A Test of the Relation between Working-memory Capacity and Syntactic Island Effects

The source of syntactic island effects has been a topic of considerable debate within linguistics and psycholinguistics. Explanations fall into three basic categories: grammatical theories, which posit specific grammatical constraints that exclude extraction from islands; grounded theories, which posit grammaticized constraints that have arisen to adapt to constraints on learning or parsing; and reductionist theories, which seek to reduce island effects to non-grammatical constraints on the human sentence parser, such as limited processing resource capacity. In this paper, we present two large-scale studies designed to test the fundamental prediction of one of the most prominent reductionist theories: that island effects should vary as a function of processing resource capacity. We tested over 300 native speakers of English on four different island effect types (Whether, Complex NP, Subject, and Adjunct) using two different acceptability rating tasks (7-point scale and magnitude estimation) and two different measures of working memory capacity (serial recall and n-back). We find no evidence of a relationship between working memory capacity and island effects using a variety of linear regression techniques including bootstrap resampling simulations: individual differences in memory capacity tended to account for only 0% to 2% of the variance in the strength of island effects. These results suggest that island effects are more likely to be due to grammatical constraints or grounded grammaticized constraints than limited processing resource capacity.