Categorical acquisition: parameter-setting in Universal Grammar

Two triggering models of parameter-setting, the Hierarchical Acquisition model endorsed by Baker (2001, 2005) and Wexler’s (1998) Very Early Parameter Setting model, are compared with Yang’s (2002, 2004) Variational model. The Variational model employs statistical learning mechanisms for parameter-setting. Parameter values compete, with delays occurring when the critical input is sparse. Given the uniformity assumption, children in the same linguistic community undergo a similar, gradual development. On the Hierarchical Acquisition model, children initially choose either parameter value, with potential delays arising from hierarchical ordering of parameters. Change is precipitous when initiated. To adjudicate between models, we conducted a longitudinal study of 4 children, ranging from 1;9 to 2;1 at the start of the study, who were in the throes of setting two interlocking parameters governing inflection and negation. Different developmental patterns were observed depending on initial parameter value, and parametric change was precipitous, as anticipated by triggering models.