De Lisser and Durleman’s first chapter focuses on Bickerton’s hypotheses about language acquisition. Whether articulated in terms of the Language Bioprogram or in terms of default parameter settings of Universal Grammar (1981, 1984, 1999, 2014, 2016), the hypotheses predict that prototypical Creole features will emerge in early stages of child productions. This view thus leads them to expect target-inconsistent utterances during the acquisition of non-Creole languages where such features are not present, and target-consistent utterances in the acquisition of Creole languages. The investigation tests the second of these predictions for negation via an eighteen-month longitudinal study of the spontaneous production of six Jamaican-speaking children between the ages of 18 and 23 months at the start of the research. The findings reveal an absence of target-inconsistent options for the expression of negation, suggesting that children acquiring Jamaican are knowledgeable of the rules governing negation from their earliest negative utterances, be they sentential, constituent or anaphoric. Taken together, these findings suggest that the acquisition of negation in Jamaican follows Bickerton’s predictions, which are also in line with the more general claim that Negative Concord (NC) is a default choice explored in early stages of child grammar regardless of the target (Moscatti 2020; Thornton 2020).

Bakker’s chapter discusses the syntactic development in twin grammars. Twins and other young children are sometimes reported to create their own languages, sometimes called autonomous languages. The grammars of these languages are quite rudimentary, and the lexicon is derived from the language(s) spoken around them. Bickerton claimed that Creoles share structural properties because the languages have been created by children. Bakker looks at the structures of documented autonomous languages and compares them with Creole languages. It appears that the autonomous languages have more in common with pidgins than with Creole languages, structurally, even though they are created by children, like Creole languages. The twin situation influences the rudimentary properties of the autonomous languages.