Syntactic parsing and working memory: The effects of syntactic complexity,reading span, and concurrent load

Event-related brain potentials (ERPs) and behavioural measures (reaction ti mes and errors) were used to study the potential effects of individual diff erences in verbal working memory capacity (low vs. high reading span) and a concurrent verbal working memory load (low vs. high load) on the processin g of sentences with a local syntactic ambiguity in German. The sentences we re disambiguated at the clause-final auxiliary to either a subject relative (SR) clause or to an object relative (OR) clause. The processing difficult y for the OR as compared to the SR clauses was reflected in worse off-line comprehension performance, particularly for low span readers. Moreover, ERP s time-locked to the disambiguating auxiliary showed an early posterior pos itivity between 200-350 ms for OR clauses as compared to SR clauses for hig h span readers. Low span readers, in contrast, showed a late frontal positi vity between 500 and 800 ms. While the early positivity for high span reade rs was independent of the concurrent load, the late positivity varied as a function of concurrent load, being delayed in the high load condition. Thes e results indicate that syntactic processes in language comprehension are r elated to individual differences in parsing strategies.