a long history of triangulating Iberian versions of foreigner talk with early modern literary stereotypes and contemporary Afro-Hispanic varieties to get an idea of the range of linguistic variation in the early modern Iberian empires (Kihm, 2018;Lipski, 2001). ...

Reference:

Moly\'e: A Corpus-based Approach to Language Contact in Colonial France

... On the one hand, children's early language production is characterized by reduplication: Early babbling typically consists of a repeated sequence of CV syllables (Smith et al., 1989). Also, children's first words tend to appear in a reduplicated form rather than the standard form (Dressler et al., 2005;Ferguson, 1983). On the other hand, reduplication is often considered a feature of child-directed speech (CDS), a speaking style that caregivers use when addressing young children. ...

Reference:

Che-che ('car-car') and chi-chi ('eat-eat'): Reduplication in Mandarin Chinese child-directed speech