The grammaticality asymmetry in agreement attraction reflects response bias: Experimental and modeling evidence.

Memory access mechanisms such as cue-based retrieval have come to dominate theories of the processing of linguistic dependencies such as subject-verb agreement. One phenomenon that has been regarded as demonstrating the role of such mechanisms is the grammaticality asymmetry in agreement attraction, which is the observation that nouns other than the grammatical controller of agreement can influence the computation of subject-verb agreement in ungrammatical, but not grammatical, sentences. This asymmetry is most often accounted for via the dynamics of retrieval interference. We challenge this interpretation, arguing that the asymmetry largely reflects response bias. Three forced-choice judgment experiments show that neutralizing response bias results in a decrease in the size of the grammaticality asymmetry, or its elimination altogether. Together with the response time patterns in these experiments, this result favors an account that attributes attraction effects to a continuous and equivocal representation of number, rather than to the dynamics of retrieval interference. We implement a model of grammaticality judgments that links a continuous representation of number to the rate of evidence accumulation in a diffusion process. This model accounts for the presence or absence of the grammaticality asymmetry through shifts in the decisional starting point (i.e. response bias), and highlights the importance of monitoring for response bias effects in judgment tasks.