The man_i left t_i without a trace: A case study of aphasic processing of empty categories

Abstract

We present the case of an aphasic patient who shows a selective impairment in interpreting syntactic structures on a test of sentence comprehension involving object manipulation. KG makes errors in assigning the antecedents of phonologically empty NPs called traces (Chomsky, 1982 a,b) in sentences like John seems to Bill to be shaving. He is significantly better at choosing the correct antecedent of another type of empty NP, namely subject- and object- controlled PRO (John persuaded Bill to shave, John promised Bill to shave). He has no trouble choosing the correct antecedents of overt pronouns and reflexives and shows no difficulty with syntactic structures that do not contain an empty category. His difficulty with trace is apparent in sentences which have a certain degree of complexity. He also misassigns the antecedent of subject-controlled PRO under one condition: when an overt reflexive or pronoun has PRO as its antecedent (John promised Bill to shave himself). The pattern of impairment suggests that KG cannot utilise one part of a parser/interpreter specifically devoted to the identification and co-indexation of empty categories when other processing demands are high, due to a specific impairment to this component, a capacity limitation, or both. The data support a theory of syntactic structure and parsing which incorporates different types of empty categories.