Working memory constraints on syntactic processing: An electrophysiological investigation

Event-related potentials (ERPs) and reaction times (RTs) were used to study how the processing of sentences with morphosyntactic violations is constra ined by working: memory (WM) capacity. The available WM capacity was varied by three orthogonal manipulations: (I) syntactic complexity; (2) additiona l WM load; and (3) vel-bal WM span. The processing of the morphosyntactic v iolations was reflected in longer RTs in ungrammatical compared with gramma tical sentences, and in an anterior negativity and a centroparietal positiv ity in the ERPs. While the behavioral grammaticality effect was not influen ced by the WM manipulations, the ERP effects were. The amplitude of the ant erior negativity was modulated by the combination of complexity and load, a nd by WM span. The onset of the centroparietal positivity was delayed in th e high-load condition, and for the low-span group. ERPs over the course of the sentences showed a frontal negative slow wave under high WM load, large st for the low-span group. The finding that online syntactic processing is related to WM span and to additional WM load does not support the theory th at there is a WM capacity specific for syntactic processing.